Thyroid blood flow and uptake of technetium-99m pertechnetate in Graves' disease

The aim of this study was to assess the relation of early thyroid blood flow (EBF) and technetium-99m pertechnetate ((99m)TcO(-)(4)) uptake, as an early diagnostic index in patients with Graves' disease (GD) by dynamic thyroid scintigraphy (40 frames, 3 sec/frame). Thirty patients with GD with mean age 50.0 +/- 9.0 y, range: 35.0-69.0 y, were studied. The results obtained were compared with those of 30 euthyroid individuals (EI) of mean age 46.9 +/- 12.5 y, range: 22.0-68.0 y. The parameters of (99m)TcO(-)(4) EBF and early uptake studied, derived from the background subtracted time activity curves, were as follows: a) The duration of the EBF in sec; b) The perfusion index (PI) - the ratio of counts at the beginning and at the end of the EBF; c) The uptake index 1 (UI1)- the counts ratio between the counts at the end of the EBF and at the 2nd min d) The uptake index 2 (UI2) - the counts ratio between the 1st min and the 2nd min of the uptake curve and e) Delayed (99m)TcO(-)(4) thyroid uptake (TcTU) at 20 min was also calculated as a percentage of net counts activity accumulated in the thyroid gland at 20 min. Results were as follows: a) The mean values of the duration of the EBF were shorter in GD patients (9.90 +/- 2.94 sec) than in EI (15.70 +/- 4.01 sec; P<0.0001); b) PI did not differ significantly (P>0.05); c) The mean UI1 and UI2 values of thyroid uptake of 99m TcO4- were significantly lower in GD (UI1=0.621, UI2=0.772) as compared to EI (UI1=1.106, UI2=0.947; P<0.0001 for both) and d) TcTU values were significantly higher in GD (13.6%) than in the group of EI (1.29%; P<0.0001). A good correlation was found in patients with GD between early (UI1 and UI2) and delayed TcTU (r = -0.562; P=0.010 and r = -0.459; P=0.042 respectively). Also, in patients with GD the EBF correlated poorly with UI1, UI2 and TcTU (P>0.05 for all these parameters). In conclusion, the results of this study indicate that the duration of EBF did not relate significantly to the height of TcTU values in patients with GD. On the contrary, the early uptake, indices UI1 and especially UI2 were shown to be faster in the majority of GD patients and correlated well with the TcTU. These parameters may be used as diagnostic indices for GD. Further investigation is required to support the above findings.