Preoperative dual-phase parathyroid imaging with tc-99m-sestamibi: accuracy and reproducibility of the pinhole collimator with and without oblique images.

Background: Previously, we have found that the additional use of a pinhole collimator in parathyroid scintigraphy resulted in a decrease in the number of incorrect side localizations and an increase in reproducibility compared with that of using a parallel-hole collimator alone.

Purpose: The aim was to investigate whether the addition of anterior oblique views to parathyroid scintigraphy (PS) with a pinhole collimator could further enhance the diagnostic ability and reproducibility. The level of preoperative parathyroid hormone (PTH) as a potential predictor of the usefulness of the supplementary views was also studied.

Method And Material: Forty-seven patients with primary hyperparathyroidism (HPT) underwent dual-phase PS using a combined protocol with parallel-hole and pinhole collimators. The pinhole collimator was used in the anterior as well as right and left anterior oblique positions. Thyroid pertechnetate scans were undertaken in the same positions. Two observers assessed the images independently.

Results: By adding oblique views, the gain in correct side localization occurred in all cases but one was seen in patients with rapid washout. The level of PTH could not predict these patients. The observer agreement on correct side localizations rose significantly from 81% to 94%.

Conclusion: The addition of oblique views to the imaging protocol using the pinhole collimator for parathyroid and thyroid scintigraphy in primary HPT results in an increase in observer agreement and the number of correct side localizations in patients with rapid washout of MIBI. The preoperative level of PTH cannot, however, predict these patients.