Preoperative 123I/99mTc-Sestamibi Subtraction SPECT and SPECT/CT in Primary Hyperparathyroidism

The trend toward focused surgical parathyroidectomy requires precise preoperative localization of parathyroid lesions in patients with hyperparathyroidism. The purpose of this study was to directly compare the diagnostic accuracy of (99m)Tc-sestamibi/(123)I subtraction SPECT with SPECT/CT for the localization of abnormal parathyroid glands in patients with primary hyperparathyroidism. A total of 61 consecutive surgical patients with primary hyperparathyroidism underwent both (123)I/(99m)Tc-sestamibi subtraction SPECT and SPECT/CT scans preoperatively, using a hybrid SPECT/CT instrument that combined a dual-detector SPECT camera with a 6-slice multidetector spiral CT scanner. Four hours after being given (123)I-sodium iodide orally, each patient received (99m)Tc-sestamibi intravenously, followed immediately by a simultaneous, dual-isotope SPECT scan of the neck and upper chest. Then, without moving the patient, we performed a non-contrast-enhanced CT scan of the same body region. Normalization and subtraction of the (123)I SPECT images from the (99m)Tc SPECT images were performed. The subtraction SPECT and the coregistered fused SPECT/CT studies were interpreted separately, with images scored on a 5-point scale. Surgical and histopathologic findings were used as the standard of comparison. Surgery was successful in 57 patients (solitary parathyroid adenoma in 48 patients, double parathyroid adenomas in 6 patients, and 10 hyperplastic parathyroid glands in 3 patients). The sensitivities of SPECT (50/70 = 71%) and SPECT/CT (49/70 = 70%) were similar (P = 0.779). The specificity of SPECT/CT (26/27 = 96%) was significantly greater than that of SPECT (13/27 = 48%; P = 0.006). The receiver-operating-characteristic area under the curve of SPECT/CT (0.833) was significantly greater than that of SPECT (0.632; P < 0.001). SPECT/CT is significantly more specific than dual-isotope subtraction SPECT for the preoperative identification of parathyroid lesions in patients with primary hyperparathyroidism.