MIBI-SPECT bei kalten Knoten zur Schilddrüsenkarzinomdetektion

Abstract

The clinical usefulness of Tc-99m-MIBI in hypofunctioning thyroid nodules for detection of thyroid carcinoma is presented. Tc-99m-MIBI is a lipophilic cation and a non-specific radiopharmaceutical for tumour imaging. It has become an important imaging technique for the assessment of hypofunctioning thyroid nodules because of its high negative predictive value excluding malignant thyroid tumours. After injection of Tc-99m-MIBI either a single-phase protocol with late planar and SPECT images about 1-2 h post injection or a double-phase protocol with early (about 15-30 min p. i.) and late images (about 2 h p. i.) were reported. Findings include a reduced, an isointense or an increased Tc-99m-MIBI accumulation in the thyroid nodule in comparison to the paranodular thyroid tissue and in comparison to pertechnetate thyroid scintigraphy. A “Match” between pertechnetate and Tc-99m-MIBI scintigraphy is a concordantly decreased uptake in the thyroid nodule in comparison to the normal thyroid gland. This finding has a negative predictive value of >97% to exclude differentiated thyroid cancer. A definite “Mismatch” means a cold thyroid nodule on pertechnetate scintigraphy and an increased uptake of Tc-99m-MIBI in comparison to the MIBI-uptake of the paranodular thyroid tissue. The positive predictive value of this finding for malignancy varies between studies and is in the range of <10-65% (Cologne data: 19%) depending on the prevalence of malignant thyroid tumours in the patient population studied. An isointense uptake was not associated with thyroid malignancy according to “Cologne” data. Further studies are desirable for better characterization of the method.