Advantages of Pinhole Collimator Double-Phase Scintigraphy With 99mTc-MIBI in Secondary Hyperparathyroidism

Purpose: The aim of the study was to determine if pinhole collimator-acquired images can improve the detection of hyperfunctioning parathyroid glands in patients with secondary hyperparathyroidism. Methods: Forty-two patients being treated with cinacalcet for secondary hyperparathyroidism were studied prospectively. Patients were divided into 2 groups according to their levels of parathyroid hormone (PTH), the hormone that defines response to treatment: "responders'' (PTH <300 pg/mL) and "nonresponders'' (PTH >= 300 pg/mL). Double-phase scintigraphy using 888 MBq of Tc-99m-MIBI was used to acquire early and late parallel-hole and pinhole collimator images. Neck ultrasonography was performed on all patients to identify intrathyroid nodules. All focal uptake in any of the acquired scintigraphic images was considered positive. Results: The responder group included 24 patients, whereas 18 patients were considered as nonresponders. At least 1 parathyroid gland with Tc-99m-MIBI uptake was detected in 33 of 42 patients, with a total of 50 parathyroid glands located. We found significant differences between the detection rates of late pinhole collimator and the late parallel-hole images (74% vs 48%, P = 0.0036). This detection rate was highest with late parallel-hole images in the nonresponder group (89%). Conclusions: The late pinhole collimator acquisition showed the highest detection rate of hyperfunctioning parathyroid glands using Tc-99m-MIBI scintigraphy in secondary hyperparathyroidism patients treated with cinacalcet.