Optimizing PET Radio-Guided Probes for Laparoscopic Surgery: Small Compton-Angles Collimation for Increased SNR and Size and Weight Reduction - Project Summary/ Abstract In the United States, approximately 60% of cancer patients undergo surgical resection. In prostate cancer surgery, the second leading cause of cancer death in men, some tumor regions are missed in 20% to 60% of cases. Employing 12 mm maximum diameter trocars, the surgical approach balances instrument accommodation and tissue damage minimization during laparoscopic procedures. While various imaging techniques help to reduce missed tumor regions, radio-guided probes face limitations with Positron Emission Tomography (TEP) prostate cancer specific tracers. Mechanical collimation effectively detects Single-photon Emission Computed Tomography (SPECT) radiotracers within the energy range of 80 keV to 300 keV, but challenges arise with higher-energy gamma rays such as the 511 keV emitted in PET. This results in bulky probes due to the dense material surrounding the detector, rendering them unsuitable for laparoscopic surgery and with poor directionality. As an alternative, detecting β+ particles instead of the 511 keV annihilation gamma rays offers a potential solution. However, this method has limited sensitivity, particularly in detecting high fixations that are not in direct contact with the probe. The aim of this project is to create a surgery probe prototype specifically designed for PET radiotracers and firstly aimed to be used during laparoscopic prostate cancer resection—adhering to the constraint of a diameter less than 12 mm. The central and novel approach is the use of two back-to-back detectors with high energy resolution, which allows the selection of small Compton angles. Selecting small Compton angles interaction means detecting only gamma rays that impinge almost from the front of detector's alignment axis. This innovative collimation method offers a remarkable improvement in signal- to-noise ratio compared to existing commercial probes, addressing limitations in laparoscopic surgery suitability. A first prototype with a bigger diameter has been developed and showed promising results compared to commercial probes with an increased signal-to-noise ratio, a weight three times lower and a reduced diameter. This first prototype will be (1) improved by using the GATE Monte Carlo simulation platform. Some different geometries and materials will be tested to find the better compromise between size and sensitivity of detectors. (2) A new prototype will be built and (3) will be compared to the commercial probes and tested by surgeons using anthropomorphic phantoms that mimic tumors in the body. Our long-term goal is to develop the world’s first laparoscopic probe for detecting 511 keV gamma rays from PET tracers that can be used in surgery routine to better identify tumors and lymph nodes by making it available to the sell market. If successful, this project will drastically ease surgeon’s procedures and will allow providing better patient’s outcomes as well as shorten the procedures, thus, reduce risks and sequels from surgery.
