Measurement of iodine-123 thyroid uptake using a gamma camera with LEAP collimator.

OBJECTIVE This study compared the 123I thyroid uptake measurements obtained from a gamma camera fitted with a low-energy all-purpose (LEAP) collimator to those obtained from a thyroid uptake probe and gamma camera fitted with a pinhole (PH) collimator. METHODS Thirty-one patients (27 female and 4 male patients) were studied for comparison between a probe and a gamma camera fitted with LEAP collimators. A different group of 25 patients (20 female and 5 male patients) were studied for comparison between LEAP and PH collimators. The patients were given 7.4-11 MBq (200-300 pCi) 123I capsules orally. Uptake with both the probe and the gamma camera was measured at 5 h and 24 h. The uptake measurements by these 3 methods were compared. RESULTS Comparison of all the camera uptake values with the probe system correlated well with correlation coefficient values ranging from 0.912-0.988. The probe system yielded uptake ratios slightly higher than those measured by the gamma camera with LEAP collimator. Comparison between LEAP and PH uptake values resulted in a correlation coefficient of 0.979 for 5 h and 0.931 for 24 h uptake. CONCLUSION Iodine-123 uptake with a gamma camera fitted with a LEAP collimator can accurately and consistantly be used to determine the thyroid uptake of 123I if proper ROIs are applied.