Advantages of pinhole collimator double-phase scintigraphy with 99mTc-MIBI in secondary hyperparathyroidism

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.

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 (99m)Tc-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.

The responder group included 24 patients, whereas 18 patients were considered as nonresponders. At least 1 parathyroid gland with (99m)Tc-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%).

The late pinhole collimator acquisition showed the highest detection rate of hyperfunctioning parathyroid glands using (99m)Tc-MIBI scintigraphy in secondary hyperparathyroidism patients treated with cinacalcet.