Recently, technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) has been used to image thyroid carcinoma. A prospective study was performed to compare the efficacy of99mTc-MIBI to thallium-201 (201T1) scintigraphy in patients with differentiated thyroid carcinoma. The clinical utility of all radionuclide imaging modalities, i.e.,99mTc-MIBI,201Tl, and iodine-131 Na (131I-Na), as well as serum thyroglobulin estimation, was evaluated. Thirty-four post-thyroidectomy patients (age range: 26-76 years) underwent 45 studies. Histopathologies studied included fourteen papillary, eight papillaryfollicular, ten follicular, one Hürthle cell, and one medullary carcinoma of the thyroid. Following optimal stimulation of endogenous thyroid stimulating hormone (i.e, TSH >-50 mU/ml), the patients underwent201Tl and99mTc-MIBI scintigraphy. Concomitant131I-Na scintigraphy was performed and serum thyroglobulin levels were measured. Sixteen scan sets were performed prior to131I-Na ablation therapy. Twenty-nine scan sets were performed following131I-Na ablation therapy. The presence or absence of thyroid cancer was established by clinical, biochemical, radiologic, and/or biopsy findings. There was no significant difference in sensitivity and specificity of201Tl scintigraphy versus99mTc-MIBI scintigraphy in pre- and postablation studies.131I-Na scintigraphy with determination of thyroglobulin level was sufficient in preablation studies. Among postablation patients, the addition of99mTc-MIBI or201Tl offered a higher diagnostic yield. Between the201Tl and99mTc-MIBI studies, there was a concordance of 69% in preablation and 97% among postablation patients (P=0.027). It is concluded that99mTc-MIBI is a suitable alternative to201Tl scintigraphy in thyroid carcinoma, especially following thyroidectomy and131I-Na therapy.131I-Na scintigraphy with serum thyroglobulin is adequate in both pre- and postablation patients. Among the post-131I-Na ablation patients,99mTc-MIBI or201Tl is extremely valuable for tumor localization, especially when the131I-Na whole-body scan is negative. The combination of99mTc-MIBI or201Tl scintigraphy with131I-Na and serum thyroglobulin offers the highest diagnostic yield.
All Science Journal Classification (ASJC) codes
- Radiology Nuclear Medicine and imaging