Recognizing Pinhole Parallax Error for Accurate Localization of Thyroid and Parathyroid Disease.

Parallax error is a pitfall of pinhole scintigraphy that causes mislocalization of the findings. It is important to notice this error on pinhole thyroid and parathyroid scintigraphy and obtain additional images with a parallel-hole collimator to accurately determine the upper and lower margins of large goiters and nodules and the location of ectopic thyroid tissue and parathyroid adenomas. In this teaching case report, we revisit pinhole parallax error, present pinhole and SPECT/CT images of a patient with a large, hyperactive thyroid nodule, and review the literature and potential solutions to this important problem.