Impact of PET crystal surface treatment and calibration method on DOI positioning accuracy: A simulation study

Dual-ended readout detector is a promising approach to extract DOI information in PET detector. To guide DOI detector design, a typical dual-ended readout DOI detector module was simulated using GATE. Four different crystal surface treatments including diffuse crystal surface combined with diffuse reflecting films (DD), diffuse crystal surface combined with specular reflecting films (DS), specular crystal surface combined with diffuse reflecting films (SD) and specular crystal surface combined with specular reflecting films (SS) was evaluated, and two different DOI calibration methods, a linear calibration method and logarithm calibration method to extract DOI positions from the simulation data were investigated. DOI calibration error and DOI resolution were calculated. Signal amplitude uniformity (SAU) was defined and calculated to evaluate the non-uniform effect of total output signal at different DOI positions under different crystal surface treatments. The results show that a DOI resolution superior to 2 mm is achievable with DD, DS and SD using either of the calibration method and a very poor DOI resolution is observed with SS. The logarithm calibration method works much better in term of reducing DOI calibration error, and the achieved DOI resolution is comparable with that using linear calibration method. The best SAU is achieved with SS while degradations in SAU are observed with DD, DS and SD. In general, a diffuse crystal surface or reflecting film leads to an improved DOI resolution but a degraded SAU. The degraded SAU will in turn deteriorate DOI resolution as well as other detector performance such as energy resolution as the reduced system SNR (signal-to-noise ratio). This work studies the impact of PET crystal surface treatment and calibration method on DOI positioning accuracy. It can provide guidance in optimizing crystal surface treatments and DOI extraction methods to facilitate dual-ended readout DOI detector design.