Correlation of technetium-99m MIBI and thallium-201 retention in solitary cold thyroid nodules with postoperative histopathology

Abstract

A comparative prospective study of technetium-99m methoxyisobutylisonitrile (MIBI) and thallium-201 with early (15 min) and delayed (90 min for MIBI, 3 h for 201Tl) imaging in the differentiation of thyroid lesions is presented. Forty patients with cold thyroid nodules visualised on 99mTc-pertechnetate scan and with dyskaryotic or atypical epithelial cells verified by fine needle aspiration biopsy underwent MIBI and 201Tl scintigraphy at 3-day intervals. Subsequent thyroidectomies were carried out in all patients. Semiquantitative analysis was performed using a lesion to non-lesion ratio on early (ER) and delayed images (DR). Additionally, a retention index (RI) was calculated using the formula RI=(DR-ER) x 100/ER. The reproducibility of the method for the early and delayed measurements was tested by analysing intra- and inter-observer variability and repeatability coefficients. Histopathologically, the nodules were found to be well-differentiated thyroid cancer in 21 patients and benign in 19 patients. There was no significant difference in the ER between malignant and benign lesions for either 201Tl or MIBI (P>0.05). However, for both agents significant differences were found between malignant and benign lesions with regard to DR (P<0.01 for 201Tl and P<0.001 for MIBI) and RI (P<0.001 for both agents). Statistical comparison of the two agents showed no significant differences (P>0.05) except with regard to DR and RI in malignant nodules (P<0.05). A receiver operating characteristic analysis was performed to determine threshold levels for the differentiation of malignant from benign nodules. Following this analysis, ER, DR and RI levels of 1.03, 1.54 and 2 for MIBI and < or =1.42, 1.24 and 5 for 201Tl were selected. Using these threshold levels, the sensitivity, specificity and accuracy of the study were 90.5%, 36.8% and 65% for ER MIBI, 61.9%, 94.7% and 77.5% for DR MIBI, 95.2%, 89.4% and 92.5% for RI MIBI, 85.7%, 47.3% and 67.5% for ER 201Tl, 80.9%, 73.6% and 77.5% for DR 201Tl, and 90.5%, 94.7% and 92.5% for RI 201Tl. In conclusion, the DR for MIBI and 201Tl is superior to the ER in detecting malignant nodules, and the RI for both MIBI and 201Tl is more valuable than the DR in differentiating malignant from benign thyroid nodules.

99mTc-MIBI Imaging in the Presurgical Characterization of Thyroid Follicular Neoplasms: Relationship to Multidrug Resistance Protein Expression

“…Our findings showed that visual and semiquantitative 99m Tc-MIBI scintiscans were not specific enough to differentiate benign oncocytic lesions from malignant ones; most oncocytic lesions, both benign and malignant, were characterized by a significantly increased uptake or retention of 99m Tc-MIBI at 2 h, in agreement with other studies (22,(25)(26)(27). Therefore, we do not advise exposing patients to 99m Tc-MIBI scintigraphy when the cytologic result is oncocytic follicular neoplasm.…”

“…Several authors have expressed the possibility that 99m Tc-MIBI scintigraphy is a reliable adjunctive procedure for improving the diagnostic accuracy of thyroid fineneedle aspiration cytology (18)(19)(20)(21)(22)(23)(24). However, the overall published data on effectiveness in differentiating thyroid cancer from benign lesions are inconclusive, mostly because of low specificity (18).…”

“…Observations that 99m Tc-MIBI scintigraphy is often positive in both benign and malignant oncocytic thyroid lesions (22,(25)(26)(27) prompted us to investigate whether its diagnostic accuracy could be increased when the nononcocytic thyroid follicular neoplasms were in advance separated (by cytologic examination) from the mitochondria-rich oncocytic ones. This study was prospectively conducted on a series of 51 cases of follicular neoplasms using both visual and semiquantitative 99m Tc-MIBI analyses.…”

“…To this purpose, some investigators have proposed thyroid 99m Tc-methoxyisobutylisonitrile ( 99m Tc-MIBI) scintiscanning in an attempt to differentiate benign from malignant thyroid nodules (18)(19)(20)(21)(22)(23)(24). Particularly, differentiated thyroid carcinoma has been reported to intensively accumulate and persistently retain 99m Tc-MIBI (18)(19)(20)(21)(22)(23)(24).…”

“…Particularly, differentiated thyroid carcinoma has been reported to intensively accumulate and persistently retain 99m Tc-MIBI (18)(19)(20)(21)(22)(23)(24). However, discrepant results have been reported about the usefulness of 99m Tc-MIBI scanning in identifying thyroid carcinoma, especially in mitochondria-rich oncocytic lesions (22,(25)(26)(27).…”