Assessment of 24-hour thyroid uptake of I-131 sodium iodide using a 5-minute uptake of technetium-99m pertechnetate

Objectives This study is aimed to investigate the thyroid uptake of patients with hyperthyroidism using two different radio nuclides [sodium iodide (¹³¹I) and technetium 99m pertechnetate (^99mTc)] and, develop a method to estimate the 24-hour ¹³¹I thyroid uptake based on a 5-minute ^99mTc thyroid uptake

Methods Ninety-nine patients with hyperthyroidism were investigated. Thirty-four patients were female, and sixty-five were male. First, ^99mTc uptake (TcU) and thyroid scintigraphy were performed using the gamma camera (GC). 24-hour iodide uptake (IU) values were determined using uptake probe (UP), two days after the initial GC study.

Results Mean age for the patients was 50 ± 16.4. Fifty percent of all patients had Grave’s disease (GD), 28 (28.3%) had toxic adenoma (TA), and 21 (21.2%) had toxic multi-nodular goiter (TMG). Mean TcU was found 7.15 ± 7.79. The IU values at 24 hours were 45.93 ± 15.4. The TcU, IU at 24 hours was higher in GD patients when compared to TA and TMG patients. TcU and 24-hour IU values demonstrated a strong logarithmical correlation (r= 0.61, p= 0.001). The formula used for estimation of IU was: y= 12.85Ln (x) + 26.07; where x represents TcU, and y represents IU at 24 hours.

Conclusions TcU values can be easily be transformed to IU values, using the above mentioned formulas and these transformed values then used to calculate ¹³¹I treatment dose for patients with hyperthyroidism where speed and minimizing radiation dose are factors.