Effect of shielding the radioactivity outside the field of view on image quality in a dual head coincidence

Limited count rate ability and open geometry make the image duality obtaine d from dual head cameras very sensitive to radioactivity outside the camera field of view. The spatial distribution of non true events, scatter and ra ndoms, originating from radioactivity outside the FOV was investigated. The image quality quantified with the noise equivalent count rate, improved by up to 58% as a consequence of shielding. Radioactivity in the first 10 cm outside the FOV was found to contribute most significantly to the detected events. A modular and easily movable patient body shield was designed.