A New Concept of Liquid Xenon Time Projection Chamber for Medical Imaging

Liquid xenon time projection chambers offer a homogeneous detection medium with excellent intrinsic energy resolution, fast scintillation, and true three-dimensional position sensitivity, making them an attractive alternative to crystal-based detectors for positron emission tomography (PET). In this work, we present a new single-phase liquid xenon time projection chamber (TPC) concept optimized for medical imaging, employing combined scintillation and electroluminescence-based ionization readout to enable low-noise signal amplification and intrinsic depth-of-interaction measurement. We evaluate the system-level performance of this detector concept using Monte Carlo simulations based on OpenGATE and Geant4, with direct comparison to conventional LYSO-based PET systems. The study focuses on detection sensitivity, energy-based event selection efficiency, and reconstructed spatial resolution. While LYSO detectors provide higher absolute stopping efficiency due to their higher density, liquid xenon detectors exhibit improved photopeak purity as a result of superior intrinsic energy resolution, leading to enhanced rejection of scattered events. Point-source reconstruction studies demonstrate that the intrinsic three-dimensional position sensitivity of the liquid xenon TPC translates into a reconstructed spatial resolution of approximately 1~mm full width at half maximum (FWHM) at the system level, compared to approximately 4~mm for LYSO-based systems under comparable conditions. These results indicate that liquid-xenon-based PET detectors can achieve competitive or superior imaging performance, particularly for applications requiring high spatial resolution, large axial acceptance, and scalable detector geometries.