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 99 Tc m -methoxyisobutyl isonitrile ( 99 Tc m -MIBI), 2-[ 28 F]fluoro-2-deoxy-D-glucose ( 18 F-FDG-RS) rectilinear scanning and with diagnostic and therapeutic doses of 131 I, 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. 18 F-FDG-RS and 99 Tc m -MIBI scintigraphy provided similar results, but the tracer that allowed the detection of the highest number of metastases was 99 Tc m -MIBI. Both 99 Tc m -MIBI scintigraphy and 18 F-FDG-RS appear to be more sensitive than 131 I 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, 18 F-FG-PET was more sensitive than 18 F-F-RS. 99 Tc 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.