99mTc-MIBI pinhole SPECT in primary hyperparathyroidism: comparison with conventional SPECT, planar scintigraphy and ultrasonography

Abstract

A pinhole collimator is routinely used to increase the resolution of scintigraphy. This prospective study was conducted to determine the interest of (99m)Tc-MIBI pinhole single-photon emission computed tomography (SPECT) for the preoperative localisation of parathyroid lesions in primary hyperparathyroidism. All patients underwent a neck ultrasonography (US), (99m)TcO4- and (99m)Tc-MIBI planar images and two consecutive SPECT with a parallel (C-SPECT) and a pinhole collimator (P-SPECT). P-SPECT was performed with a tilted detector equipped with a pinhole collimator and reconstructed with a dedicated OSEM algorithm. A diagnostic confidence score (CS) was assigned to each procedure considering intensity and extra-thyroidal location of suspected lesions: 0 = negative, 1 = doubtful, 2 = moderately positive, 3 = positive. The results of these preoperative localisation studies were compared with surgical, pathological and 6-month biological findings. Fifty-one patients cured after surgery were included. Surgery revealed 55 lesions (median weight 0.5 g, 11 in ectopy). Sensitivities of US, planar imaging, C-SPECT and P-SPECT were, respectively, 51, 76, 82 and 87%. Nine glands were only detected by tomography and five glands only by P-SPECT. 99mTc-MIBI/99mTcO4- planar scans and P-SPECT were complementary and, when combined together, showed the highest sensitivity (93%). Compared with planar imaging and C-SPECT, P-SPECT increased CS for 42 and 53% of lesions, respectively, and contributed to markedly reduce the number of uncertain results. A combination of planar 99mTc-MIBI/99mTcO4- scintigraphy and P-SPECT appears to be a highly accurate preoperative imaging procedure in primary hyperparathyroidism.