Evaluation of Usefulness of Radio-iodine SPECT/CT in Differentiated Thyroid Cancer

Lee, Jeong Won; Lee, Ho Young; Oh, So Won; Kim, Seok Ki; Jeong, Ki Wook; Kim, Seon Wook; Kang, Keon Wook

Abstract

PURPOSE: Localizing and differentiating a metastatic lesion of differentiated thyroid cancer (DTC) by using radio?iodine whole body scan could be difficult because a whole body scan (WBS) lacks anatomic information. This study was performed to evaluate the usefulness of radio-iodine SPECT/CT for differentiating equivocal lesions.
MATERIALS AND METHODS
Among 253 patients with DTC who had undergone radio-iodine scan between February and July 2006, 26 patients were enrolled (M:F = 8:18, Age 50.7 +/- 12.5 years) in this study. The patients had abnormal uptakes in the WBSs that necessitated precise anatomical localization for differentiating between a metastatic lesion and a false-positive lesion. SPECT/CT was performed for the region with abnormal uptake in the WBS. WBS and SPECT/CT were evaluated visually. Metastases were diagnosed based on the results of the radio-iodine scan along with the results of other radiological examinations and serological tests.
RESULTS
Based on the WBS images, 13 were suspected with cervical lymph node (LN) metastases in 16 patients with abnormal neck uptake, and in the 11 patients with abnormal extra-cervical uptakes, extra-cervical metastases were doubtful in all. After SPECT/CT was performed, the diagnostic results were altered for 16 patients (62%). SPECT/CT revealed that only 5 patients had cervical LN metastases, while 3 patients had extra-cervical (mediastinal) LN metastases. Overall, there was a 58% (15/26) change in diagnoses and plans for treatment due to SPECT/CT. Among 8 patients suspected with metastases on SPECT/CT, 6 patients underwent another radio-iodine therapy. In 96% (24/25) of the patients, the results of SPECT/CT corresponded with those of further radiological examinations and with other clinical information.
CONCLUSION
Radio-iodine SPECT/CT images permitted the differentiation of abnormal radio-iodine uptake and improved anatomical interpretation in DTC.