[The dependence of Tc uptake on time of acquisition, ROI and background subtraction]

Thyroid uptake of 99mTc was compared using different modes of acquisition and evaluation. The starting time of acquisition, 5 min or 20 min after injection, did not make any difference. Comparison of the rectangular standard ROl and an irregular thyroid-shaped ROl showed a slight overestimation by 0.26% for the rectangular ROl. The results demonstrate that certain differences in acquisition and evaluation of TcU are clinically not important; however, if normal values are to be defined, they have to be taken into account.