Simulation of the Expected Performance of a Seamless Scanner for Brain PET Based on Highly Pixelated CdTe Detectors

Abstract

The aim of this work is the evaluation of the design for a nonconventional PET scanner, the voxel imaging PET (VIP), based on pixelated room-temperature CdTe detectors yielding a true 3-D impact point with a density of 450 channels/cm(3), for a total 6 336 000 channels in a seamless ring shaped volume. The system is simulated and evaluated following the prescriptions of the NEMA NU 2-2001 and the NEMA NU 4-2008 standards. Results show that the excellent energy resolution of the CdTe detectors (1.6% for 511 keV photons), together with the small voxel pitch (1 × 1 × 2 mm(3)), and the crack-free ring geometry, give the design the potential to overcome the current limitations of PET scanners and to approach the intrinsic image resolution limits set by physics. The VIP is expected to reach a competitive sensitivity and a superior signal purity with respect to values commonly quoted for state-of-the-art scintillating crystal PETs. The system can provide 14 cps/kBq with a scatter fraction of 3.95% and 21 cps/kBq with a scatter fraction of 0.73% according to NEMA NU 2-2001 and NEMA NU 4-2008, respectively. The calculated NEC curve has a peak value of 122 kcps at 5.3 kBq/mL for NEMA NU 2-2001 and 908 kcps at 1.6 MBq/mL for NEMA NU 4-2008. The proposed scanner can achieve an image resolution of ~ 1 mm full-width at half-maximum in all directions. The virtually noise-free data sample leads to direct positive impact on the quality of the reconstructed images. As a consequence, high-quality high-resolution images can be obtained with significantly lower number of events compared to conventional scanners. Overall, simulation results suggest the VIP scanner can be operated either at normal dose for fast scanning and high patient throughput, or at low dose to decrease the patient radioactivity exposure. The design evaluation presented in this work is driving the development and the optimization of a fully operative prototype to prove the feasibility of the VIP concept.

A 2D <formula formulatype="inline"><tex Notation="TeX">$4\!\times\! 4$</tex></formula> Channel Readout ASIC for Pixelated CdTe Detectors for Medical Imaging Applications

“…As expected, it follows a linear decreasing dependency with the energy due to the constant peak time of the preamplifier. The measured trigger jitter does not pose a limitation on the performance of a PET [9], since a coincidence time window of 20 ns is established for normal operation of the PET ring [14].…”

Optimization, evaluation, and comparison of standard algorithms for image reconstruction with the VIP-PET

“…However, increasing the voxel density in the FOV corresponds to reducing the statistics per voxel with the effect of increasing the image noise. A pixel size of 0.25 mm is chosen to fulfill the sampling requirement for an imaging detector presented in [16]: Δr≤FWHM3 where Δ r is the chosen pixel size, FWHM is the full-width at half-maximum of the PSF of the scanner (~0.8 mm in the center of the FOV according to [2]).…”

Advances in PET/MR instrumentation and image reconstruction

“…Examples of these detectors are cadmium zinc telluride 44 and cadmium telluride. 45,46 Time of flight The use of ToF information in the reconstruction process converts the uniform probability of an event occurring somewhere within a line between detectors (line of response) to a Gaussian probability with full width at half maximum given by the time resolution between detectors. The width of the Gaussian probability is related to a reduced region in space where the annihilation takes place.…”