1 mm<sup>3</sup> resolution breast-dedicated PET system

We are developing a 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> resolution breast-dedicated Positron Emission Tomography (PET) system in an effort to increase the role of PET in earlier stages of breast cancer management. The system consists of two 16 cm × 9 cm × 2 cm detector panels constructed using stacked layers of 8×8 arrays of 1 mm3 LSO scintillation crystals coupled to Position Sensitive Avalanche Photodiodes (PSAPDs). Preliminary detector characterization indicates that analog multiplexed PSAPD signals coupled to ASIC readout electronics are able to resolve the 8×8 arrays of LSO crystals with an average peak-to-valley ratio of about 14, an energy resolution of 14.4% ± 0.8% at FWHM for the 511 keV photo-peak, and a paired coincidence photon time resolution of 7.3 ± 0.2 ns FWHM using the ASIC (5.2 ± 0.1 ns FHWM unpaired photon time resolution). Each 1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area PSAPD chip under bias generates 2 to 4 mW of power, and thus thermal regulation is required. A finite volume simulation of the detectors with thermal regulation features incorporated in the panels indicates that the maximum temperature variation across the thermally regulated imaging head is 4 degrees Celsius.