131I postterapeutic whole body scintigraphy in differentiated carcinoma of thyroid gland

The aim of the work is to evaluate the diagnostic advantages of routinely performed post-131I therapy scans in differentiated thyroid carcinoma. Post-therapy scans were obtained 3-4 days after administration of therapeutic doses of radioiodine (60-150 mCi) by a γ-camera equipped with pin whole collimator. Two hundred eighty scans were analysed - 191 were obtained in patients after ablative dose of radioiodine and 89 ones in patients with generalized disease treated with therapeutic doses. Unknown metastases were demonstrated in 35 (12.5%) POST TREATMENT SCANS. Uptake of radioiodine was seen in 7 (2.5%) metastases, which were not visualized during previous diagnostic procedures, including also diagnostic 131I whole body scans. Within 204 scans, obtained from patients after their first 131I therapy, unknown foci of uptake were demonstrated in 5.4%. Within 76 scans from patients treated with the consecutive course of 131I therapy new foci were seen in 46.6% cases. The diagnostic gain was 59.6% for bone metastases and 155 for lung metastases. Post-therapy 131I scan is a valuable diagnostic tool in differentiated thyroid carcinoma and should be performed routinely to evaluate the extent of disease. (author)