Combination of dual-phase and dual-tracer SPECT/CT imaging with voxel-based subtraction in the assessment of normocalcemic primary hyperparathyroidism in patients with osteoporosis: a pilot study
Abstract
Objective: We hypothesized that parathyroid (PT) scintigraphy could be clinically valid in identifying patients, indicated for parathyroidectomy, presenting with consistently elevated PTH and normal serum calcium concentrations. Methods: The parathyroid was examined using Tc-99m-MIBI and (TcO4)-Tc-99m SPECT imaging in 75 patients with a BMD <= -2.5 T (lumbar spine, proximal femur, or distal one-third of the radius) with concomitantly elevated serum PTH concentration.
Results: After excluding patients with secondary hyperparathyroidism, PT scintigraphy indicated the presence of an adenoma in all patients (32) with elevated serum PTH and calcium concentrations. After parathyroidectomy, PT adenoma was confirmed in all surgically treated patients (29).
The predictive positive value of PT scintigraphy was 87%. PT scintigraphy indicated the presence of an adenoma in 26/34 patients with elevated serum PTH and normal calcium concentrations.
Of these patients, 12 were indicated for parathyroidectomy; PT adenoma was found in all cases. In these patients, the predictive positive value was 85%.
In 8 patients with increased PTH and normal serum calcium, scintigraphy did not reveal an enlarged PT. In these patients, serum PTH was significantly lower compared to patients with increased calcium and PTH.
Conclusion: The combined dual-phase/dual-tracer SPECT imaging method, including low-dose CT, improves the identification of pathological parathyroid glands and is therefore suitable for presurgical detection of both typical primary hyperparathyroidism and normocalcemic primary hyperparathyroidism. The method should be of value for better management of the increasing number of cases seen in subspecialty metabolic bone practices.