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

Abstract

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 ½ (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-free and artifact-free images with TOF. The CRC value for small hot lesions in a partial ring scanner is similar to a full ring Non-TOF scanner. Our results indicate that a timing resolution of 600ps is needed for a 2/3 ring scanner, while a timing resolution of 300ps is needed for a ½ ring scanner. We also analyzed the ratio of lesion CRC to background pixel noise (SNR) and concluded that TOF improves the SNR values of the partial ring scanner, and helps to compensate for 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 300ps as in a full ring Non-TOF scanner.