FDG-PET, I-131 and MIBI Scintigraphy in the Follow-Up of Differentiated Thyroid Cancer

Serum thyroglobulin (Tg) measurement and whole-body-scintigraphy with 131I (WBS) are widely used for detection of local recurrence, lymph node and distant metastases in the follow-up of differentiated thyroid cancer (1,2). The “myocardial tracers” thallium and 99mTc-MIBI have been proven to be useful besides 131I. 18FDG is known to be retained in malignant tissue, depending on the grade of malignancy. Some reports have been published dealing with FDG uptake in thyroid cancer, partly using a regional-body positron-emission tomography (PET) scanner and partly using a conventional gamma camera (3–6). Recently, Feine et al. (3) published first results obtained with a whole-body PET scanner. The aim of the present study was to evaluate the use of whole-body FDG-PET imaging in the follow-up of patients who have been treated with 131I and to compare the results with other imaging modalities, particularly with MIBI-scintigraphy since this radiopharmaceutical has been proven to be useful in the follow-up of (also 131I-negative) thyroid carcinomas (7).