SPECT/CT's Advantage for Preoperative Localization of Small Parathyroid Adenomas in Primary Hyperparathyroidism.

Purposes: The aims of this study were to assess the performance of Tc-sestamibi SPECT/CT, with diagnostic CT quality, compared with SPECT alone for preoperative localization of parathyroid adenomas and to assess the influence of adenoma weight on the correct adenoma lateralization with SPECT/CT and with SPECT alone.

Methods: Two hundred forty-nine consecutive patients, biochemically diagnosed with primary hyperparathyroidism, were examined with a combined SPECT/CT scanner. Subsequently, 200 patients with confirmed histopathology and biochemical cure after parathyroidectomy were included in this study (16 with multiglandular disease). For each patient, the SPECT-alone data were analyzed first. Thereafter, the CT information was added, and a new evaluation was performed with the combined data. In addition, for each patient, the diagnostic confidence with each method was graded on a scale based on the presence of different image features. The preoperative diagnostic findings were then compared with the surgical and histopathologic reports.

Results: The distribution of adenoma weights showed a peak at 210 mg, with a median at 338 mg. The sensitivity and specificity (multiglandular disease included) for correct classification of adenomas were significantly higher for SPECT/CT, 83% and 96%, respectively, than for SPECT alone, 80% and 93% (P < 0.01). Below 210 mg, the differences between SPECT/CT and SPECT alone in accurate adenoma lateralization were more prominent. Sixty-seven percent of all adenomas were graded with the highest confidence score with SPECT/CT compared with 53% with SPECT.

Conclusions: SPECT/CT yields fewer false-positive findings than SPECT alone. The advantage of SPECT/CT over SPECT alone was most apparent for correct lateralization of small adenomas (<210 mg).