Feasibility study of radioactivity estimation of Tc and I-labeled radiopharmaceuticals using shielded syringes.

This study investigates the feasibility of estimating the radioactivity of radiopharmaceuticals using shielded syringes. The radioactivities of Tc-MDP, Tc-HMDP, Tc-ECD, Tc-MAG, and I-IMP were measured using a dose calibrator. Correlation coefficients and regression equations were obtained from the radioactivity in the shielded and unshielded syringes. Tc-MDP was also measured for residual radioactivity after the administration. The correlation coefficients of Tc-MDP, Tc-HMDP, Tc-ECD, Tc-MAG, and I-IMP were r = 0.9998, r = 0.9997, r = 0.9999, r = 0.9998, and r = 0.9888, respectively. The regression equations were y = 0.0364x + 0.0913, y = 0.0349x + 0.0273, y = 0.0343x - 0.0018, y = 0.0522x + 0.1215, and y = 0.0383x + 0.0058, respectively. The correlation coefficient for the residual radioactivity of Tc-MDP was r = 0.9887 and the regression equation was y = 0.1505x + 0.0853. The radioactivity of Tc- and I-labeled radiopharmaceuticals in shielded syringes was accurately measured. It was suggested that the measuring shielded syringes could provide an estimate of the actual radioactivity.