Design considerations for a limited-angle, dedicated breast, TOF PET scanner

Development of partial ring, dedicated breast PET scanners is an active area of research. Due to the limited angular coverage, generation of distortion and artifact free, fully 3D tomographic images is not possible without rotation of the detectors. With TOF information it is possible to achieve the 3D tomographic images with limited angular coverage and without detector rotation. We performed simulations for a breast scanner design with a ring diameter and axial length of 15-cm and comprising of a Full (180 degree in-plane angular coverage), 2/3 (120 degree in-plane angular coverage), or 1/2 (90 degree in-plane angular coverage) ring detector. Our results show that as the angular coverage decreases, improved timing resolution is needed to achieve distortion and artifact-free images. The CRC value for small hot lesions is similar in these situations to a Full ring Non-TOF scanner. Our results indicate that for this geometry a timing resolution of 600 ps or better is needed for a 2/3 ring scanner, while a timing resolution of 300 ps or better is needed for a 1/2 ring scanner. The hot lesion SNR values are similar to the expected sensitivity improvement arising from TOF reconstruction and the loss in sensitivity due to reduced geometric sensitivity in a limited angle coverage PET scanner. In particular, it is possible to maintain similar SNR characteristic in a 2/3 ring scanner with a timing resolution of 300 ps as in a full ring Non-TOF scanner.