Limited-angle TOF-PET for intraoperative surgical applications: a simulation study

<ns3:p>Objectives: We present simulation results of a limited-angle TOF-PET system designed for intraoperative surgical applications. The purpose of this study is to show effects of various detector parameters on the resolution of reconstructed images. Methods: All simulated system configurations, and parameters were performed in GATE Monte Carlo package. In our simulation setup, detector modules typically used in whole-body PET imaging were arranged in two parallel planes: one positioned above the patient's body and the other beneath the patient/surgery bed. We simulated a phantom consisting of a cold sphere with a diameter of 15 mm and four hot sphere regions with sphere diameters of 8 mm, 6 mm, 4 mm, and 2 mm. Several parameters are simulated, including depth-of-interaction (DOI), full width at half maximum (FWHM) of the coincidence time resolution (CTR), crystal thickness, pixel size, uptake ratio and background water depth. To assess image resolution, we employed Simple Back Projection (SBP) reconstruction due to its fast speed compared to list-mode Maximum Likelihood Expectation Maximization (MLEM). We evaluated the quality of the reconstructed images using contrast-to-noise ratio (CNR), contrast recovery coefficient (CRC), and signal-to-noise ratio (SNR) metrics. The data acquisition length was set to 1 minute. Results and conclusions: Different parameters are simulated and impacts on the reconstructed image resolution are evaluated. Using detectors with 100 ps CTR, it is possible to detect 4 mm spheres with a 12 cm thickness of warm background, even with a low uptake ratio (5:1). Additionally, in the same thickness, 2 mm spheres with a larger uptake ratio (10:1) can be resolved with a 50 ps CTR. Our results indicate that with 1 minute acquisition and high timing resolution, use of intraoperative imaging with high resolution is achievable.</ns3:p>