Feasibility Study of a Small Animal PET Insert Based on a Single LYSO Monolithic Tube

Abstract

There are drawbacks with using a Positron Emission Tomography (PET) scanner design employing the traditional arrangement of multiple detectors in an array format. Typically PET systems are constructed with many regular gaps between the detector modules in a ring or box configuration, with additional axial gaps between the rings. Although this has been significantly reduced with the use of the compact high granularity SiPM photodetector technology, such a scanner design leads to a decrease in the number of annihilation photons that are detected causing lower scanner sensitivity. Moreover, the ability to precisely determine the line of response (LOR) along which the positron annihilated is diminished closer to the detector edges because the spatial resolution there is degraded due to edge effects. This happens for both monolithic based designs, caused by the truncation of the scintillation light distribution, but also for detector blocks that use crystal arrays with a number of elements that are larger than the number of photosensors and, therefore, make use of the light sharing principle. In this report we present a design for a small-animal PET scanner based on a single monolithic annulus-like scintillator that can be used as a PET insert in high-field Magnetic Resonance systems. We provide real data showing the performance improvement when edge-less modules are used. We also describe the specific proposed design for a rodent scanner that employs facetted outside faces in a single LYSO tube. In a further step, in order to support and prove the proposed edgeless geometry, simulations of that scanner have been performed and lately reconstructed showing the advantages of the design.

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.…”

Advances in Preclinical PET Instrumentation

“…92 A more elegant approach, called gapless PET was proposed more recently. 93 To build a gapless PET scanner, a monolithic PET tube is considered instead of individual detection blocks. The simulated scanner is made up of a monolithic LYSO tube (Fig.…”

“…Comparison of the proposed design with conventional polygonal multiblock PET (for the same geometry) indicated 20% reduction in production cost and 30% enhancement in system sensitivity and count rate capability of the scanner. 93 The same concept was also implemented by another group with different geometric parameters. The simulated scanner, called AnnPET, enables 10% sensitivity achieved using a single LYSO annulus with 50 mm inner ring diameter and 72 mm axial extension.…”

Towards quantitative small-animal imaging on hybrid PET/CT and PET/MRI systems

“…solid-state avalanche photodiodes (APDs), analog/digital Silicon PMTs-SiPMs) facilitate the commercialization and availability of fully integrated PET/MRI technology as reviewed recently by Lee et al [28]. Among the available hybrid imaging systems, simultaneous PET/MRI inserts occupied major interest in preclinical trials owing to their ultra-compact configuration, easy installation and relatively lower design cost [7,[28][29][30][31][32][33][34][35][36]. MR Solutions offers an innovative PET insert compatible with MRI up to 9.4 T, for which the PET ring is made up of dual-layered LSO crystals read out by SiPMs [13].…”