Tc-MIBI PINHOLE SPECT IN PRIMARY HYPERPARATHYROIDISM: COMPARISON WITH CONVENTIONAL SPECT, PLANAR SCINTIGRAPHY AND ULTRASONOGRAPHY

Purpose A pinhole collimator is routinely used to increase the resolution of scintigraphy. This prospective study was conducted to determine the interest of Tc-MIBI pinhole SPECT for the preoperative localization of parathyroid lesions in primary hyperparathyroidism. Methods All patients underwent a neck US, TcO4 and Tc-MIBI planar images, and two consecutive SPECT with a parallel (C-SPECT) and a pinhole collimator (P-SPECT). PSPECT 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 localization studies were compared with surgical, pathological and 6-month biological findings. Results Fifty-one patients cured after surgery were included. Surgery revealed 55 lesions (median weight 0.5g, 11 in ectopy). Sensitivities of US, planar imaging, C-SPECT and PSPECT were respectively 51%, 76%, 82% and 87%. Nine glands were only detected by tomography and 5 glands only by P-SPECT. Tc-MIBI/TcO4 planar scans and P-SPECT were complementary and 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. Conclusions A combination of planar Tc-MIBI/TcO4 scintigraphy and P-SPECT appears to be a highly accurate preoperative imaging procedure in primary hyperparathyroidism.