Dual-tracer radionuclide imaging in hyperparathyroidism: thallium-201 parathyroid scintigraphy revisited

Tc-sestamibi is the current radiopharmaceutical of choice for the localization of hyperactive lesions of the parathyroid glands in patients with hyperparathyroidism. However, there are multiple factors that adversely affect the accumulation and retention Tc-sestamibi in the hyperfunctioning parathyroid tissue, resulting in a false-negative scan. The objective of this study was to investigate the possibility of an incremental diagnostic role of thallium-201 parathyroid scintigraphy in patients with presumably false-negative Tc-sestamibi scan results.

The study comprised of 22 patients including 16 with primary hyperparathyroidism (PHPT) and 6 with secondary hyperparathyroidism where Tc-sestambi scan was initially negative, inconclusive or where additional lesions were suspected on the single-photon computed tomography/computed tomography (SPECT/CT) scan with the CT component identifying lesion(s) without significant Tc-sestamibi uptake.

The results of our study show that in 22 patients (5 male, 17 female; age range 26-81; median age 53.4) further imaging with thallium-201 SPECT/CT scan showed 46.5% additional lesions in patients with hyperparathyroidism caused by an adenomatous or hyperplastic parathyroid lesion. In patients with PHPT caused by an adenomatous or hyperplastic parathyroid lesion, further imaging with thallium-201 showed 59% additional hyperactive parathyroid lesions. In patients with secondary hyperparathyroidism, further imaging with thallium-201 SPECT/CT showed additional 33.3% hyperplastic parathyroid lesions.

The results of this pilot study strongly advocate a role for thallium parathyroid SPECT/CT imaging in patients with primary and secondary hyperparathyroidism where the initial Tc-sestamibi scan is deemed to be false-negative in the presence of biochemical hyperparathyroidism.