  The imaging performance of a high-resolution preclinical microPET system
employing liquid xenon as the gamma ray detection medium was simulated. The
arrangement comprises a ring of detectors consisting of trapezoidal LXe time
projection ionization chambers and two arrays of large area avalanche
photodiodes for the measurement of ionization charge and scintillation light. A
key feature of the LXePET system is the ability to identify individual photon
interactions with high energy resolution and high spatial resolution in 3
dimensions and determine the correct interaction sequence using Compton
reconstruction algorithms. The simulated LXePET imaging performance was
evaluated by computing the noise equivalent count rate, the sensitivity and
point spread function for a point source, and by examining the image quality
using a micro-Derenzo phantom according to the NEMA-NU4 standard. Results of
these simulation studies included NECR peaking at 1326 kcps at 188 MBq (705
kcps at 184 MBq) for an energy window of 450 - 600 keV and a coincidence window
of 1 ns for mouse (rat) phantoms. The absolute sensitivity at the center of the
field of view was 12.6%. Radial, tangential, and axial resolutions of 22Na
point sources reconstructed with a list-mode maximum likelihood expectation
maximization algorithm were <= 0.8 mm (FWHM) throughout the field of view.
Hot-rod inserts of < 0.8 mm diameter were resolvable in the transaxial image of
a micro-Derenzo phantom. The simulations show that a liquid xenon system would
provide new capabilities for significantly enhancing PET images.
