Graphical analysis ofTc thyroid scintigraphy

A new non-invasive simple method for quantitative evaluation of thyroid was presented using graphical analysis of the transfer process of technetium-99m pertechnetate (Tc) from the blood to thyroid. Thirty subjects were studied. After a bolus injection of 111 MBq ofTc, the data were recorded on a 128X128 matrix as 60 frames of 1.5-second duration. ROIs were placed over the aortic arch and bilateral thyroid lobes. The activity of the aorta was monitored instead of the arterial activity. Graphical analysis by plottingB(t)/A(t) versus {integral} 0 A( tau )d tau /A(t) gave a straight line within the first 30 seconds in all subjects. The slope of the line was the unidirectional influx rate ofTc (k u). Thyroid perfusion index (TPI) was calculated to standardize where the ratio of ROIthyroid size to ROIaorta size was set as 10.K u and TPI showed good correlation withTc thyroid uptake. Hyperthyroid patients showed high values ofk u and TPI. Considering that these indices were determined at the first pass ofTc, this method may be helpful especially in the evaluation of thyroid perfusion.