Usefulness of additional [99mTc]NaTcO4 SPECT/CT after standard combination of [99mTc]Tc-MIBI SPECT/CT and neck ultrasonography - improving the efficiency of parathyroid imaging in inconclusive cases.

BACKGROUND: The current standard method in hyperparathyroidism imaging is the combination of [99mTc]Tc-methoxyisobutylisonitrile ([99mTc]Tc-MIBI) single photon emission computed tomography/computed tomography (SPECT/CT) and neck ultrasonography (nUS). However, [99mTc]Tc-MIBI scintigraphy has certain limitations; thus, alternative imaging techniques may be beneficial. The following paper discusses the usefulness of performing an additional 99mTc-pertechnetate ([99mTc]NaTcO₄) SPECT/CT after a standard combination of [99mTc]Tc-MIBI SPECT/CT and neck ultrasonography to improve the efficiency of detecting parathyroid adenomas and/or hyperplasia in inconclusive cases.

MATERIAL AND METHODS: The authors retrospectively analyzed archived medical data of 58 patients who underwent parathyroid scintigraphy in 2022-2024. The study consists of patients, in whose cases [99mTc]Tc-MIBI SPECT/CT in combination with nUS did not provide a clear outcome. These patients underwent additional [99mTc]NaTcO4 SPECT/CT imaging. Radiotracer uptake in both studies was then compared visually.

RESULTS: Out of 58 patients included in the study, 40 (69%) had positive [99mTc]Tc-MIBI and [99mTc]NaTcO₄ SPECT/CT results, whereas 18 patients (31%) had a negative scintigraphy result. In 42 out of 58 cases, clinical verification of SPECT/CT results was obtained, based on which the sensitivity, specificity, and accuracy of the method were 83.3%.

CONCLUSIONS: This study demonstrates that additional [99mTc]NaTcO₄ SPECT/CT can be valuable in patients with inconclusive results in [99mTc]Tc-MIBI SPECT/CT (evaluated in combination with nUS), both to confirm and exclude the presence of hyperfunctioning parathyroid glands.