Whole-body scintigraphy with 99Tcm-MIBI, 18F-FDG and 131I in patients with metastatic thyroid carcinoma.

We assessed the relative usefulness of whole-body planar scintigraphy with 99Tcm-methoxyisobutyl isonitrile (99Tcm-MIBI), 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG-RS) rectilinear scanning and with diagnostic and therapeutic doses of 131I, for the detection of local recurrences and metastatic lesions in 12 patients with thyroid carcinoma and elevated thyroglobulin serum levels. All images were evaluated independently by three experienced observers to define the number and location of metastatic lesions. 18F-FDG-RS and 99Tcm-MIBI scintigraphy provided similar results, but the tracer that allowed the detection of the highest number of metastases was 99Tcm-MIBI. Both 99Tcm-MIBI scintigraphy and 18F-FDG-RS appear to be more sensitive than 131I scintigraphy for the detection of metastases of thyroid carcinoma. Tomographic acquisitions were also performed on a limited field of view in each subject and, as expected, 18F-FDG-PET was more sensitive than 18F-FDG-RS. 99Tcm-MIBI scintigraphy, a widely available and relatively non-expensive technique, therefore sems suitable for the assessment and follow-up of patients with metastatic thyroid carcinoma and does not require the withdrawal of hormone therapy for lesion imaging.