Image quality assessment of LaBr₃-based whole-body 3D PET scanners: a Monte Carlo evaluation

Abstract

The main thrust for this work is the investigation and design of a whole-body PET scanner based on new lanthanum bromide scintillators. We use Monte Carlo simulations to generate data for a 3D PET scanner based on LaBr3 detectors, and to assess the count-rate capability and the reconstructed image quality of phantoms with hot and cold spheres using contrast and noise parameters. Previously we have shown that LaBr3 has very high light output, excellent energy resolution and fast timing properties which can lead to the design of a time-of-flight (TOF) whole-body PET camera. The data presented here illustrate the performance of LaBr3 without the additional benefit of TOF information, although our intention is to develop a scanner with TOF measurement capability. The only drawbacks of LaBr3 are the lower stopping power and photo-fraction which affect both sensitivity and spatial resolution. However, in 3D PET imaging where energy resolution is very important for reducing scattered coincidences in the reconstructed image, the image quality attained in a non-TOF LaBr3 scanner can potentially equal or surpass that achieved with other high sensitivity scanners. Our results show that there is a gain in NEC arising from the reduced scatter and random fractions in a LaBr3 scanner. The reconstructed image resolution is slightly worse than a high-Z scintillator, but at increased count-rates, reduced pulse pileup leads to an image resolution similar to that of LSO. Image quality simulations predict reduced contrast for small hot spheres compared to an LSO scanner, but improved noise characteristics at similar clinical activity levels.

Latest Advances in Molecular Imaging Instrumentation

“…According to Equation 1, an improvement in SNR of 2-fold for 40-cm phantoms and 2.5-fold for 60-cm phantoms can be achieved with this system. Kuhn and Surti (53,54) are developing a TOF system based on a fairly new scintillator material, LaBr 3 , which has a scintillation decay time of only 25 ns, compared with the 40 ns of LSO, and is approximately twice as bright. However, this approach is still investigational, and its challenges include the hygroscopic characteristics of LaBr 3 , a stopping power less than that for LSO, and limited production capabilities (55).…”

Design considerations for a limited-angle, dedicated breast, TOF PET scanner

“…The Monte Carlo simulation is based on an EGS4 simulations package which models annihilation photon emission and transmission (with attenuation and scatter) through a geometric phantom, tracks their subsequent passage through a scintillation detector configuration, models the detector light response and point spread function as well as timing resolution, and outputs a list-mode data set where each event is tagged as scattered (in the phantom) or true (unscattered) event (Adam and Watson, 1999, Surti et al, 2004, Surti et al, 2006. In this work we reconstructed only the true coincidences.…”

Multi-CFD Timing Estimators for PET Block Detectors

“…In particular, the transit time variations between photomultiplier tubes are a small fraction of the overall timing resolution (108 ps RMS transit time variation compared to ~1.1 ns fwhm coincidence timing resolution), so our measurements are relatively insensitive to the methods used to correct for transit time variation. For TOF PET systems that have better timing resolution [21][22][23]31], these corrections will be much more important. However, we believe that they reasonably represent existing LSO-based PET detector modules.…”

“…resolutions [10][11][12][13][14][15][16][17][18][19][20][21][22][23] this can be an appreciable source of timing jitter.…”