A better MoUSE Trap detector

Abstract

We are developing trapezoidal slat crystal (TSC) PET detectors for use in ultra-compact, high-spatial-resolution PET systems for preclinical mouse imaging. In this work, we report on a new TSC detector design that we refer to as the Monolithic Unique Slat Element Trapezoidal (MoUSE Trap) design. This design improves upon the previous TSC concept by allowing for either decoding of thinner slats for better spatial resolution or taller slats for better detection efficiency. The key to the approach is a unique construction of the trapezoidal slat detector unit that supports practical fabrication. Two versions of the MoUSE Trap detector were evaluated. The first consisted of six slats each 8 mm tall and 40 mm long. The thickness of the slats ranged from 0.44 mm (front) to 0.64 mm (back). The second array consisted for four slats each 10 mm tall and 40-mm long. The thickness of the slats ranged from 0.71 mm to 1.11 mm. Mirror film of varying lengths was used to control light sharing within the crystal array. The MoUSE Trap arrays were coupled to a 2-by-12 array of MPPC elements. A statistics-based method was used for event positioning. Data were collected to calibrate the detector and to test its intrinsic spatial resolution, energy resolution, and DOI decoding performance. Results for the 6-slat detector were as follows. The average peak to valley ratio of the crystal map for slat decoding was better than 8. The average intrinsic spatial resolution along the long axis of the crystal was ∼1.05-mm FWHM after correcting for source size. The average energy resolution for the detector was < 14 % at 511 keV. The DOI positioning was < 3-mm FWHM. Two new trapezoidal slat crystal, PET detectors have been designed and evaluated. The main improvements of the designs are to either support decoding thinner slats (i.e., intrinsic spatial resolution) or taller slats (i.e., better detection efficiency).