The Effect of Pinhole Collimator Masking: A New Consideration for Thyroid Imaging

Abstract

When pinhole thyroid scintigraphy is performed using a large field scintillation camera, what you see may not be what you think you see. Using a standard thyroid phantom and a cobalt-57 ruler-marker, we evaluated the actual field of view of a large-field camera-pinhole system. Because the design of the collimator masks the periphery of the large crystal, the actual useful field was markedly restricted to the center. This may be a potentially serious pitfall in thyroid scintigraphy since the field cut is not apparent on images. This pitfall can be avoided by always using the “zoom” feature for this pinhole imaging system.