A multicenter survey of current practices of 99mTc-methoxy-isobutyl-isonitrile (MIBI) imaging for the diagnosis of thyroid nodules: more standardization is essential

Abstract

Purpose Molecular imaging with 99mTc-methoxy-isobutyl-isonitrile (99mTc-MIBI, MIBI) has been used in the assessment of thyroid nodules (TNs) for more than two decades. Many studies showed that MIBI imaging is a suitable tool to rule-out malignancy when negative. However, relatively low specificity and accuracy have been described, thus, limiting its acceptance in clinical practice. Additionally, different technologies, protocols, and interpretation criteria are adopted accounting for heterogeneous data reported in the literature. Therefore, the present study was undertaken to assess the clinical use and methodology of MIBI imaging in patients with nodular thyroid disease in Europe. Methods A questionnaire was sent to 12 European centers of Nuclear Medicine. The questionnaire encompassed ultrasound (US) and fine-needle aspiration cytology (FNAC) procedures and their evaluation as well scintigraphy imaging indications, technical procedures, and interpretation criteria of MIBI imaging. Results The survey showed a good agreement of different centers in approaching TNs by TSH measurement, US evaluation and 99mTc-pertechnetate thyroid scintigraphy. MIBI imaging is mainly used to assess TNs with inconclusive/indeterminate cytological findings and selection of target nodule(s) for FNAC in patients with multi-nodular goiter. Technical procedures adopted in different centers are globally comparable and the recorded differences are unlikely to impact clinical results. However, as the main result of the present study, substantial differences were found in interpretation criteria adopted in different centers. Conclusions Our survey supports the urgent need of standardized interpretation criteria of thyroid MIBI imaging in order to improve its diagnostic performance and make results comparable in clinical practice.

Diagnostic Performance of 99mTc-Methoxy-Isobuty-Isonitrile (MIBI) for Risk Stratification of Hypofunctioning Thyroid Nodules: A European Multicenter Study

“…Secondly, the varying acquisition protocols used at the different study centers may influence the results of the MIBI imaging. However, most centers applied comparable protocols, as previously reported; therefore, a major impact is not very likely [ 7 ]. Thirdly, the EU-TIRADS categories were retrospectively classified according to the documented ultrasound features.…”

“…Thyroid ultrasound was performed by experienced examiners at each participating study center. Detailed information about the procedures and devices have been published [ 7 ]. All TN’s data were retrospectively classified according to EU-TIRADS by one experienced examiner (SAS): cysts or entirely spongiform TNs as well as entirely isoechoic or hyperechoic TNs without suspicious features were classified as low-risk TNs (EU-TIRADS 2 or 3, 0% and 2–4% risk of malignancy).…”

“…Detailed information about center-specific indications for FNAC have been described previously [ 7 ]. FNAC results were classified at each participating study center according to: The Bethesda system for reporting thyroid cytology (TBSRTC): class I non-diagnostic, class II benign, class III indeterminate (atypia of undetermined significance/follicular lesion of undetermined significance), class IV follicular neoplasm/suspicious for a follicular neoplasm, class V suspicious for malignancy, and class VI malignant [ 14 ].…”

“…Center-specific image acquisition parameter and administered MIBI activities have been previously reported [ 7 ]. Early MIBI images were acquired 10 min (median) and late images 60 min (median) after injection of 370 MBq (median) of the tracer.…”

“…Data have been published that demonstrated superiority of a semi-quantitative approach (washout index, WOind) [ 1 ]. However, a recently published European survey showed that various methods of visual image interpretation are still preferred by most centers [ 7 ]. These methods are characterized by comparing the MIBI uptake in the thyroid nodule (TN) to the uptake in the adjacent normal thyroid tissue or to the 99m Tc-pertechnetate uptake, respectively.…”