Differentiated thyroid carcinoma: diagnosis and dosimetry using 124I PET/CT

The recent availability of 124I, due in part to the spread of PET scanners, has opened up new possibilities for performing pre-therapeutic dosimetric studies in patients with differentiated thyroid cancer. 124I PET/CT has remarkable clinical potential: for disease staging and the ablation of thyroid remnants, but also for studying patients at high risk or with suspected local relapses and/or metastases; furthermore, it has a low stunning risk. Many clinical studies have shown the superiority of 124I PET/CT versus 131I conventional imaging, which is attributable to the possibility of combining morphological and highly specific functional imaging data, avoiding most of the known pitfalls of 131I scanning. 124I PET/CT can be used to perform dosimetry, avoiding the side effects of 131I, to tailor treatments, instead of using fixed therapeutic activities, and to evaluate mean absorbed doses both to target lesions (thereby allowing adequate therapy planning and staging) and to non-target organs such as the salivary glands. In addition, the concomitant use of 18F-FDG PET/CT allows the detection of non-iodine-avid lesions, discriminating these from simultaneously occurring iodine-positive lesions. This review analyzes clinical studies on 124I PET/CT in patients with differentiated thyroid cancer, and suggests possible future applications.