Comparative evaluation of 24-hour thyroid 131I uptake between γ camera-based method using medium-energy collimator and standard uptake probe-based method

The objective of the study was to make a quantitative comparison of 24-h thyroid uptake calculated by γ camera-based and thyroid uptake probe-based methods after administration of a diagnostic (131)I capsule in patients with benign thyroid disorders. The study group comprised 66 patients, of whom 26 were male (28-67 y old) and 40 female (20-65 y old). These patients had benign thyroid disorders (primarily hyperthyroidism [thyrotoxicosis]), most of whom had been referred for evaluation before radioiodine treatment. (131)I (25 μCi [925 MBq]) was administered, and 24-h thyroid uptake was calculated using a probe-based method and a camera-based method with a medium-energy parallel-hole collimator. The paired t test was used to check the variation in values obtained by these 2 methodologies. Of the 66 patients included in this study, 45 had clinical thyrotoxicosis and 21 had nonthyrotoxic multinodular goiter. In the group with thyrotoxicosis, neck uptake ranged from 40.13% to 97.1% by the probe-based method and 36.89% to 95.9% by the camera-based method. In the group with clinically nonthyrotoxic goiter, neck uptake ranged from 1.4% to 38.4% by the probe-based method and 0.6% to 34.8% by the camera-based method. Paired t testing was performed on both groups of patients, and P values were less than 0.05, showing good agreement within the 2 groups of data. The camera-based method is a good substitute for the probe-based method; though not producing identical results, the former could be used to derive useful quantitative information on thyroid function.