Development of a single photon emission microscope system with ∼200μm spatial resolution

Abstract

With a low-energy pinhole gamma camera, spatial resolution is primarily determined by the intrinsic spatial resolution of the imaging detector, the pinhole diameter, and the magnification ratio of the collimator. However, the pinhole diameter has traditionally been limited to around 1 mm due to manufacturing difficulties with tungsten. To overcome this limitation and enhance the spatial resolution of the pinhole gamma camera, we fabricated a pinhole with a diameter of 0.1 mm. This pinhole was then combined with a YAP(Ce) imaging detector to create an ultrahigh-resolution pinhole gamma camera. The imaging detector consisted of a 38 mm × 38 mm × 1 mm thick YAP(Ce) plate, optically coupled to a 2-inch square flat panel photomultiplier tube (FP-PMT) with a 1 mm thick light guide. The intrinsic spatial resolution of the YAP(Ce) imaging detector was approximately 1.4 mm FWHM for 60 keV gamma photons. The YAP(Ce) imaging detector was encased in a tungsten shield, and the 0.1 mm diameter pinhole collimator was positioned 100 mm from the imaging detector surface. With a magnification ratio of 10 at 10 mm from the pinhole center, the spatial resolution improved to approximately 0.2 mm (200 μm) at 10 mm from the pinhole center using the developed pinhole gamma camera. The system sensitivity was approximately 0.001%. High-resolution transmission images of various subjects were obtained. The developed ultrahigh-resolution pinhole gamma camera was named the “single-photon emission microscope.” This device will be valuable for applications requiring ultrahigh resolution in single-photon gamma or X-ray imaging.