Whole-body scintigraphy with Tc-99(m)-MIBI, F-18-FDG and I-131 in patients with metastatic thyroid carcinoma

We assessed the relative usefulness of whole-body planar scintigraphy with Tc-99(m)-methoxyisobutyl isonitrile (Tc-99(m)-MIBI), 2-[F-18]fluoro-2-deoxy-D-glucose (F-18-FDG-RS) rectilinear scanning and with diagnostic and therapeutic doses of I-131, 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. F-18-FDG-RS and Tc-99(m)-MIBI scintigraphy provided similar results, but the tracer that allowed the detection of the highest number of metastases was Tc-99(m)-MIBI. Both Tc-99(m)-MIBI scintigraphy and F-18-FDG-RS appear to be more sensitive than I-131 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, F-18-FDG-PET was more sensitive than F-18-FDG-RS. Tc-99(m)-MIBI scintigraphy, a widely available and relatively non-expensive technique, therefore seems 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.