maxPET: A dedicated mammary and axillary region PET imaging system for breast cancer

In this paper, we present initial measurements from a high-performance prototype dedicated PET camera (maxPET) designed for mammary and axillary region imaging. The system consists of two 15 x 15 cm(2) planar scintillation detector plates operating in coincidence, with each plate composed of 25 modular detectors. The modular detectors are comprised of a 9 x 9 array of 3 x 3 x 20 mm(3) lutetium oxyorthosilicate (LSO) detector elements, read out by a position-sensitive photomultiplier tube (PS-PMT). A multiplexing readout scheme is used to reduce the number of readout channels from 200 (4X and 4Y readouts per PS-PMT) to 8 channels per plate. The detectors have a measured intrinsic spatial resolution of 2.3 mm. Over 95% of the 4050 crystals in the system can be identified in flood histograms of the detector plates. The coincidence timing resolution for the entire system is 8.1 ns. A line source phantom was scanned with the system and images reconstructed using focal plane tomography. The estimated resolution in projection images is 4 mm based on profiles taken through the line source phantom images. The goal of the maxPET system will be to aid in breast cancer patient management by assisting in imaging women with dense fibro-glandular breasts, detecting axillary lymph node metastases without surgery, and monitoring chemotherapy effectiveness. Future research on the maxPET system will focus on changes to the electronics to improve count rate performance and timing resolution and the mounting of the detectors on a rotating gantry for tomographic studies.