University of Ghana http://ugspace.ug.edu.gh ASSESSMENT OF QUALITY MANAGEMENT SYSTEM IN SOME SELECTED DIAGNOSTIC MAMMOGRAPHY UNITS IN ETHIOPIA BY MEKDES ADMASSU MELKAMU (ID: 10633005) A THESIS SUBMITTED TO THE DEPARTMENT OF MEDICAL PHYSICS SCHOOL OF NUCLEAR AND ALLIED SCIENCES UNIVERSITY OF GHANA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF MASTER OF PHILOSOPHY DEGREE IN NUCLEAR SCIENCE AND TECHNOLOGY JULY, 2019 i University of Ghana http://ugspace.ug.edu.gh DECLARATION This thesis is the result of research work carried out by Mekdes Admassu Melkamu in the Department of Medical Physics, School of Nuclear and Allied Sciences, University of Ghana, under the supervision of Prof. C. Schandorf as the Principal supervisor and Prof. Mary Boadu as the Co-supervisor. I hereby affirm that, no part of this work has been presented in part or whole to any other University or institution for the award of a diploma, or degree at any level. Accordingly, other works and/or researches done by other researchers cited in this work have duly been acknowledged under references. ……………………… Mekdes Admassu Melkamu Date ……………………… (STUDENT) ……………………… Prof. C. Schandorf. Date……………………… (PRINCIPAL SUPERVISOR) ……………………… Prof. Mary Boadu Date……………………… (CO-SUPERVISOR) ii University of Ghana http://ugspace.ug.edu.gh ABSTRACT This research work was aimed at assessing the quality management system and radiation protection of patients of four mammography facilities in Ethiopia. A questionnaire was designed to collect data to assess the status of the quality management systems at the facilities. Quality control measurements were done to verify whether the mammography machines were performing self- consistently compatible with National and International standards. The status of patient protection was evaluated by assessing the mean glandular dose with ACR Phantom in conjunction with image quality assessment using ACR accredited phantom and Leeds test object. From the analysis of the questionnaires administered the facilities did not meet the quality management system criteria. The mammographic machines performed self –consistently with respect to all the parameters tested expect with facility D which recorded a high deviation of ± 57.21% at 30 kV outside the acceptance criterion. The beam qualities were acceptable except one facility which could not meet the criteria with a HVL value of 0.29 mmAl. The image quality assessments of the four facilities were within the acceptance criteria for detectability of microcalcification, masses, fibers and spatial resolution. Estimated mean glandular dose (MGD) of values 1.0 mGy, 1.03 mGy, and 0.96 mGy at 28 kV for the selected facilities were less than the 2 mGy and 3 mGy recommendations by International Atomic Energy Agency (IAEA) and American College of Radiology (ACR) respectively. Management of the mammography facilities must establish an efficient and effective quality management system which includes plan and do (quality assurance), check (quality control) and take action (quality improvement) to govern the imaging process ensuring optimum radiation protection of the patient. iii University of Ghana http://ugspace.ug.edu.gh DEDICATION I dedicated this thesis to The Almighty God and all my Families members. iv University of Ghana http://ugspace.ug.edu.gh AKNOWLEDGEMENTS I would like to thank and acknowledge the General Director of Ethiopian Radiation Protection Authority, Mr. Solomon Getachew, who offered me the opportunity to be trained at University of Ghana. I also express my gratitude to International Atomic Energy Agency (IAEA) for the sponsorship of this program. I would like to acknowledge the Dean of SNAS, Prof Yaw Sorfor-Armah, the Head of International Programs, Dr. Dennis Adotey and the entire staff of SNAS for their valuable support for the successful completion of my work. My special thanks go to my lecturers, especially Prof. C. Schandorf my principal supervisor, Prof. Mary Boadu and Mr. Emmanuel Akrobortu; my co-supervisors who guided, encouraged and supported me for the successful compilation of my study and thesis work. Finally I wish to extend my gratitude to Mr. Biruk Alemu, Senior Radiation Protection Officer in ERPA, for his indispensable help in the collection my data. To all my families for your support and encouragement, I say thank you. v University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENTS DECLARATION .................................................................................................................................. ii ABSTRACT ........................................................................................................................................ iii AKNOWLEDGEMENTS ...................................................................................................................... v TABLE OF CONTENTS....................................................................................................................... vi LIST OF TABLES ................................................................................................................................ ix LIST OF FIGURES ............................................................................................................................... x LIST OF ABREVIATIONS.................................................................................................................... xi CHAPTER ONE .................................................................................................................................. 1 INTRODUCTION ................................................................................................................................ 1 1.0 Overview ............................................................................................................................... 1 1.1 Background of the Study ..................................................................................................... 1 1.2 Statement of the Problem .................................................................................................... 4 1.3 Objectives ............................................................................................................................. 4 1.3.1 Main Objectives ............................................................... Error! Bookmark not defined. 1.3.2 Specific Objectives .......................................................... Error! Bookmark not defined. 1.4 Relevance and Justification ................................................................................................. 5 1.5 Scope and Delimitation ........................................................................................................ 5 1.6 Organization of the Study ................................................................................................... 6 CHAPTER TWO ................................................................................................................................. 7 LITERATURE REVIEW ........................................................................................................................ 7 2.0 Overview ............................................................................................................................... 7 2.1 Overview of Quality Management System in Medical Imaging ...................................... 7 2.2 International Standards for Mammography QA/QC ....................................................... 8 2.3 Dosimetry in Mammography ............................................................................................ 10 2.4 Mean glandular dose.......................................................................................................... 10 2.5 Image Quality in Mammography ..................................................................................... 11 2.6 Optimization of Patient Protection in Mammography ................................................... 12 CHAPTER THREE ............................................................................................................................. 14 vi University of Ghana http://ugspace.ug.edu.gh Materials and Methods .................................................................................................................. 14 3.0 Overview ............................................................................................................................. 14 3.1 Materials ............................................................................................................................. 14 3.1.1 Mammography machine ............................................................................................... 14 3.1.2 Polymethylmethacrylate (PMMA) phantom ................................................................. 16 3.1.3 Leeds test objects (TORMAX) ..................................................................................... 17 3.1.4 MagicMax Dosimetry ................................................................................................... 17 3.1.5 ACR (The American College of Radiology) Mammography Accreditation Phantom . 18 3.2 Methods ............................................................................................................................... 19 3.2.1 Administration of Questionnaire ................................................................................... 20 3.2.2 Quality Control (QC) Tests ........................................................................................... 21 3.2.2.1 Unit assembly evaluation ........................................................................................... 21 3.2.2.2 kVp Accuracy ............................................................................................................ 21 3.2.2.3 kVp Repeatability ...................................................................................................... 22 3.2.2.4 Output Linearity ......................................................................................................... 23 3.2.2.5 Output Repeatability .................................................................................................. 24 3.2.2.6 Half value layer (HVL) .............................................................................................. 24 3.2.2.7 Thickness Compression test ....................................................................................... 25 3.2.2.8 Automatic exposure control (AEC) Test ................................................................... 26 3.2.3 Image Quality ................................................................................................................ 26 3.2.3.1 Image Quality Test ..................................................................................................... 26 3.2.3.2 Spatial resolution test ................................................................................................. 26 3.2.4 Mean Glandular Dose Estimation (MGD) .................................................................... 27 CHAPTER FOUR .............................................................................................................................. 29 RESULT AND DISCUSSIONS ............................................................................................................ 29 4.0 Overview ............................................................................................................................. 29 4.1 Results from Questionnaire .............................................................................................. 29 4.2 Quality Control Test .......................................................................................................... 35 4.2.1 kVp Accuracy and repeatability .................................................................................... 37 4.2.2 Half Value Layer ........................................................................................................... 38 4.2.3 Output Repeatability and Linearity ............................................................................... 39 4.2.4 Automatic Exposure Control (AEC) test ...................................................................... 40 vii University of Ghana http://ugspace.ug.edu.gh 4.3 Image quality tests ............................................................................................................. 40 4.4 Estimation of Mean Glandular Dose ................................................................................ 41 CHAPTER FIVE ................................................................................................................................ 48 CONCLUSION AND RECOMMENDATION ....................................................................................... 48 5.0 overview .............................................................................................................................. 48 5.1 Conclusion .......................................................................................................................... 48 5.2 Recommendation................................................................................................................ 49 5.2.1 For Management of Mammography Facilities .............................................................. 49 5.2.2 For Regulatory Authority .............................................................................................. 50 REFERENCES ................................................................................................................................... 51 APPENDICES ................................................................................................................................... 55 viii University of Ghana http://ugspace.ug.edu.gh LIST OF TABLES Table 3.1: Specification of selected Mammography units ...............................................15 Table 4.1: Mammography performance of QMS .............................................................34 Table 4.2: Unit Assembly Evaluation ..............................................................................36 Table 4.3: Result of kVp Accuracy....................................................................................37 Table 4.4: Result of kVp Repeatability .............................................................................38 Table 4.5: Result of Half value layer (HVL) .....................................................................39 Table 4.6: Result of output linearity and repeatability ......................................................39 Table 4.7: Image quality test result ...................................................................................40 Table 4.8: Result of Facility A Entrance Surface Air Kerma (ESAK) .......................... 42 Table 4.9: Result of Facility B Entrance Surface Air Kerma (ESAK) .......................... 43 Table 4.10: Result of Facility C Entrance Surface Air Kerma (ESAK) ........................ 44 Table 4.11: Result of Mean Glandlunar Dose (MGD) Estimation ................................ 45 Table 4.12: Comparison of Estimated Mean Glandlunar Dose (MGD) at 28kVp with International Atomic Energy Standard (IAEA) and American College of Radiology (ACR) standards .................................................................... 46 ix University of Ghana http://ugspace.ug.edu.gh LIST OF FIGURES Figure 3.1: Picture of mammography unit .......................................................................16 Figure 3.2: Image of PMMA Phantom ..............................................................................16 Figure 3.3: Image of Leeds Test Object (TORMAS) .......................................................17 Figure 3.4: Image of MagicMax Meter .............................................................................18 Figure 3.5: ACR Mammography Accredited phantom .....................................................19 Figure 4.1: Performance of QMS percentage ...................................................................35 Figure 4.2: A graph of entrance surface air kerma with tube voltage of facility “A” ......43 Figure 4.3: A graph of entrance surface air kerma with tube voltage of facility “B” .......44 Figure 4.4: A graph of entrance surface air kerma with tube voltage of facility “C” .......45 Figure 4.5: Comparison of Estimated Mean Glandlunar Dose with Those of American College Of Radiology (ACR) and International Atomic Energy Agency .........................47 x University of Ghana http://ugspace.ug.edu.gh LIST OF ABREVIATIONS AEC Automatic Exposure Control ACR American College of Radiology ALARA As Low as Reasonably Achievable AH Adama Hospital, Adama, Ethiopia Ag Silver BSS Basic Safety Standard COV Coefficient of Variation CR Computed Radiography DR Digital Radiography DRLs „Diagnostic Reference Levels‟ ESAK „Entrance Surface Air Kerma‟ ERPA Ethiopian Radiation Protection Authority EC European Commission GE General Electric GAEC Ghana Atomic Energy Commission GH Girum Hospital, Addis Ababa, Ethiopia HHS US. Department of Health and Human Service HVL „Half Value Layer‟ IAEA „International Atomic Energy Agency‟ ICRP „International Commission of Radiological Protection‟ kV Kilovoltage kVp Nominal tube voltage or tube Voltage peak xi University of Ghana http://ugspace.ug.edu.gh kVnom Tube Voltage set kVpmea Measured Tube Voltage ICMCH ICMC Hospital, Addis Ababa, Ethiopia ISO International Standard Organization lp/mm Line pairs per millimeter mAs Milliampere seconds MGD Mean Glandular Dose Mo/Mo Molybdenum/Molybdenum Mo/Rh Molybdenum/Rhodium Max Maximum Min Minimum NCI Nuclear Cancer Institute NCRP „National Council on Radiation Protection and Measurements‟ NO INF No Information OD Optical Density PMMA Polymethylmethacrylate. ROI Region of Interest SD Standard Deviation STGH Saint Gabriel Hospital QMS Quality Management System QA Quality Assurance QC Quality Control xii University of Ghana http://ugspace.ug.edu.gh CHAPTER ONE INTRODUCTION 1.0 Overview This section provides a brief background to the study, the statement of the problem, the research objectives, relevance and justification, the scope and delimitation of the study, and the organization of the study. 1.1 Background of the Study Diagnostic radiology is a practice in which external radiation beams (X-ray) are used to produce an image for the purpose of either diagnosing, excluding or evaluating the course of the disease or pathological conditions. Mammography is used in medical diagnosis or screening of breast. In mammography examinations patients are exposed to low energy of X-rays. The procedure involves the use of specialized screen-film imaging system to deliver low doses to patients [1, 2]. The specialized screen film includes single thin intensifying screen and single emulsion film. The optimized screen-film system ensures that the image sharpness is maximized with high contrast or spatial resolution. In mammographic imaging procedure, the total absorbed dose to the patient should be kept as low as possible whilst maintaining an adequate image quality [3]. Special attention is taken during X-ray examinations to use the lowest radiation dose possible while producing the best images for evaluation. National and international organizations continually review and update the technique standards used by radiology 1 University of Ghana http://ugspace.ug.edu.gh professionals to minimize the dose to patients. Current X-ray systems have very controlled X-ray beams and dose control methods to minimize scatter radiation. This ensures that those parts of a patient's body not being imaged receive minimal radiation exposure [4, 9]. In mammography, there are two types of examinations performed, screening and diagnostic examinations. Screening mammography is carried out on age based asymptomatic women in order to detect unsuspected breast cancer, to reduce breast cancer mortality. In early detection of breast cancers, it has a greater role because it can show changes in the breast up to two years before a patient or physician can feel them. According to current guidelines of U.S. Department of Health and Human Services (HHS) and the American College of Radiology (ACR) screening mammography is recommended every year for women, beginning at age 40. Research has shown that annual mammograms lead to early detection of breast cancers, when they are most curable and breast-conservation therapies are available. For women who have higher risk of cancer due to family history, the National cancer institute (NCI) suggests such women to seek expert medical advice about whether they should begin screening before age 40. Diagnostic mammography is used to evaluate a patient with abnormal clinical findings such as a breast lump or nipple discharge that have been found by the woman or her doctor. Diagnostic mammography may also be done after an abnormal screening mammogram in order to evaluate the area of concern on the screening exam [4, 5]. The risk of radiation-induced cancer, carcinogenic associated with mammography, is considered acceptable compared to the expected benefits. In order to get good contrast 2 University of Ghana http://ugspace.ug.edu.gh and high resolution diagnostic image with an optimized radiation exposure, quality assurance or quality control program is essential in relating to specific test on the mammographic equipment, image quality assessment, consistency test, and radiation dose measurement. The quality assurance program of diagnostic facility should include mammography techniques to minimize radiation doses without compromising the image quality [6, 7, and 8]. The assessment of doses and image quality from mammographic examinations has been complex due to imaging of dense glandular breasts as well as differentiating presentation of benign or malignant tissues. In a single examination, a number of factors such as the breast thickness, composition, beam quality, film processing unit, breast compression device and geometry of the imaging system are considered. Because of the importance of mammography in accurately diagnosing breast cancer, particularly in early stage cancers, and reducing its high mortality rate in women, it is essential that all mammograms be performed and interpreted with the highest possible quality standards. The existence of and strict adherence to quality assurance (QA) and quality control (QC) measures and guidelines must be practiced in all mammography facilities in order to assure the most accurate diagnoses for all patients. Quality assurance (QA) refers to all of the planned and systematic actions that instill confidence that valid mammography studies are being performed, including everything from the recruitment of patients to assessment of outcome data. Quality controls (QC) are activities to check whether the equipment is performing self-consistently and planned activities are performed to meet prescribe image quality criteria with optimized dose to the patients. 3 University of Ghana http://ugspace.ug.edu.gh Ensuring quality in patient care is a challenge requiring a team approach. The primary members of the mammography team include the radiologist, technologist, and physicist [10]. 1.2 Statement of the Problem Literature shows that in order to attain clinically acceptable diagnostic image with an optimized radiation dose to patients , quality management system is essential to effective planning, using equipment that is performing self-consistently and checking whether equipment is delivering optimum doses consistently with acceptable image quality. Currently in Ethiopia I have not found documented research on quality management system for diagnostic mammography practice for private or government hospitals/clinics. Quality management system that meets ISO standards should include Quality assurance (plan and do), quality control (check) and Act (quality improvement). This research work seeks to bridge this knowledge gap by assessing the status of quality management including patient dose assessment in place at some selected mammography units in Ethiopia. 1.3 Aim Assess quality control measurement on some selected mammography units in hospital in Ethiopia and to verify self-consistent in line with national and international standards and Assess the status of the quality management system for some selected mammography units in Ethiopia weather it is in the standard or not. 4 University of Ghana http://ugspace.ug.edu.gh 1.3.1 Objectives The objectives of the study were:-  Evaluate the status of the quality management systems at the selected mammography facilities.  Estimate the Mean Glandular Dose (MGD) to patients using the Entrance Surface Air Kerma (ESAK) without backscatter approach.  Make appropriate recommendation from the findings. 1.4 Relevance and Justification This research is relevant because it will:  Assist in assessing the status of the quality assurance (QA) and quality control (QC) measures in place at the selected mammographic units in Ethiopia.  Assist in formulating guidelines for effective use of these mammography units for diagnosis procedures.  Provide reference information for Ethiopia, about the level of equipment performance, imaging protocols and radiation dose to patient undergoing diagnostic mammography. 1.5 Scope and Delimitation The work was carried out at four (4) selected diagnostic mammography units in the Hospital/clinic. The study were examined the implementation of QMS in various facilities, performing quality control on the mammography units by verifying if their 5 University of Ghana http://ugspace.ug.edu.gh performance and output meets in international standards, the assessment of estimating the MGD to patient by using ESAK without backscatter approach were performed and compared with the international standard. 1.6 Organization of the Study The thesis contains five chapters. Chapter one provides the statement of the problem, research objectives, justification and relevance of the study, scope of the study and delimitation. It also provides the outline of the thesis. Chapter two is focused on literature review relevant to the research problem. Chapter three deals with the materials and methods for the conduct of the research work. Chapter four presents the results and discussion. Chapter five presents the conclusions of the study and recommendations from the findings. 6 University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO LITERATURE REVIEW 2.0 Overview This chapter outlines literature review relevant to the research work. 2.1 Overview of Quality Management System in Medical Imaging Fast developments of medical imaging show a resulting need for appropriate and high quality anatomical information of the subject‟s body. The performance and financial circumstances of radiology departments may be compromising the quality of patient care because of low appreciation of quality management system in operational efficiency, image quality and patient radiation dose [9]. A quality management system (QMS) is an important tool with the objective of continuous quality improvement to support the operation of medical imaging facility. Quality management system contains objective and polices of the facilities; documented procedures; written work instructions; monitoring, recording and auditing of the system [14, 16]. A good quality management system is important to patient protection and efficient running of a medical imaging facility, providing quality clinical images while maintaining patient and staff radiation dose as low as reasonably achievable (ALARA). Quality management system contain all aspects of medical imaging technology for example room and work flow design, equipment selection and purchase, installation, acceptance test, commissioning test , quality control test, equipment maintenance and the disposal of equipment at the end of its useful life time. There is a need to benchmark the 7 University of Ghana http://ugspace.ug.edu.gh level of quality management systems to provide evidence-based records aimed at improving protection and safety and ensuring quality imaging. Important principles that medical physicist, who is the one responsible for overall system quality must understand all of the essential elements of a quality management system and have the ability to design the structure of such systems. The key to quality management is a good understanding of the basics, including the concepts of quality assurance, quality control, and continuous quality improvement. Quality assurance (QA) is a management tool which, through the development of policies and the establishment of review procedures, aims to ensure that every X-ray examination is necessary and appropriate to the medical problem. It includes patient dose evaluation, quality control of the X-ray system, documented policies, training and continuing education of staff, clinical audit and procedures for remedial actions. Quality control (QC) on the other hand is the technical part of quality management system that deals with the instrumentation and equipment used by the radiographers of a facility. It contains the techniques used in monitoring and maintenance of the system elements that can affect the quality within the mammography program. Quality management comprises activities and functions undertaken by management in the determination of quality policy and its successful implementation through ways including quality assurance and quality control. 2.2 International Standards for Mammography QA/QC An efficient approach for evaluating performance of QMS can be attained through the implementation of a QA program. QA delivers a background for continuous 8 University of Ghana http://ugspace.ug.edu.gh improvement through a feedback mechanism. It provides the way to identify nonconformities from optimum performance of mammographic unit, best diagnostic practice and training needs [31]. Different organizations like the International Atomic Energy Agency (IAEA), European Commission (EC) and American College of Radiology (ACR) have developed and published QA programs and QC requirements used for facilities performing mammography procedures [26, 27]. These manuals have been adopted by other organizations and countries to ensure quality within the mammography procedures and related programmes enhancing the protection and safety of patient. The IAEA standard [14,16] covers the information about the QA programme for screen/ film (SF) and digital radiography (DR). In the two standards published information listed in quality assurance in screen film mammography also includes digital mammography. The documents cover all required standards for mammography quality assurance program through which high quality imaging can be achieveed. The two IAEA HHS standards highlight the following elements: well-trained and experienced personnel (radiologist, radiographer, and medical physicist), well designed equipment, equipment in good working order, proper positioning and technical factors for exposure and appropriate image viewing conditions [14, 16]. The EC standard is minimum requirements to implement throughout the EC member states. It is not meant to reduce the applicability of the quality control formulated by local or national QA programs. The purpose of the guide line is to show the basic procedures, dose measurements and their frequencies [23]. 9 University of Ghana http://ugspace.ug.edu.gh ACR protocol establish a manual for mammography in terms of indications like screening and diagnostic, qualification and responsibility of personnel, specification of examination, documentation and communication of results ,equipment specification, mobile and telemammographic settings, radiation safety in imaging, quality control and improvement [1,36]. 2.3 Dosimetry in Mammography In mammography there is a significant risk of developing cancer, no matter the amount of radiation dose. In the procedure, low energy X-ray is used. To ensure the application of basic principle of radiation protection (justification and optimization) the dose to breast needs to be assessed. Assessing the dose delivered to the breast helps to evaluate the performance of the imaging system and also estimates the risk of patients undergoing mammography procedures. 2.4 Mean glandular dose The mean glandular dose is average dose in glandular tissue. Breast contains adipose and glandular tissues, and the beginning of breast cancer is normally from glandular tissue within the breast [22]. Due to this reason the assessment of the amount of radiation dose delivered to the glandular tissues or the breast is used to estimate the risk of patients undergoing mammography for breast cancer. The mean glandular dose (MGD) is the approved dosimetric quantity by organizations like the International Commission on Radiological Protection (ICRP) and the United States National Council on Radiation Protection and Measurements [xxx]. The quantities has been adopted by other 10 University of Ghana http://ugspace.ug.edu.gh organizations like EC (European Commission) and ACR (American College of Radiology) and have been used in their protocols [22]. Evaluating dose to the breast is an important component of a quality control programme which must be implemented in every facility performing mammography procedures. In accordance with the radiation protection principle, radiation exposures must be kept as low as reasonable achievably [23]. The mean glandular dose depends on the tube voltage, thickness and composition of the breast. It is also affected by half value layer (HVL) and X-ray target material. Because of the difficulty of estimating mean glandular dose (MGD) directly, the entrance air kerma(ESAK), without backscatter, at the upper surface of the breast is determined and the MGD is estimated by multiplying by appropriate conversion factors [23] using a standard breast phantom or patients and appropriate conversion factors. The mean glandular dose is calculated using equation (2.1). where ESK is the incident air kerma (without back scatter) at the upper surface of the breast, g is the incident air kerma to mean glandular dose conversion factor (g-factor), c corrects for any difference in breast composition from 50% glandularity and the factor s corrects for any difference due to the use of a different X-ray spectrum. 2.5 Image Quality in Mammography In mammography patient dose and image quality are the main concern. This is because in breast cancer screening, small abnormalities are looked for. Currently 11 University of Ghana http://ugspace.ug.edu.gh three types of image detector are used in mammography: screen-film (SF), computed radiography (CR), and digital radiography (DR), with a growing number of digital (CR and DR) systems [29]. The quality of the breast images depends on the design and performance of the mamographic unit, the image receptor, and on how that equipment is used to acquire and process the mammogram. The diagnostic information is integrally related to the quality of the image and higher image quality will result in more accurate diagnosis. The systematic monitoring of both image quality and radiation dose is needed to ensure a consistent high quality of the mammography examination [10]. Conventional film/screen mammography is being gradually substituted by digital technology in most countries. 2.6 Optimization of Patient Protection in Mammography Due to natural appearance of the breast contents (the adipose and glandular tissues) it is noted that they are more susceptible to radiation [24]. According to the principle stated by the International Commission of Radiation Protection (ICRP) radiological practice justification, dose optimization and dose reference level are essential to patient protection [25]. IAEA adopts those principles in their international basic safety standard (BSS) for the protection against ionizing radiation. The beginning of any radiological practice should be justified. Each examination must outcome in a positive benefit for the patient. When the diagnostic examination has been clinically justified the dose to patient must be optimized. The doses should be as low as reasonably achievable reliable with gaining the suitable quality of image. In mammography optimization for protection, there is significant opportunity in the enhancement of quality image and reduction of dose. In 12 University of Ghana http://ugspace.ug.edu.gh diagnostic procedure optimization does not mean the decrease in dose is the main purpose but ensuring that image quality is not compromised. The BSS and ICRP encourage the use of reference or guidance level as assistance for the optimization in diagnostic practice [27]. 13 University of Ghana http://ugspace.ug.edu.gh CHAPTER THREE MATERIALS AND METHODS 3.0 Overview This chapter describes the materials and methods used for the conduct of the research work. 3.1 Materials The materials used for this research are mammography machines, slabs of semi-circular polymethylmethacrylate (PMMA), a calibrated MagicMax QC kit (iba) with MagicMax multimeter and MagicMax software installed on a laptop, Aluminum foil, the ACR Mammography Accreditation Phantom, Leeds tests object TORMAX, a ruler, a towel ,Microsoft excel software and designed data sheets. 3.1.1 Mammography machine Four selected mammography machines were involved in the research: two computed radiography (CR) systems: facility B and C and two digital radiography (DR) systems: facility A and D. Except for facility D, all the others were from the same city and private hospitals. The selected mammography units used manual exposure system during the procedure while facility C rarely used AEC system. The specifications of mammography equipment (figure 3.1) used are presented in Table 3.1. 14 University of Ghana http://ugspace.ug.edu.gh Table 3.1: Specifications of selected mammography units. FACILITIES CHARACTERISTICS A B C D Type of Equipment DR CR CR DR Manufacturer SINO MDT SIEMENS SIEMENS VARIAN Model SN-DR3 10893687 XM15 M113T Year of manufacturer 26/4/2017 NO INF NO INF JAN,2011 Serial number 5352/70426 30151 65R078 89092 00000 Mode of Operation MANUAL MANUAL MANUAL MANUAL /AEC Anode/Filtration Mo/Mo Mo/Mo Mo/Mo Rh/Ag Combination kVp range 20-35 23-35 23-35 22-39 mAs range 23-630 10-630 10-630 22-252 15 University of Ghana http://ugspace.ug.edu.gh Figure 3.1: Picture of mammography unit 3.1.2 Polymethylmethacrylate (PMMA) phantom Semi-circular slabs of polymethylmethacrylate (PMMA) were used in this study. Each slab has 100 mm of radius. A total of 8 slabs (6 have 10 mm thickness and 2 have 5 mm thickness) were used to simulate the breast. The PMMA is displayed in Figure 3.2. Figure 3.2: Picture of PMMA slabs 16 University of Ghana http://ugspace.ug.edu.gh 3.1.3 Leeds test objects (TORMAX) The Leeds tests object, TORMAX phantom was used in this study to evaluate image quality. It has inside a ten-step wedge, one high-contrast resolution patterns (1.0 to 20.0 lp/mm), a low-contrast resolution pattern, twelve low-contrast large details (5.6 mm diameter, decreasing thickness), 22 high-contrast small details (0.5 mm and 0.25 mm diameter, decreasing thickness, 11 details per each diameter), micro-particles representing micro-calcifications” on a step wedge. The test object is presented Figure 3.3. Figure 3.3: Picture of Leeds test object (TORMAX) 3.1.4 MagicMax Dosimetry The dosemeter used for measurement for this study was newly calibrated MagicMax millimeter iba model 90529 and serial number 03A-13-40173 USB based system together with MagicMax-Meter measurement software connected via laptop or PC. The equipment is manufactured by IBA Dosimetry GmbH in Germany. It was used to measure the kVp, HVL, Exposure or Entrance Surface Air Kerma (ESAK), exposure rate, exposure time measurements. The MagicMax software allows the display of the reading on the laptop/PC. The MagicMax-Meter and the software are shown in Figure 3.4. 17 University of Ghana http://ugspace.ug.edu.gh Figure 3.4: MagicMaX-Meter 3.1.5 ACR (The American College of Radiology) Mammography Accreditation Phantom The breast equivalent phantom used in this study for assessment of image quality was the ACR mammography accreditation phantom composed of three objects. Six fibers (diameters of 1.56 mm, 1.12 mm, 0.89 mm, 0.75 mm, 054 mm and 0.40 mm); five groups of simulated micro-calcifications (diameters of 0.54 mm, 0.40 mm, 0.32 mm, 0.24 mm, 0.16 mm) and five masses (thicknesses of 2.0 mm, 1.0 mm, 0.75 mm, 0.5 mm, 0.25 mm). The ACR Mammography Accreditation Phantom is presented in Figure 3.5. 18 University of Ghana http://ugspace.ug.edu.gh Figure 3.5: ACR Mammography Accreditation Phantom 3.2 Methods The questionnaire administered indicated in Appendix A was designed to collect the responses of experts to evaluate the status and effectiveness of the QMS in place and being implemented by the mammography facilities with the reference of ISO. The data sheet in Appendix B1 was used to collect useful equipment information from each selected facility. Quality control tests were carried out on each mammography unit to verify whether they were performing in accordance with internationally accepted criteria. The QC tests performed included: The unit assembly evaluation, kVp accuracy and repeatability, output linearity and repeatability, Half value layer (HVL), AEC performance and image quality tests. ESAK (Entrance surface air kerma) and MGD (mean glandular dose) were estimated and compared with IAEA and ACR protocols values (16,1). 19 University of Ghana http://ugspace.ug.edu.gh 3.2.1 Administration of Questionnaire The questionnaire was administered (Appendix A) to determine the status of QMS at the selected mammography units. The Administrator who is responsible in each facility was requested to participate and also to answer all questions to facilitate and effective evaluation of the QMS. The set of information requested from the managers or supervisors on quality management system included documentation of policy on quality, description of management systems, accountabilities and levels of authority, procedures and instructions, patient and staff details and quality control assessment frequency. Responsibilities of management including establishment of quality policy and objectives and measures taken by management to monitor, analysis of data, audit and improve processes. The management ensures patients protection needed as well as the fulfillment of regulatory requirements through the use of policy, quality objectives, audit results, analysis of data, corrective and preventive actions and management review. Other responsibilities of management requested include resources available for the implementation of quality management system and whether a quality management committee is in place to monitor and review the quality management system periodically. The responses provided by the facilities, were graded with a score of 1 (fully answered), 0.5 (partially answered) and 0 (not answered) and analyzed. A total of 37 points were allotted. 20 University of Ghana http://ugspace.ug.edu.gh 3.2.2 Quality Control (QC) Tests In order to verify that the mammography units are performing consistently, QC tests were performed. The following are the QC tests that were performed and analyzed and then compared with national and international standards: kVp accuracy and repeatability, Output linearity and repeatability, HVL (half value layer), compression test, AEC (Automatic exposure control) test, and collimation test. 3.2.2.1 Unit assembly evaluation The aim of the assessment was to evaluate the mechanical, functionality and assess the level of the equipment safety. A series of tests and verifications were conducted on the mammography unit information recoded using in Appendix B2. The results obtained for this test are shown in Table 4.2. 3.2.2.2 kVp Accuracy The objective of this test was to verify the accuracy of the kVp. Five exposures for each were taken in the manual mode with a nominal kVp settings normally used in clinical procedures in the range 28-35 kVp and the mAs set at 40mAs. The detector was positioned on the breast support, 40mm (from the chest wall), and centered laterally (the reference point). The readings (measured kVp) were recorded. The kVp accuracy was calculated by finding the percentage deviation of the measurements recorded, in equation (3.1). 21 University of Ghana http://ugspace.ug.edu.gh ………...3.1 Where, kVpnom (the value set on the console) and kVpmeas (the measured value). This percentage deviation is taken as a measure of accuracy. The acceptable range for accuracy is ±5% [14]. 3.2.2.3 kVp Repeatability The objective of this test was to verify the repeatability of the tube voltage (kVp). For this test, two exposures were made in the manual mode with a nominal kVp of 28 kVp and mAs of 40 mAs, with the detector positioned at the reference point. The readings were recorded on a data sheet (Table 2). The two readings can be used to calculate the repeatability but for a more accurate and true result, it is best to use more than three readings. Three additional exposures were therefore made using the same parameters, making a total of five exposures. The kVp repeatability was calculated by finding the Difference (%) of the first two values and the coefficient of variance (COV) of the five readings using equations (3.2) and (3.3). ………………. (3.2) Where, Max (maximum measurement) and Min (minimum measurement). For kVp repeatability the percentage difference should be within the range ≤5% [14]. 22 University of Ghana http://ugspace.ug.edu.gh COV (%) = …………… (3.3) Where, SD (standard deviation of the measurements) and Mean (the mean of the measurements). For repeatability, the COV (%) should be within the range ≤2% [14]. 3.2.2.4 Output Linearity The aim of this test was to assess the linearity of the air kerma for a given mAs. With the output linearity measurement, the set up used was the same as that of kVp accuracy and repeatability. After the five exposures were made in the output repeatability test, the mAs was increased to 80 mAs and then to 120 mAs, while maintaining the kVp at 28 kVp. Two exposures each were made with the two additional mAs values selected. For output linearity the average value of the obtained readings of air kerma was calculated for each corresponding mAs selected and recorded on a data collection sheet. The output linearity was then calculated using equation (3.4). …..……… (3.4) Where, Y1and Y2 (the output values obtained by dividing each average air kerma value by the corresponding mAs). The acceptable linearity of output must be less than 10% [14]. 23 University of Ghana http://ugspace.ug.edu.gh 3.2.2.5 Output Repeatability The aim of this test was to evaluate the repeatability of the air kerma for a given mAs. For output repeatability, a nominal kVp of 28 kVp with mAs of 40 mAs was used to make five exposures, with the output readings recorded. After the five exposures, the mAs was increased to 80 mAs, and two exposures were made and the output recorded. After that, the mAs were increased to 120 mAs, and two exposures made. The output repeatability was then determined by finding the percentage difference (%) and COV (%) using equations 3.2 and 3.3 respectively [14]. 3.2.2.6 Half value layer (HVL) The aim of this test was to confirm that the total filtration of the X-ray beam meet the minimum requirements of the national and international standards. This measurement was done with a kVp of 28 and mAs of 40. The detector was placed at the reference point and the sensitive part of the detector completely covered by the radiation field. The compression paddle was placed half way between the focus and the detector and an exposure made. The reading was recorded on a data sheet. A 0.2 mm of aluminum was placed on it which fully covered the sensitive volume of the detector and an exposure was made. The readings were recorded as well. A 0.1 mm of aluminum was added (total 0.3 mmAl), an exposure made with the same parameters and the readings recorded. Three more exposures were made with the aluminum thickness increased to 0.4 mm, 0.5 mmAl and 0.6 mmAl, and the readings recorded. All the aluminum filters were removed and a final exposure made. This reading was recorded as well. The HVL was then calculated using equation (3.5). 24 University of Ghana http://ugspace.ug.edu.gh [ ] …………………….. (3.5) Where; t1 and t2 (thicknesses (mm) of the filters used), M1 and M2 (average values of the readings measured) and M0 (average value of the reading measured without any added filter). The measured HVL is acceptable when it falls within the range [14]: + 0.03 HVL ……….……………… (3.6) Where, kVp (set value of from the console), HVL (calculated half value result) and c (a factor that compensates the anode/filter combination). 3.2.2.7 Thickness Compression test The aim of this test was to confirm the compression paddle in both manual and automatic mode gives tolerable values. This was done by activating the compression paddle by clinical parameter. It functions and stops at the maximum available force. Recorded the displayed values in the data sheet. The compression thickness was made by aligning 20 mm, 45 mm and 70 mm thickness with the applied compression force between 50 N and 100 N. The measured value was recorded and compared with the displayed value. 25 University of Ghana http://ugspace.ug.edu.gh 3.2.2.8 Automatic exposure control (AEC) Test The objective of this test was to test the repeatability of the AEC. This was done by making ten exposures of 45 mm PMMA slabs in the automatic mode, with the mAs readings recorded. The AEC repeatability was estimated by finding the coefficient of variance (COV) using equation 3.3.For repeatability, the acceptable value of COV should be ≤5% [14]. 3.2.3 Image Quality 3.2.3.1 Image Quality Test Objective of this test was to evaluate the image contrast and image qualities of the mammography units. The ACR Mammography Accreditation Phantom was placed on the breast support aligned with the chest wall and laterally central. Lowering the compression paddle until it touches the phantom. Exposure was taken in the manual mode by selected technical factors. The image was processed and evaluated according to evaluation method [14]. 3.2.3.2 Spatial resolution test The objective of this test was to determine the system high contrast resolution. To verify whether the mammography system can find separately two micro - calcifications. The Leeds test object (TOR MAX) phantom was placed on the breast support aligned with the chest wall and laterally central. The compression paddle was lowered until it made enough contact with the phantom. Exposure was taken in the manual mode by selected technical factors. The image was processed and evaluated according to evaluation method [14]. 26 University of Ghana http://ugspace.ug.edu.gh 3.2.4 Mean Glandular Dose Estimation (MGD) Objective of this dose estimation was to measure ESAK for standard phantom thickness and compare with international available and achievable estimated MGD. The ESAK (entrance surface air kerma) was determined using ACR phantom (4.5 cm ) and an ionization chamber. The phantom was positioned on the breast support and the paddle was lowered until it made enough contact with the phantom. The ionization chamber was placed on the compression paddle in the field of the radiation beam. Using clinically used exposure factors, (5) five exposures were performed at different tube voltages and corresponding tube load values (mAs). The exposure readings and used exposure factors were recorded. The exposure readings and the corresponding tube voltage (kV) parameters were used to plot an exponential graph for each facility (Figures 4.2-4.4). From the graph the entrance surface air kerma (ESAK) was calculated using the generated equation curve for each facility. The mean glandular dose for a standard breast (45 mm) was determined. Using the estimated entrance surface air kerma and the relevant conversion coefficients, the mean glandular dose was calculated using equation 3.7. …………….. (3.7) Where; Kair (entrance air kerma at the surface of the 45 mm thickness of PMMA, measured without backscatter), g (factor that converts the entrance air kerma to the mean glandular dose for the 53 mm thick standard breast), c (conversion factor which allows 27 University of Ghana http://ugspace.ug.edu.gh for the glandularity of the 53 mm thick standard breast) and s (factor which gives a correction that depends on the target filter combination). 28 University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR RESULT AND DISCUSSIONS 4.0 Overview This chapter presents the results obtained from the questionnaire administered, the Quality control test performed as well as the discussions of the findings. 4.1 Results from Questionnaire The study was performed in four selected mammography facilities within the Addis Ababa Regional Administration and Adama city in Ethiopia. There are ten (10) facilities performing mammography procedures within the two cities. The studies could not be performed at six of the facilities because management did not permit the study to be carried out at their facilities while some mammography equipment of some facilities were not functional with some technical problems during the study period. All the facilities in the studies are private owned by individuals and organizations. They have been authorized to perform diagnostic mammography procedures by the Notification and Authorization Department of the Ethiopian Radiation Protection Authority (ERPA). It was observed that only one (C) selected facility uses automatic exposure control system during the procedure while the other three (A, B and D) facilities do not use automatic exposure control but select manually the exposure factors. 29 University of Ghana http://ugspace.ug.edu.gh All the facilities have one mammography machine and perform both diagnostic and screening mammography procedures. Facilities A, B, C and D began mammography procedures since 2017, 2015, 2014, and 2015 respectively. All the facilities A, B, C and D have permanent qualified radiographers that perform the imaging procedure and permanent radiologists who examine mammogram of patients and give appropriate diagnosis report to referring clinicians. In the case of self-referred (i.e. patients visiting the facilities for screening purpose) they give advice according to the findings from the examination. When there is an abnormality the patients are referred to a specialist doctor for further examination and diagnosis to verify if the abnormalities are malignant or cancerous or otherwise. According to the QMS and as organizational rule, all the facilities performed acceptance and commissioning tests after installation of the mammography equipment before they are used for clinical services. An acceptance test is performed to verify that the purchased equipment operates safely in accordance with the manufacturer‟s specification and commissioning tests are performed to receive the equipment into clinical use. The results from commissioning used as baseline levels of optimum performance of the equipment. In the case of mammography, optimum exposure settings based on conditions and features such as different breast sizes and thickness are noted during the commissioning test. These established baseline levels such as target optical density serves as guidelines and are subsequently used for quality control measurements. The levels are also used to ensure and maintain the optimum performance of the equipment throughout its use for providing clinical services or procedures. All facilities indicated that acceptance tests were performed after the installation of the equipment before being used 30 University of Ghana http://ugspace.ug.edu.gh for clinical service but had no documentation (copies of the tests) to confirm that the tests were done. And they also had no information as to whether the commissioning tests were performed to establish the baseline levels. All mammography facilities providing radiography services including the mammography units of the selected facilities are managed by qualified Radiologists/ Technologists/ Radiographers. Evaluation the (QA/QC) was divided into three sections. Section one assessed QA policy and documentation, establishment and performance evaluation of the system focusing on document development and effective implementation of quality management system, instructions and procedures which describes functional responsibility, accountability and level of authority, patient protection and safety, and confidentiality and quality control programme. Section two evaluated education and training, continuous improvement of workers and performance. Section three evaluated quality control including availability of QC manual, tests performed, assessment of patient dose, and availability of system for controlling patient‟s dose. It was observed that facilities A, C and D have a documented quality policy and procedure relating to image quality and patients protection, safety and privacy. According to the instruction patients, staff and regulatory authority have access to these documents. Facility B has no documented quality policy or procedures. Facilities A, B,C and D said that they have the narrative of functional responsibilities, accountabilities and levels of authority within the facilities documented as well as a description of the processes and supporting information explaining how work is to be carried out and recorded. 31 University of Ghana http://ugspace.ug.edu.gh Like other medical fields mammography facilities must ensure that patients‟ information and details remain personal, that means patient confidentiality is vital. From the response and observation diagnostic reports from the radiologist/ Technologist in facility A, C and D are sealed and addressed to the physicians who requested the examination. For women who participate in the screening program in the facility the radiologists explain the detail of the diagnostic report and if further medical examination is required they are advised based on the findings. To minimize the occurrence of the repeats of the diagnostic image and to get adequate diagnostic result effective, quality management system is important. To ensure the production of quality image, radiographers of facility A, B and C stated that during procedures they ensure there is enough compression of the breast to reduce motion, good positioning of the breast and patient. Imaging staff select appropriate exposure factors in manual mode. Within the procedure, patients are informed to notify the radiographers when they feel uncomfortable or pain in order to help produce a good image and reduce the occurrence of repeat of procedure due to poor image quality. For effective implementation of quality management system, management must demonstrate their commitment in terms of responsibility by establishing quality objectives, providing appropriate resources to implement the system. In the studies management of facility A, C and D have provided available resources and also develop communication between patients, staff and management to address the issue related to improve the implementation of quality management system that address the requirements and complaints of the patients. 32 University of Ghana http://ugspace.ug.edu.gh In radiographic procedures and activities affecting the quality of patient care, protection and safety, and proper usage of resources and establishment of optimum clinical service are documented and audited by comparing them with a good radiography practice and procedure. This can be achieved by effective implementation of clinical internal and external auditing. From their report and confirmation all the facilities do not have documented procedure to conduct internal audit, reporting result and audit records are not evaluated. So this activity leads to a poor delivery of clinical service. Corrective actions need to be implemented to improve the quality of delivery. In all facilities the radiographers have appropriate records of education, training and experience of the staff. The lowest educational level is diploma in radiography and the highest level Bachelor of Science degree (BSC) in radiography and on the job training makes them competent to perform mammography procedures. Theoretical and practical continuous training for the radiographers are essential to cope with and improve their performance related to breast positioning technique, current development of optimization procedures, radiation protection of patients and personnel involved in the radiology departments. From their response and confirmation, facility A and D additional and continuous training were identified as contributing to quality standards which are maintained and improved. In contrast, facilities B and C were not receiving further education and training. To ensure the quality performance of mammography machine in compliance with acceptable standard regular quality control tests are important. The result from the test must be documented and used as a reference for checking whether the appropriate quality is being maintained to fulfill regulatory requirements. The radiographers should 33 University of Ghana http://ugspace.ug.edu.gh understand requirements of Quality assurance and quality control and be familiar with necessary techniques and knowledge of recording, monitoring, evaluation and taking appropriate corrective actions methods. According to the IAEA Human Health Series 2011[14] the medical physicist is responsible and supervisor for quality control activities. All the facilities had no documented quality control tests and assignment of the responsibilities for radiographers and medical physicist. From their response and confirmation, facilities A and C perform quality control on the machine periodically according to the recommended acceptance criteria that validate the performance of the units. In contrast, facilities B and D were not performing regular quality control with recommended acceptance criteria. Overall performance of the facilities in the establishment and implementation of QMS are indicated in Table 4.1. Table 4.1: overall performance of QMS of mammography units FACILITY QM HR QC OVERALL (%) (%) (%) PERFORMANCE (%) A 93.75 100 73.33 89.03 B 16.65 25 26.67 22.77 C 47.1 25 46.67 39.59 D 18.35 100 26.67 48.34 34 University of Ghana http://ugspace.ug.edu.gh 100 89.03 90 80 70 60 48.34 50 39.59 40 30 22.77 20 10 0 A B C D Facilities Figure 4.1: Performance of QMS in percentage 4.2 Quality Control Test Table 4.2 shows that all the mammography units passed the performance evaluation. The techniques factors used to perform imaging procedures were not available in all facilities. 35 Performance of quality managemnt system (%) University of Ghana http://ugspace.ug.edu.gh Table 4.2: Mammography unit assembly assessment FACILITIES PARAMETERS A B C D Mechanical stability of free-standing unit pass pass pass pass Lights indicator pass pass pass pass Units motion function pass pass pass pass Locks and detents function pass pass pass pass Angulation indicators pass pass pass pass Wobble and vibration pass pass pass pass Image receptors sliding and holding pass pass pass pass during gantry angulation Compression paddle condition pass pass pass pass Automatic compression release pass pass pass pass Operator shielding evaluation pass pass pass pass Safety of patient/operator against units pass pass pass pass Availability of technique parameters chart Fail Fail Fail Fail The results of the quality control assessment performed on mammography units assessment like kVp accuracy and repeatability, output linearity and repeatability, half value layer, and automatic exposure control measurements are presented from Table 4.3- Table 4.7). 36 University of Ghana http://ugspace.ug.edu.gh 4.2.1 kVp Accuracy and repeatability The kVp accuracy of mammography facility A equipment at 28, 30, 32 and 34 were 4.19%, 4.17%, 2.55% and 2.1% respectively. That of facility B at 28, 30 , 32 and 34 kVp were negative 7.38%, 7.21% , 7.57% and 7.34% respectively. Those of facility C at 28, 30 and 32 kVp were -5.45, 5.45 and 4.44 respectively. Facility D at 28 and 32 kVp had an accuracies of negative -53.2%, and 57.21%.The result of A and C fell within the acceptable range of ±5% but the result of B and D fell outside the acceptable range of ±5%. All four facilities recorded kVp repeatability at 28,30,32 and 34 kVps respectively as in A 0.022%, 0.246% ,0.023 and 0.021%, in B 0.312%, 0.021%, 0.02%, and 0.067% in C as 0.027%,0.075%, 0.046% and at the 34 kV setting not working and in D as 0.677%,0.044%, and no response respectively, because of the maximum limit of the measuring device, 60kVp, which also falls within the normal range of kVp coefficient of variation ≤2%. Table 4.3: Results of kVp Accuracy. Measured kVp (%) Nom kVp A B C D 28 26.83+4.19 25.93-7.38 26.48-5.45 42.9-53.2 30 28.75+4.17 27.84-7.21 28.37-5.45 47.16-57.21 32 31.19+2.55 29.58-7.57 30.58-4.44 - 37 University of Ghana http://ugspace.ug.edu.gh 34 34.27+2.1 31.51-7.34 - - Table 4.4: kVp Repeatability results of four mammography units. Measured kVp (%) Nom kVp A B C D 28 0.022 0.312 0.027 0.677 30 0.25 0.021 0.075 0.044 32 0.02 0.02 0.046 - 34 0.021 0.067 - - 4.2.2 Half Value Layer The performance of the X-ray beam produced by the mammography equipment to penetrate the breast (phantom) was evaluated by measuring the half value layer or the beam quality. According to IAEA acceptable criteria, kVp/100 + 0.03≤ HVL ≤ kVp/100 + C, where kVp is the tube voltage value. At 28 kV, facilities B and D recorded the highest and lowest half value layer figures of 0.37 mm Al and 0.29 mm Al respectively. Facilities A and C also recorded half value layers of 0.36 mm Al and 0.34 mm Al. Half value layer figures of 0.29 mm Al was lower by 0.02 from the acceptable limiting values of 0.31 mm Al (kVp/100 +0.03) at 28 kV. Estimated half value layers from facilities A, B and C were within the acceptable range. From the results (Table 4.5) the mammography equipment of the selected facilities showed sufficient filtration of the X-ray beam for optimized patient dose and good quality image production. 38 University of Ghana http://ugspace.ug.edu.gh Table 4.5: Results of Half Value Layer (HVL) Tests Tube Voltage Tube Load Half Value Facility Exposure Mode (kVp) (mAs) Layer (mm Al ) A Manual 28 40 0.36 B Manual 28 40 0.37 C Manual 28 40 0.34 D Manual 28 40 0.29 4.2.3 Output Repeatability and Linearity Facility A output repeatability was 0.77% with an output linearity of 3.12 μGy/mAs, B recorded an output repeatability of 0.03% and a linearity of 0.69 μGy/mAs, C output repeatability 0.32% and linearity 0.44 μGy/mAs and that of D was 0.36% and 5.55 μGy/mAs respectively. Table 4.6: Results of output linearity and repeatability Tests Facility kVp Repeatability (%) Linearity (μGy/mAs ) A 28 0.77 3.12 B 28 0.03 0.69 C 28 0.32 0.44 D 28 0.36 5.55 39 University of Ghana http://ugspace.ug.edu.gh 4.2.4 Automatic Exposure Control (AEC) test The AEC repeatability of A was 0.31%, that of B was 1.06% and C was 0.18%, it showed that all values are within the acceptable range. It confirms that the AEC mode is able to produce suitable image contrast and keep as low as possible the MGD. For the compression tests such as alignment and thickness have been scored correctly by all of the systems. 4.3 Image quality tests The results from subjective analysis tests using the ACR mammography accreditation phantom and the Leeds test objects TORMAX according to IAEA, 2009 are shown in Table 4.7. Table 4.7: Image quality tests results SCORE PER FACILITY TESTS A B C D ACR accreditation Fibers 4 4 4.5 4 Phantom test (tolerance ≥ 4) * Microcalcifications 3.5 3 4 3 (tolerance ≥ 3) * Mass 3.5 3 4 3.5 (tolerance ≥ 3) * Spatial resolution Lines pairs/mm 18 15 18 13 tests (Tolerance ≥ 11 lp/mm) * 40 University of Ghana http://ugspace.ug.edu.gh The results of image quality assessment of the four facilities were satisfactory as it can be seen in the Table 4.7 where A have got 4 fibers, 3.5 micro-calcifications and 3.5 masses for the ACR Accreditation phantom test and 13 lines pairs/ mm for the spatial resolution test. The facility B machine scored for the ACR test, 4 fibers, 3 micro-calcifications groups and 3 masses while the test spatial resolution was 18 lines pairs/mm. The C unit recorded a score of 4.5 fibers, 4 groups of micro-calcification and 4 masses while from the spatial resolution it has got 15 lines pairs/mm. And the facility D scored for the ACR test, 4 fibers, 3 micro- calcifications groups and 3.5 masses while the test spatial resolution was 18 lines pairs/mm. Therefore, all the mammography systems passed the subjective image quality evaluation their score fell within the acceptable range for ACR phantom (≥ 4 for fibers; ≥ 3 for micro- calcifications and ≥ 3 for masses). The spatial resolution test has 11 lp/mm for acceptable limits and 15 lp/ mm for the achievable limit. This means all the systems selected have ability to detect breast tumors and differentiate them from normal tissues. 4.4 Estimation of Mean Glandular Dose International Atomic Energy Agency (IAEA) recommends that for mammography procedures, the mean glandular dose should be < 2.0 mGy and at most < 2.5 mGy per view for a breast phantom thickness of 4.5 cm [16]. Likewise as per the standards of the American College of Radiology (ACR), the mean glandular dose should be < 3.0 mGy [1]. 41 University of Ghana http://ugspace.ug.edu.gh Facility A recorded the highest values of entrance surface air kerma (Table 4.8) and mean glandular dose of 9.52 mGy and 2.01 mGy respectively at 34 kVp and the lowest value of entrance surface air kerma and mean glandular dose of 4.98 mGy and 1.05 mGy at 28kVp. Facility B recorded the highest values of entrance surface air kerma (Table 4.9) and mean glandular dose of 9.14 mGy and 1.96 mGy respectively at 34 kVp and the lowest value of enterance surface air kerma and mean glandular dose of 5.07 mGy and 1.08 mGy at 28kVp.And Facility C recorded the highest values of entrance surface air kerma (Table 4.10) and mean glandular dose of 9.52 mGy and 1.86 mGy respectively at 34 kVp and the lowest value of entrance surface air kerma and mean glandular dose of 5.02 mGy and 0.98 mGy at 28kVp. Table 4.8: Results of facility “A” Entrance Surface Air Kerma (ESAK) tests. kVp ESAKi ESAKcalc MGD 28 4.94±0.005 4.98±0.004 1.05 30 6.12±0.007 6.16±0.007 1.31 32 7.77±0.013 7.66±0.014 1.62 34 9.42±0.014 9.52±0.011 2.01 42 University of Ghana http://ugspace.ug.edu.gh 10 9 8 y = 0.2355e0.1088x 7 R² = 0.9985 6 5 4 3 25 27 29 31 33 35 Tube Voltage (KV) Figure 4.2: A graph of entrance surface air kerma with tube voltage of facility “A” Table 4.9: Results of facility “B” Entrance Surface Air Kerma (ESAK) tests. kVp ESAKi ESAKcalc MGD 28 5.04±0.008 5.07±0.006 1.08 30 6.2±0.007 6.17±0.004 1.32 32 7.63±0.013 7.51±0.02 1.61 34 9.06±0.008 9.14±0.01 1.96 43 Enterance Surface Air Kerma(mGy) University of Ghana http://ugspace.ug.edu.gh 10 9 8 y = 0.3233e0.0983x 7 R² = 0.998 6 5 4 3 25 26 27 28 29 30 31 32 33 34 35 Tube Voltage(kV) Figure 4.3: A graph of entrance surface air kerma with tube voltage of facility “B” Table 4.10: Results of facility “C” Entrance Surface Air Kerma (ESAK) tests. kVp ESAKi ESAKcalc MGD 28 5±0.006 5.02±0.004 0.98 30 6.19±0.017 6.21±0.01 1.21 32 7.81±0.007 7.69±0.016 1.5 34 9.43±0.035 9.52±0.01 1.86 44 Entrance Surface Air kerma(mGy) University of Ghana http://ugspace.ug.edu.gh 10 9 8 7 6 5 y = 0.2522e0.1068x R² = 0.9984 4 3 25 27 29 31 33 35 Tube Voltage(kV) Figure 4.4: A graph of entrance surface air kerma with tube voltage of facility “C” From the results (Table 4.10) estimated mean glandular dose at different tube voltages (kV) per the ACR standard were lower than the recommended value of < 3.0 mGy (ACR) and the acceptable value of < 2.5 mGy (IAEA). Table 4.11: Results of Mean Glandular Dose (MGD) Estimation using 45 mm phantom thickness at 28 kVp and 50 mAs. Facility ESAK (mGy) Mean Glandular Dose(mGy) A 4.98±0.004 1.05 B 5.07±0.006 1.08 C 5.02±0.004 0.98 45 Entrance Surface Air kerma(mGy) University of Ghana http://ugspace.ug.edu.gh At 28 kV, the estimated mean glandular dose for facility A was 1.05 mGy, facility B was 1.08 mGy and facility C was 0.98 mGy as shown in Table 4.11. When the estimated MGD compared to IAEA (2.0 mGy) and ACR (3.0 mGy) standards, all of the recorded results were within the acceptable limits [14, 16]. The results confirmed that the facilities performing mammography procedures were operating within the recommended radiation dose levels which are suitable for patient safety. It is important that patients undergoing diagnostic or screening procedures are not overexposed whiles other factors required to ensure optimum image quality are seriously considered during an examination or procedure. Table 4.12: Comparison of estimated mean glandular dose (MGD) of selected mammography facilities at 28 kV with International Atomic Energy Commission (IAEA) and American College of Radiology (ACR) standards. Facility Mean Glandular Dose IAEA (MGD) ACR (MGD) (MGD) (mGy) (mGy)[16] (mGy)[14] A 1.05 2 3 B 1.08 2 3 C 0.98 2 3 D 2 2 3 46 University of Ghana http://ugspace.ug.edu.gh 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 A B C IAEA ACR Facility Figure 4.5: Comparison of estimated Mean Glandular Dose (MGD) of selected mammography facilities with those of International Atomic Energy Agency (IAEA) and American College of Radiology (ACR). 47 MGD(mGY) University of Ghana http://ugspace.ug.edu.gh CHAPTER FIVE CONCLUSION AND RECOMMENDATION 5.0 Overview This chapter presents the conclusion from the study and some recommendations for managements of mammography facilities and the regulatory authority. 5.1 Conclusion The analysis of information obtained from the questionnaire administered to the mammography facilities showed that they did not meet quality management system performance requirements. The deficient areas include absence of documentation of polices related to quality objectives, procedures and instructions, lack of internal and external audits, lack of appropriate education and training programms, lack of quality control programm, there is no means of patient dose assessment and absence of management committees to ensure that well documented quality management system programmes are monitored and reviewed periodically as recommended. Different tests performed to evaluate the performance of four mammography facilities that were used for the study were assessed by performing some quality control tests on them. The study showed only facility A has passed the test of. kVp. All the facility passed kVp repeatability, output linearity and repeatability. Facilities A and B recorded the highest half value layer of 0.36 mm Al and 0.37 mm Al and facility C recorded the half value of 0.34 mm Al respectively while facility D recorded least half value layer of 0.29 mm Al at 28 kV. Except for facility D all the values are within the recommended 48 University of Ghana http://ugspace.ug.edu.gh limits of greater than 0.31 mm Al. The HVL results confirm the beam qualities for facilities A, B, and C are acceptable for imaging. Image quality of the mammography equipment using the Leeds test object were within tolerance levels. The estimated value of mean glandular dose confirmed that radiation doses delivered during procedures were within the recommend Diagnostic Reference Levels (DRLs) with facilities B and C recording the highest and lowest mean glandular dose (MGD) of 1.08 mGy and 0.98 mGy respectively at a tube voltage of 28 kV for a 4.5 cm breast equivalent phantom thickness. Differences in dose levels observed could be attributed to variation in mammography equipment characteristics and imaging protocols used. 5.2 Recommendation Based on the study results and the conclusion of this research, the following recommendations are addressed to relevant stakeholders to achieve optimization of patient radiation protection in mammography practices. 5.2.1 For Management of Mammography Facilities Management of the mammography facilities should be informed about the importance of establishing an effective quality management system which must be implemented, assessed and continually improved through review and in line with the quality objectives of the facility. Management must make sure that their staff involved in radiological activities are provided with the opportunity to be involved in continuous education and training. This can help improve their proficiencies in performing procedures. 49 University of Ghana http://ugspace.ug.edu.gh Doses delivered to patients should be monitored to ensure patients are not overexposed. Patient dose monitoring should be done every six months and after any major maintenance and repair works. Management must show its commitment to the establishment, implementation, assessment and continual improvement of the management system by allocating adequate resources necessary and make them available to carry out quality management activities. Lessons learned from daily operational activities should be kept as operating experience of the facility to improve the quality of images good enough for diagnosis whiles protecting patients from overexposures. 5.2.2 For Regulatory Authority The regulatory authority must ensure that management of mammography facilities establish and implement a quality managements system. Enforce documentation of QMS (quality management system) including QA (quality assurance) and QC (quality control) information such as maintenance and repair works, policies, training programmes, patients and staff dose evaluation and any implemented corrective actions are checked during inspections. 50 University of Ghana http://ugspace.ug.edu.gh REFERENCES 1. American College of Radiology (ACR) 1999. Mammography Quality Control Manual, (ACR: Reston):467-478 2. E. Akrobortu, M. Boadu, J. Yeboah, C. Schandoff and P. K. Gyekye 2013. Inter- Comparison of Dose Indicators and Mean Glandular Dose for some Selected Diagnostic Mammography Units in Accra, Ghana. International Journal of Science and Technology 3 (5):291-295 3. J. S. Wambani 2011. Assessment of Patient Doses during Mammography Practice at Kenyatta National Hospital, Kenya. East African Medical Journal: 368-376. 4. Health and Consumer Protection Directorate General 2006. European guidelines for quality assurance in breast cancer screening and diagnosis: The European Protocol for the Quality Control of the Physical and Technical Aspects of Mammography Screening. Luxembourg: Office for Official Publications of the European Communities. 4th edn. ISBN 92-79-01258-4 (2006). 5. CA Cancer J Clin 2016. 7–30. © 2015 American Cancer Society. 6. European Nuclear Society, 2015. Tissue Weighting Factor at http://www.euronucler.org/info/encyclopedia/tissue-weighting-factor.htm 7. Dellie S.T, A. Durga Prasada Rao, Daniel Admassie and Atnatiwos Zeleke Meshesha 2012. Evaluation of Mean Glandular Dose during Diagnostic Mammography Examination for Detection of Breast Pathology in Ethiopia. OMICS Journal of Radiology.1(4):109 51 University of Ghana http://ugspace.ug.edu.gh 8. International Commission on Radiological Protection 2007. The 2007 Recommendations of the International Commission on Radiological Protection. Annals of the ICRP Publication 103. Ann.ICRP37:2-4 9. G K Korir GK, JS Wambani, IK Korir 2013, Quality management systems in radiology. SA Journal of Radiology 17(3):86-87 10. International Commission on Radiation Units and Measurement ICRU 2009. 11. Mammography, 2012, Accessed at http://www.radiologyinfo.org/en/info.cfm?pg=mammo on 2nd November. 12. Testagrossa B, Acri G, Causa F, Novario R, Tripepi M G, Vermiglio G. 2012. Unified Procedures for Quality Controls in Analogue and Digital Mammography, Chapter 14:293-313 13. Dellie et al., 2012, Evaluation of Mean Glandular Dose during Diagnostic Mammography, OMICS J Radiology. 14. International Atomic Energy Agency 2011. Quality Assurance program for digital radiography. IAEA Human Health Series International, No. 17:79-134 15. Christina Ols´en 2008. Automatic Image Analysis for Computerised Mammography. (Towards Automatic Image Analysis for Computerized Mammography. Christina Ols´en colsen@cs.umu.se, PhD Thesis, 2008. 16. International Atomic Energy Agency, 2009, Quality Assurance Program for Screen Film Mammography, IAEA Human Health Series International, No. 2:121-148 17. Perry N, Broeders M, De Wolf C, Tőrnberg S, Holland R, Von Karsa L, Puthaar E. 2006. European Guidelines for Quality Assurance in Breast Cancer Screening and Diagnosis, Fourth Edition, European Communities, Luxembourg.19(4):614-622. 52 University of Ghana http://ugspace.ug.edu.gh 18. Pacifici, S. and Radswiki , Mammography views Accessed at http://radiopaedia.org/articles/mediolateral-view on 2nd November, 2012 19. Mammography accessed at:( http://hyperphysics.phy-astr.gsu.edu/ hbase/ quantum/ xtube.html) 20. Mammography accessed at (reff: https://www.nde-ed.org) 21. Sprawls, P. 2013. Accessed at http://www.sprawls.org/ppmi2/NOISE on February 2018. 22. Bouzarjomehri, F., Mostaar, A., Ghasemi, A., Ehramposh, M.H., Khosravi, H., Physics 2006. The Study of Mean Glandular Dose in Mammography in Yazd and the Factors Affecting It. Iran Journal of Radiology, 4(1): 29-35. 23. European Communities (EC) 2006. European guidelines for quality assurance in breast cancer screening and diagnosis:57-148 24. American College of Radiology 1994. Mammography Quality Control Manual 25. International Atomic Energy Agency 2006. The Management System for Facilities and Activities, IAEA Safety Standard Series No. GS-R-S:7-9 26. American Association of Physicists in Medicine, Task Group NO. 7 1990. Diagnostic X-ray Imaging, Equipment Requirements and Quality Control for Mammography protocol on dosimetry in mammography. European Commission, Luxembourg:63-86 27. Commission of the European Communities (CEC) 1996. European AAPM Report No. 27. 28. International Commission on Radiological Protection 2007. Radiological Protection and Safety in Medicine, ICRP Publication 103. Pergamon Press, Oxford and New York (2007). 53 University of Ghana http://ugspace.ug.edu.gh 29. International Atomic Energy Agency 1996. International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources. Safety series No. 115. 30. International Commission on Radiological Protection 1996. Radiological Protection and Safety in Medicine, ICRP Publication 73. Pergamon Press, Oxford and New York (1996). 31. International Atomic Energy Agency 2005. Optimization of the radiological protection of patients undergoing radiography, fluoroscopy and computed tomography: final report of a coordinated research project in Africa, Asia and Eastern Europe. 32. International Atomic Energy Agency 2006. Applying radiation safety standards in diagnostic radiology and interventional procedures using X- rays. 33. Fabiszewska E, Grabska I, Pasicz K,Skrzynski W, Bulski W 2014. Assessment of mammography equipment quality in mammography screening facilities in 2007 and 2011 in Poland. Nowotwory. Journal of Oncology, 64:119–28. 34. Perry N, Broeders M, de Wolf C, Tornebrgs S, Holland R, Von Karsa L,Puthaar E 2013. European guidelines for quality assurance in breast cancer screening and diagnosis 4th edition. Luxembourg: Office for Official Publications of the European Union. 35. Klabunde C, Bouchard F, Taplin S, Scharpantgen A, Ballard-Barbash R. 2001. Quality assurance for screening mammography: an international comparison. J Epidemiol Community Health. 01; 55(3):204–212. 54 University of Ghana http://ugspace.ug.edu.gh 36. American College of Radiology 2018. ACR Practice Parameter for the Performance of Screening and Diagnostic Mammography (revised 2018 (Resolution 35)). APPENDICES APPENDIX A: QUESTIONNAIRE QUESTIONNAIRE FOR ASSESSMENT QUALITY MANAGEMENT SYSTEM (QMS) OF THE MAMMOGRPHY FACILITY PART I: GENERAL INFORMATION Date: ........................... Name of Facility................................................................................................................... Location................................................................................................................................. Address.................................................................................................................................. Name of officer in charge...................................................................................................... Please state your position and rank? .................................................................................... How many years have you been working with this facility/department? ........................... 1. How many mammographic machines do you have at the facility? ......................... 2. When was the machine(s) installed? ......................... 3. Was an acceptance test performed during the commissioning of the equipment? Yes [ ] No [ ] 4. What is your current staffing level as per the following category? Category Total Number of Staff Male Female Radiologist(s) Radiographer(s) Radiation Protection officer Medical Physicists Qualified Expert 55 University of Ghana http://ugspace.ug.edu.gh 5. Do you consider the above staffing level as adequate for your facility? Yes [ ] No [ ] 6. What category of mammography procedures are the facility licensed to perform? (i) Diagnostic mammography [ ] (ii) Screening mammography [ ] (iii) Both [ ] 7. What category of procedures is the facility currently performing? (i) Diagnostic mammography [ ] (ii) Screening mammography [ ] (iii) Both [ ] 8. What type(s) of medical imaging protocols does your facility perform? (i) ............................................................................... (ii) ............................................................................... (iii) ............................................................................... (iv) ............................................................................... 9. Please provide facility frequency examinations Type of examination Weekly work load Monthly work Yearly Work load load 56 University of Ghana http://ugspace.ug.edu.gh PART II: QUALITY MANAGEMENT 1. Does the facility have a document on the following? (i) Quality policy Yes [ ] No [ ] (ii) It description of the functional responsibilities, accountabilities and levels of authority. Yes [ ] No [ ] (iii) A description of the processes and supporting information that explain how work is to be carried out, reviewed, carried out, recorded, assessed and improved. Yes [ ] No [ ] 2. What measures are there to ensure confidentiality of patient-related information? .................................................................................................................................... .................................................................................................................................... Is there a policy in place to monitor, analyze and report, and periodically review procedures or activities that may have the potential to affect the smooth implementation of quality management system? Yes [ ] No [ ] 3. Does the facility/hospital ensures that personnel have access to quality management system documentation i.e. policies; procedures; instructions etc? Yes [ ] No [ ] 4. Do patients have access to quality management systems related documents? Yes [ ] No [ ] 5. Do regulatory authority‟s representatives have access to quality management systems related documents? Yes [ ] No [ ] 6. Is the management ensured the following: (i) Establish a quality policy for the facility/hospital? Yes [ ] No [ ] (ii) Establish quality objectives? Yes [ ] No [ ] 57 University of Ghana http://ugspace.ug.edu.gh (iii) Made resources available for the smooth implementation of quality management systems. Yes [ ] No [ ] (iv) Patients, statutory and regulatory requirements are fulfilled. Yes [ ] No [ ] 7. Does the facility have a quality management committee that included representatives from all departments or levels of the facility/hospital? Yes [ ] No [ ] 8. Does management review of the quality management systems to ensure the continuing suitability, adequacy and effectiveness? Yes [ ] No [ ] 9. Are records of such review kept and made available when necessary? Yes [ ] No [ ] 10. Does management make resources available to implement and maintain the system and continually improve its effectiveness as well as enhance patient‟s satisfaction by meeting patient requirement? Yes [ ] No [ ] 11. Has management ensured that appropriate communication processes are established within the facility/hospital and that communication takes place regarding the effectiveness of the quality systems? Yes [ ] No [ ] 12. Are information such as the average duration for diagnostic mammography procedure and the amount of radiation received during the procedure and information regarding the possibility of pain or discomfort made known to patients? Yes [ ] No [ ] 13. Are there arrangements for patient communication related to mammography procedures information and patient‟s complaints? Yes [ ] No [ ] 58 University of Ghana http://ugspace.ug.edu.gh 14. Does the facility/hospital plan and implement monitoring, measurement, analysis and improvement of processes and procedures? Yes [ ] No [ ] If yes, how often/frequency? …………………………………………………………………………………… 15. Does the facility/hospital have a procedure on monitoring patient‟s information as to whether patient‟s needs are fulfilled? Yes [ ] No [ ] 16. Does the facility/hospital perform internal clinical audits? Yes [ ] No [ ] 17. Is there a documented procedure that defines the responsibilities and requirements for planning and conducting internal audits, and for reporting results and maintaining records? Yes [ ] No [ ] 18. Are external auditors engaged to perform clinical audit for the facility/hospital? Yes [ ] No [ ] Does the facility/hospital continually improve the effectiveness of the quality management systems through the use of the quality policy, quality objectives, audit results, analysis of data, corrective and preventive actions and management review? Yes [ ] No [ ] III. Human Resource 19. Does the facility/hospital maintain appropriate records of education, training, skills and experience of staff? Yes [ ] No [ ] 20. Are additional and continuing training needs of staff identified by the facility/hospital and met to ensure that the quality standards are maintained and improved? Yes [ ] No [ ] 21. Are there opportunities for further education for personnel? Yes [ ] No [ ] 59 University of Ghana http://ugspace.ug.edu.gh 22. Does the facility perform/conduct annual individual Human Resource Development? Yes [ ] No [ ] IV. QUALITY CONTROL 23. Who is/are (Radiographer, medical Physicist, Engineers) responsible for conducting and documenting quality control activities and what is their educational qualification? Officer(s) Educational Qualification 24. Is there a QC (quality control) manual for the performing the various QC tests? Yes [ ] No [ ] 25. Does the quality control manual indicate the following? (i) The measuring instrument or tools to be used. Yes [ ] No [ ] (ii) The operational details? Yes [ ] No [ ] (iii) Which officer (Radiographer, Medical Physicist, and Technologist) is required to perform the tests? Yes [ ] No [ ] (iv) The qualification of person(s) required to perform the tests. Yes [ ] No[ ] (v) The recommended frequency of tests and their respective tolerance and limiting values? Yes [ ] No [ ] 26. Do you perform quality control tests at your facility and at what frequencies? TESTS YES/NO FREQUENCY 1. Reproducibility and accuracy of kVp 2. Beam Quality Assessment-HVL 3. Placement of X-ray field (image receptor 60 University of Ghana http://ugspace.ug.edu.gh and tube output) 4. X- ray film processor (sensitometry, temperature); 5. Evaluation of optical density control set of AEC(Thickness compensation, Voltage compensation, Reproducibility of AEC) 6. uniformity of film viewing boxes 7. Evaluation Image Quality 8. Evaluation of source-to image distance and focal spot size 9. Reproducibility and accuracy of kVp 27. Are patient doses monitored? Yes [ ] No [ ] If No, State reasons. ……………………………………………………………………………………… ……………………………………………………………………………………… 28. How does the facility control exposures to patients undergoing procedures? ……………………………………………………………………………………… ……………………………………………………………………………………… 29. How are patients protected from under or over exposure of patients during procedures? ……………………………………………………………………………………… ……………………………………………………………………………………. 30. When there is an overexposure to the patients, do you inform the patients? Yes [ ] No [ ]. If yes, how do you inform them? ……………………………………………………………………………………… …………………………………………………………………………………… 61 University of Ghana http://ugspace.ug.edu.gh 31. What is your choice of film types for procedures? ……………………………………………………………………………………… …………………………………………………………………………………… 32. What are the reason(s) for your choice? ……………………………………………………………………………………… …………………………………………………………………………………… 33. How are films kept at your facility? ……………………………………………………………………………………… …………………………………………………………………………………… 34. What is the type/make of equipment used in your facility? Equipment Type/Make Screen Cassette Film processor Anode material Filtration material 35. How do you ensure quality image during procedures? ……………………………………………………………………………………… …………………………………………………………………………………… 36. Is the AEC system of the mammographic equipment utilized during procedures? Yes [ ] No [ ]. If No, State reasons ……………………………………………………………………………………… …………………………………………………………………………………… 62 University of Ghana http://ugspace.ug.edu.gh 37. What AEC modes and target/filter combination are used and under what circumstances? ……………………………………………………………………………………… ……………………………………………………………………………………… APPENDIX B: DATA COLLECTION FORM APPENDIX B1: Equipment specification sheet Characteristic Results 1 Type of equipment CR DR 2 Manufacturer 3 Model 4 Year of make 5 Serial Number 6 Mode of operation 7 Anode/filter combination 8 kVp range mAs range 63 University of Ghana http://ugspace.ug.edu.gh APPENDIX B2: Mammography unit assembly assessment FACILITIES PARAMETERS A B C D Mechanical stability of free- standing unit Lights indicator Units motion function Locks and detents function Angulation indicators Wobble and vibration Image receptors sliding and holding during gantry angulation Compression paddle condition Automatic compression release Operator shielding evaluation Safety of patient/operator 64 University of Ghana http://ugspace.ug.edu.gh against units Availability of technique parameters chart APPENDIX B3: Data Sheet for Accuracy and Repeatability of the Tube Kvp Measurement Tube kVp Accuracy and repeatability kVp meter used: Meter settings: kvpnom setting Large/small( Focal spot) mA setting mAs setting Measured kvp values: Kvp1 Kvp2 Repeatability (difference (%)) Additional measurements: Kvp3 Kvp4 Kvp5 Mean kvp Standard deviation (SD) Repeatability: COV (%) Repeatability: Acceptable? Y/N Nominal kvp Accuracy (%) Tolerance Pass (Y/N) Repeatability COV (5%) Accuracy DEV (%) 65 University of Ghana http://ugspace.ug.edu.gh APPENDIX B4: Data Sheet for Half Value Layer Measurement Half-value layer Dosimetry system used Units (mGy, mR) Nominal kvp setting Focal spot (Large/small) Anode Filtration Parameter, C mA setting mAs setting Air kerma or exposure measurements: No. Aluminum filtration, Mo 0.2mm of added Al,M1 0.3mm of added Al,M2 0.4mm of added Al,M3 0.5mm of added Al,M4 0.6mm of added Al,M5 Repeat No. Aluminum filtration, Mo Average No. aluminum filtration, Mo Record thicknesses (ta < Ta tb) and air kerma or Tb exposure values that Ma bracket ko/2: (ka>kb) Mb Calculated HVL(mmAl) Tolerance 66 University of Ghana http://ugspace.ug.edu.gh Minimum Allowed HVL (mmAl) Maximum Allowed HVL (mmAl) Acceptable HVL All HVLs acceptable APPENDIX B5: Data Sheet for Output Linearity and Repeatability Test Dosimetry system used Units (mGy or mR) P(mbar) Temp(oC) To( oC) Focus size Large Anode Mo Filter Mo Nominal kvp settings 28 R1 mAs= 40 R2 R3 R4 R5 Repeatability: Difference (%) Average value Standard deviation Repeatability: COV (%) Output (Y1) mAs= 80 R1 R2 Average value Output (Y2) mAs= 120 R1 R2 Average value Output (Y3) Linearity L1 L2 67 University of Ghana http://ugspace.ug.edu.gh APPENDIX B6: Data Sheet for AEC Repeatability Test PMMA(mm) kVp(kV) mAs(mAs) Mean SD COV APPENDIX B7: Data Sheet for ESAK and MGD estimation PMMA Calibration factor kVp mAs Anode/target Filtration Dosimetery system used Operation mode Semi-Automatic/ Automatic Nominal 28 30 32 34 kVp Target/fi Mo/Mo Mo/Mo Mo/Mo Mo/Mo lter (Mo/Rh) (Mo/Rh) (Mo/Rh) (Mo/Rh) R1 68 University of Ghana http://ugspace.ug.edu.gh R2 R3 R4 R5 APPENDIX C: TABULATED CONVERSION FACTORS USED MGD CALCULATION APPENDIX C1: g and c factors HVL g factor(mGy/mGy) c factor Product of g and c (mm Al) 0.30 0.155 1.109 0.172 0.35 0.177 1.105 0.196 0.40 0.198 1.102 0.218 0.45 0.220 1.099 0.242 0.50 0.245 1.096 0.269 0.55 0.272 1.091 0.297 0.60 0.295 1.088 0.321 (16) APPENDIX C2: s factor anode–filter combinations Target filter combination s factor Target/filter combination s factor Mo/Mo 1.000 69 University of Ghana http://ugspace.ug.edu.gh Mo/Rh 1.017 Rh/Rh 1.061 Rh/Al 1.044 W/Rh 1.042 (16) APPENDIX C3: International Acceptable and achievable limits for Mean Glandular Dose (MGD) Table 21: IAEA (ACCEPTABLE AND ACHIEVABLE OF MEAN GLANDULAR DOSE) (DG) Thickness of Thickness of Acceptable level for DG Achievable level for DG PMMA equivalent breast to equivalent breast to equivalent breast (mm) (mm) (mGy) (mGy) 20 21 1.0 0.6 30 32 1.5 1.0 40 45 2.0 1.6 45 53 2.5 2.0 50 60 3.0 2.4 60 75 4.5 3.6 70 90 6.5 5.1 APPENDIX D: MAMMOGRAPHY PERFORMANCE TEST at 28kVp Quality control test Results Remarks Acceptable range A B C D Pass/fail kVp accuracy DEV(%) (± 5%) 4.19 -7.38 5.45 -53.20 Only A pass kVp repeatability COV (%) ≤ 2% 0.00 0.54 0.00 0.01 pass HVL (mmAl) 0.37 0.37 0.34 0.29 2pass (kVp/100+0.03≤HVL≤kVp/(100+c) 1Fail 70 University of Ghana http://ugspace.ug.edu.gh Output repeatability (COV (%) ≤ (5 0.77 0.03 0.32 0.36 pass %) Output linearity (L (%) < 10%) 3.12 0.69 0.44 5.55 pass AEC repeatability COV (%) ≤ 5% 0.31 1.06 0.18 - Pass Compression thickness 0.00 5.00 5.00 - Pass APPENDIX E: RESULTS OF kVp ACCURACY AND REPEATABILITY OF THE TEST Target/ Facility Filter Nom Min Max Mean Accu. Rep SD COV -4 -4 A Mo/Mo 28 26.82 26.83 26.83 4.19 4*10 3.73*10 0.02 -3 30 28.70 28.80 28.80 4.17 3.48*10 0.071 0.246 -4 -3 32 31.19 31.19 31.19 2.55 3.21*10 7.07*10 0.023 -3 B Mo/Mo 28 25.84 25.98 25.93 -7.38 5.42*10 0.081 0.312 -4 -3 30 27.83 27.84 27.84 -7.21 3.58*10 5.77*10 0.021 -4 -3 32 29.57 29.58 29.58 -7.57 3.38*10 5.77*10 0.02 -4 -3 C Mo/Mo 28 26.47 26.48 26.48 -5.45 3.78*10 7.07*10 0.027 -3 -2 30 28.35 28.38 28.37 -5.45 1.06*10 2.12*10 0.075 -4 -2 32 30.57 30.59 30.58 -4.44 6.54*10 1.41*10 0.046 D Mo/Mo 28 42.73 43.33 42.90 -53.2 0.014 0.29 0.677 -4 -2 30 47.14 47.18 47.16 -57.21 8.49*10 2.08*10 0.044 32 - - - - - - - 71 University of Ghana http://ugspace.ug.edu.gh APPENDIX F: OUTPUT LINEARITY AND REPEATABILITY OF THE ALL FACILITY LINEARITY FACILITY A B C D mAs Nom kVp 28 28 28 28 40 R1 3.396 3.542 3.474 1.955 R2 3.372 3.541 3.463 1.952 R3 3.370 3.495 3.465 1.948 R4 3.396 3.542 3.463 1.874 R5 Repeatability: 0.772 0.028 0.318 0.359 Difference (%) Average 3.379 3.542 3.467 1.932 SD 0.014 0.001 0.006 0.039 COV% 0.428 0.020 0.169 2.015 Output(Y1) 0.084 0.089 0.087 0.048 80 R1 6.973 6.817 3.745 R2 6.971 6.781 3.742 Average 6.648 6.972 6.799 3.744 Output(Y2) 0.083 0.087 0.085 0.047 72 University of Ghana http://ugspace.ug.edu.gh 125 R1 10.75 10.53 5.227 R2 10.74 10.53 5.242 Average 9.760 10.745 10.530 5.235 Output(Y3) 0.078 0.086 0.084 0.042 Linearity 3.120 0.678 0.442 5.546 APPENDIX G: HALF VALUE LAYER (HVL) OR BEAM QUALITY MEASUREMENT Table G.1 Aluminum thickness and corresponding exposure values obtained for facility A at Tube Voltage = 28 kV Tube Load = 40 mAs Aluminum Thickness (mm) Average Exposure (mGy) 0 3.371 0.2 2.251 0.3 1.881 0.4 1.587 0.5 - Table G.2 Aluminum thickness and corresponding exposure values obtained for facility B at Tube Voltage = 28 kV Tube Load = 40 mAs Aluminum Thickness (mm) Average Exposure (mGy) 0 3.391 73 University of Ghana http://ugspace.ug.edu.gh 0.2 2.284 0.3 1.881 0.4 1.608 0.5 - Table G.3 Aluminum thickness and corresponding exposure values obtained for facility C at Tube Voltage = 28 kV Tube Load = 40 mAs Aluminum Thickness (mm) Average Exposure (mGy) 0 3.477 0.2 2.306 0.3 1.912 0.4 1.1285 0.5 - Table G.4 Aluminum thickness and corresponding exposure values obtained for facility D at Tube Voltage = 28 kV Tube Load = 40 mAs Aluminum Thickness (mm) Average Exposure (mGy) 0 1.871 0.2 1.608 0.3 1.212 0.4 - 74 University of Ghana http://ugspace.ug.edu.gh 0.5 - APPENDIX H: RESULTS OF ESAK Table H: Results of ESAK (Entrance Surface Air Kerma) Tests. ESAK (Entrance Surface Air Kerma)(mGy) at different Tube Voltages (kV) Facility Exposure Target/ 28 30 32 34 Mode Filter A Manual Mo/Mo 4.94 6.12 7.77 9.42 B Manual Mo/Mo 5.04 6.2 7.63 9.06 C Manual Mo/Mo 5 6.19 7.81 9.43 D Manual Mo/Mo - - - - 75