Full modeling of AX-PET: a new PET device with axially oriented crystals based on Geant4 and GATE
AX-PET is a novel PET detector based on long axially arranged crystals and orthogonal Wavelength shifter
(WLS) strips, both individually readout by Geiger-mode Avalanche Photo Diodes (G-APD). Its design was
conceived in order to reduce the parallax error and simultaneously improve spatial resolution and sensitivity.
The sensitivity can be further enhanced by adding additional crystal layers as well as by including Inter-Crystal
Scatter (ICS) events, identified and processed post-acquisition. Its unique features require dedicated Monte Carlo
(MC) simulations and its non-conventional design makes modeling rather challenging. We developed an AX-PET
model based on Geant4 and GATE packages. Simulations were extensively validated against experimental data
obtained from both small scale laboratory and full module setups. The first simulations aimed at developing
an analytical model of the WLS behavior which was afterwards coupled to GATE. Full AX-PET acquisitions
were used to test the GATE simulations. The agreement between data and simulations was very good. AX-PET
simulations are employed to test and optimize image reconstruction software and, at the same time, train ICS
identification and reconstruction algorithms.