Assessment of The Quality and Suitability of Radiopharmaceutical Cold Kits and 99mo/99mtc Generator used at The Nuclear Medicine Unit, Korle-Bu Teaching Hospital, Accra

Abstract

The study investigated the quality and suitability of 99mTc radionuclide labelled cold kits used at the Nuclear Medicine Unit of Ghana’s Premier Korle Bu Teaching Hospital (KBTH) for diagnosis of diseases. The quality evaluation involved: (a) appraisal of four (4) imported 99Mo/99mTc generator packages to ensure compliance with United States Nuclear Regulatory Commission (USNRC) and International Atomic Energy Commission (IAEA) recommended acceptance criteria; (b) assessment of radionuclide purity (99Mo breakthrough [MoBT] or 99Mo contamination); (c) evaluation of the chemical purity (Al3+ content) of 99mTc eluate using colorimetric method; (d) suitability of fusing 99mTc eluate with human blood; (e) the radiochemical purity (RCP) of three (3) formulated radiopharmaceuticals: methylenediphosphonic acid (99mTc-MDP); diethylene triamine penta acetic acid (99mTc-DTPA); 2-methoxy isobutyl isonitrile (99mTc-MIBI); and, (f) the accuracy of the well type γ-counter and the Capintec dose calibrator, as well as the geometry dependence of the dose calibrator. The Wipe Test for radioactive material contamination showed no radiation leakage. The respective 1-meter radiation exposure measurements of 525, 415, 225 and 305 (μR/h) for the four generators used were all below the USNRC recommended value of 719.9×106 μR/h (200 mrem). Sodium pertechnetate (Na99mTcO4) eluate quality from the 99Mo/99mTc generators were high as a result of low MoBT (0.0001-0.039 μCi 99Mo/mCi 99mTc) for all elutions. The MoBT range is lower than the IAEA and US Pharmacopeia recommended MoBT of ≤ 0.15 μCi 99Mo/mCi 99mTc. Low MoBT signifies high γ-camera image quality (resolution); and absence of excess radiation from formulated radiopharmaceutical (RP). Chemical purity (Al3+ breakthrough) of ˂ 10 ppm were obtained for each of the 38 elutions from the four generators. This observation satisfies the ≤ 10 ppm recommended Al3+ leakage from the generator into the Na99mTcO4 eluate; signifying eluate of good quality and safe for formulation of radiopharmaceuticals. Interestingly, 99mTc eluates from all four generators gave a measured respective pH of 7; which is within the European Pharmacopeia recommended pH of 4-8 for 99mTc eluates, and appropriate and safe for fusing into human blood (pH 7.35-7.45). The assessed RCP for 99mTc-MDP and 99mTc-DTPA ranged 94.2-99.8% and 96.8-99.8% respectively. The estimated RCP for 99mTc-MIBI range from 92.6 to 96.8%. The RCP ranges obtained revealed the absence of unacceptable radiation in the three formulated radiopharmaceuticals.. The estimated RCPs for 99mTc-MIBI and, 99mTc-MDP in addition to 99mTc-DTPA were comparable to respective recommended RCP ≥ 94% (99mTc-MIBI) plus ≥ 95% (99m Tc-MDP and 99m Tc-DTPA) set by the IAEA, and the United States and European Pharmacopeiae. Quality testing of the Well-type γ-counter and Capintec Dose Calibrator gave reliable results. The accuracy test for both instruments revealed that calculated percentage (%) errors were within the IAEA recommended ±5% error margin. For geometry, the Capintec dose calibrator response of the 99mTc radioactive source established that 10 mL, 5 mL and 2 mL syringe volumes had Volume Correction Factors (VCF’s) within the IAEA recommended range of 0.95˂VCF˂1.05; and additionally, the plot of VCF for 15 consecutive days showed good regression coefficients [ R2 =0.8492 (10 mL syringe), R2 = 0.962 (5 mL syringe) and R2=1 (2 mL syringe)]. The 99mTc radiopharmaceuticals and cold kits were suitable for use in nuclear medicine diagnostics because all the quality assessments complied with globally accepted/recommended criteria.