Development of a Compact PET for integrated PET/CT/RT to Streamline and Enhance Functional/Anatomic Image-Guided Preclinical Radiation Oncology Researches

Abstract

To present latest progress in developing a compact and high-performance PET that will be inserted inside an existing CT image-guided small animal irradiator to establish an integrated PET/CT/RT for substantially expanded and improved image-guided RT research capabilities. 1) PET will consist of 12 detector panels in a multi-polygon configuration to provide ∼10 cm diameter trans-axial and ∼3.2 cm axial image field-of-view: Each panel consists of 4 detectors that closely tiled in a 2x2 matrix: Each detector consists of 15x15 array of 1x1x20 mm LYSO scintillators, with each end of the scintillator array read out by an 8x8 array of 2x2 mm Silicon Photomultiplier (SiPM) array to provide dual-scintillator-end readout for measuring depth-of-interaction (DOI); 2) PC Board of discrete components based electronics have been developed for reading/processing total 768 detector output channels (after readout channel reduction) with both positive and negative polarity signals from SiPMs’ anodes and cathodes; 3) Standard detector performance evaluation have been conducted, including energy, coincidence timing, DOI, and intrinsic detector spatial resolutions; 4) Imaging performance based on rotating detector panels is under investigation. Two full detector panels have already been assembled and placed opposite to each other on a rotating table, with a radioactive rod phantom between the panels. Coincident data will be acquired by the detector pairs at 6 different rotating angles span over 180 degrees, with 30 degrees between each consecutive detector angles. Data corrections, including attenuation, scatter and random will be applied before the image reconstruction. Expanded dual positive and negative polarity signal readout and processing electronics works well. All 900 crystals on each detector panel can be very well identified; energy, coincidence timing, and DOI are 18%-34%, ∼2.0 ns, and 2.4 – 3.7 mm, respectively. The detector intrinsic spatial resolution is < 1.0 mm. Overall, detectors have achieved expected performance. As anticipated, ongoing phantom imaging study with dual rotating detector panels, potentially along with the performance evaluation study of the assembled PET system, will be reported in the conference. We have developed PET detectors and readout/processing electronics with desired performance, and expect the ongoing system construction and imaging studies will quantify the PET capability for functional image guidance for small animal radiotherapy research.