Dose optimization of adult head computed tomography examination in an academic hospital in Ghana

Abstract

The study investigated radiation doses and image quality of adult head CT and optimization options using an anthropomorphic RANDO phantom on the only available AquilionONE CT scanner in Ghana. Dose length product (DLP) and volume-weighted CT dose index (CTDIvol) dose descriptors were retrospectively obtained from 402 adult head CT examinations performed (from 2020 to 2021) at a Ghanaian hospital, while the effective dose (Deff) was estimated from the product of the DLP and a convention coefficient (k = 0.0023). Using the same routine head CT protocol, the anthropomorphic RANDO phantom was scanned with the hospital’s 640-slice Toshiba AquilionONE CT scanner. Subsequently, exposure factors were varied to study their effects on the dose and image quality. The adult head and phantom images were obtained in Digital Imaging and Communications in Medicine (DICOM) format, and their signal-to-noise (SNR) ratios were analyzed with ImageJ software. The facility’s mean CTDIvol, DLP, and effective dose (Deff) were 86.00 ± 0.00 mGy, 1559.68 ± 197.18 mGy cm, and 3.57 ± 0.46 mSv respectively (SNR = 7.04). For a fixed tube potential, CTDIvol, DLP, and Deff of 51.30 mGy, 1013.80 mGy cm, and 2.33 mSv were respectively achieved (SNR = 5.49) after optimization. Using automatic exposure control (AEC) in the optimization process, the respective CTDIvol, DLP and Deff values were 59.50 mGy, 1176.00 mGy cm and 2.70 mSv (SNR = 5.62). We conclude that substantial Deff reductions of 40.4% and 31.0% using a fixed tube potential, and AEC while maintaining diagnostic image quality were respectively achieved. The protocols associated with these dose-reductions are, therefore, recommended as optimization measures for head CT on the AquilionONE scanner in Ghana.