Administered activity optimization in skeletal scanning using MDP labeled 99Tcm

RESUMO

The objective of this study was to determine the minimum activity of the MDP labeled 99Tcm which is able to produce both, good image quality in the gamma camera and better radiological protection for the patient. Four samples of 18 patients were taken. A different protocol was applied to each sample. Each sample was divided into 3 groups of 6 patients each. The activity applied to each group was 293 MBq, 430 MBq and 598 MBq. Each study had 5 images to be assessed by expert criterion Left Side Skull, Fore Thorax, Dorsal-cervix Column, Dorsal-lumbar Column and Rear Pelvis. The Number and Rate of Counts, the Signal/Background (S/B) ratio and the patient's sizes were taken as variables for analysis. S/B ratio was the only parameter able to construct a discriminant function of the image quality. Significant difference between the image quality with 598 MBq and 430 MBq (p=0,03) were not detected. The value of 430 MBq is enough to achieve good image quality with Protocol 4 for all the images except for the skull