Usefulness of SPECT/CT in Parathyroid Lesion Detection in Patients with Thyroid Parenchymal 99mTc-Sestamibi Retention

Abstract

Purpose Parathyroid adenoma detection with dual-phase 99m Tc-sestamibi (MIBI) scintigraphy depends on differential MIBI washout from thyroid. However, autoimmune thyroid disease (AITD) may cause MIBI to be retained in the thyroid gland and reduce parathyroid detection. We evaluated the impact of AITD on MIBI thyroid retention and additional benefit of SPECT/CT in these patients. Methods Dual phase planar MIBI and SPECT/CT was performed on 82 patients. SPECT/CT was performed immediately after delayed planar scan. Thyroid density (Hounsfield unit, CT-HU) and size were measured on CT component of SPECT/CT. MIBI uptake in early scans and retention in delayed scans were visually graded and correlated with clinical factors and CT findings. Finally, planar and SPECT/CT findings were compared for parathyroid lesion visualization according to thyroid MIBI retention. Results In early scan, multivariate analysis showed only thyroid size predicted early uptake. In delayed scan, multivariate analysis showed higher visual grade in early scan, lower CT-HU or AITD were significant predictors for delayed thyroid parenchymal retention. Overall, ten more parathyroid lesions were visualized on SPECT/CT compared to planar scans (57 vs. 47, p = 0.002). SPECT/CT was especially more useful in patients with thyroidal MIBI retention, as eight out of the ten additional lesions detected were found in patients with thyroid MIBI retention. Conclusion AITD is an important factor for MIBI thyroid parenchymal retention on delayed scans, and may impede parathyroid lesion detection. Patients with MIBI retention in the thyroid parenchyma on delayed scans are likely to benefit from an additional SPECT/CT.

Diagnostic accuracy of planar, SPECT, and SPECT/CT parathyroid scintigraphy protocols in patients with hyperparathyroidism

“…This could be because patients who underwent DTDP imaging were patients who initially underwent DT imaging and findings from the initial Tc-99m sestamibi and Tc-99m pertechnetate images were deemed insufficient for diagnosis by the nuclear medicine physician on duty thus prompting further delayed imaging, so patients in the DTDP group represented 'difficult' patients which findings were likely to be inconclusive to begin with. Both add-on SPECT and SPECT/CT improved the diagnostic accuracy over planar imaging alone which concurs with previous studies [5,[16][17][18][19]28]. However, SPECT imaging appeared to have a higher diagnostic accuracy than SPECT/CT which is unexpected and contradicts a previous study which demonstrated the superiority of SPECT/CT over SPECT alone [29].…”

Discordant findings on preoperative imaging for primary hyperparathyroidism and thyroid disease: Choosing the path to follow

“…Previous literature has demonstrated that the interpretation of parathyroid imaging is more difficult in the setting of autoimmune thyroiditis. 6,9,20 Hwang et al demonstrated increased MIBI retention in the setting of autoimmune thyroid disease. 9 Increased retention of MIBI may lead to impaired detection of abnormal parathyroid tissue and account for the decreased performance of MIBIþP in patients with thyroiditis.…”

“…6,9,20 Hwang et al demonstrated increased MIBI retention in the setting of autoimmune thyroid disease. 9 Increased retention of MIBI may lead to impaired detection of abnormal parathyroid tissue and account for the decreased performance of MIBIþP in patients with thyroiditis. Although we did not examine other imaging modalities in the present study, the utility of other imaging modalities such as 4D-CT in the setting of thyroid disease may also be altered.…”

99mTcO4-/99mTc-MIBI dual-tracer scintigraphy for preoperative localization of parathyroid adenomas

“…The main factor limiting the specificity of dual-tracer imaging is the presence of an underlying thyroid disease, such as Hashimoto’s thyroid disease or multinodular goiter. 22,23 However, some true-positive patients also had evidence of underlying thyroid disease, and both thyroid and parathyroid diseases were found in the pathological assessments of these cases. Moreover, our study suggested that dual-tracer SPECT/CT imaging could significantly reduce the impact of underlying thyroid disease on the diagnostic performance.…”