The value of 99mTc-sestamibi SPECT/CT over conventional SPECT in the evaluation of parathyroid adenomas or hyperplasia

Abstract

As SPECT/CT technology evolves, its applications and indications need to be evaluated clinically for more efficient and cost-effective use. This retrospective study evaluated the clinical value of simultaneously acquired (99m)Tc-sestamibi SPECT/CT versus conventional SPECT in diagnosing and locating parathyroid adenomas or hyperplasia in patients with primary hyperparathyroidism.

Methods: Immediately and 60 minutes after intravenous administration of 740-925 MBq of (99m)Tc-sestamibi, static planar images of the neck and chest were obtained. SPECT/CT images were acquired 30 minutes after injection. Two experienced masked readers independently evaluated whether conventional SPECT images provided information beyond what was available from the planar images either by changing the diagnosis or by better locating the glands and whether the SPECT/CT images provided information beyond what was available from the planar plus conventional SPECT images. Forty-eight consecutive patients with a clinical diagnosis of primary hyperparathyroidism were included in the study. The 32 whose scans showed positive results underwent surgical resection and were examined histopathologically.

Results: Planar and SPECT imaging, with or without CT fusion, identified 89% of the surgically confirmed diseased parathyroid glands. Use of SPECT/CT changed the diagnosis in only 1 patient (2%) from positive to negative and better located the glands in only 4 patients (8%). SPECT/CT was particularly helpful in locating the 2 ectopic parathyroid adenomas diagnosed in this cohort. Tracer retention in diseased glands did not correlate with histologic characteristics. Also, biochemical markers did not correlate with the scan findings.

Conclusion: SPECT/CT has no significant clinical value additional to that of conventional SPECT for parathyroid imaging except in locating ectopic parathyroid glands. Eliminating the CT acquisition will spare patients the additional time, radiation exposure, and expense.