A preclinical PET detector constructed with a monolithic scintillator ring

Abstract

This paper presents a unique preclinical positron emission tomography (PET) detector constructed with a monolithic scintillator ring (MSR) and two rings of silicon photomultipliers (SiPM). The inner diameter, outer diameter and length of the MSR were 48.5 mm, 58.5 mm, and 25.1 mm, respectively. The two SiPM rings, constructed with 46 SiPMs, were air-coupled to the two ends of the MSR detector. The center of gravity (COG) and artificial neural network (ANN) methods were adapted to decode the positions of the gamma interactions in the circumferential (θ) and axial (Z) directions, respectively. Collimating systems, consisting of a tungsten collimator and a highprecision displacement and rotating platform, were constructed to assess the decoding accuracies of the MSR detector in both θ and Z directions. The average intrinsic full-width half maximums (FWHMs) and mean absolute errors (MAEs) of the decoding accuracies were 0.94 mm and 0.33 mm in the circumferential direction, 2.45 mm and 1.08 mm in the axial direction. An energy resolution of 10.7% was measured at 511 keV. The scintillating photons generated by a pair of coincidence gamma photons overlap with each other, and cause circumferential parallax errors in the lines of response (LOR). The experimental results show that the average FWHM errors in the θ direction increased slightly from 0.94 mm to 1.14 mm when Δθ of the two single events was larger than 70°. The imaging performance of the MSR detector was also initially assessed with a Derenzo phantom filled with 18 F-FDG. The rods with a diameter larger than 1.2 mm can be resolved. The energy resolutions were 12.3% at 511 keV (single events), and 11.4% at 1022 keV (coincidence events). We concluded that it is feasible to construct the high-performance preclinical PET scanners using one or multiple MSR detectors.

Novel preclinical PET geometrical concept using a monolithic scintillator crystal offering concurrent enhancement in spatial resolution and detection sensitivity: a simulation study

“…This issue plays a more important role when photons with higher energy, and consequently lower linear attenuation coefficient, are supposed to be detected. However, increasing the thickness of the detector elements would influence the accuracy of the estimated position of interaction owing to increased parallax effect (Xu et al 2019).…”

Performance Evaluation of a PET of 7T Bruker Micro-PET/MR Based on NEMA NU 4-2008 Standards

“…Figure 1 exhibits a picture of our Bruker small animal 7T PET/MRI machine, Ettlingen, Germany. The scanner consists of a patented continuous LYSO crystal [4,16,17] instead of traditional pixelated crystal. It is a stationary system that contains three detector rings in a cylindrical shape.…”

“…In preclinical study and medical applications, PET and MRI are investigated jointly as hybrid imaging modalities. Preclinical PET imaging studies have been significantly improved by using various new technologies, including SiPM [3][4][5][6][7]. Advanced SiPM-based PET technology can provide high-resolution information in brain imaging studies.…”

Energy spectra due to the intrinsic radiation of LYSO/LSO scintillators for a wide range of crystal sizes

“…This result could potentially be extended to other crystal geometries such as monolithic truncated pyramids commonly used in PET scanners that have detectors arranged in rings (see Table III). Further research can also encompass an analysis of more innovative and complex geometries including continuous LYSO crystal tubes 60,61 to predict the analytical shape of the energy spectrum due to the natural radioactivity.…”