Evaluation of event position reconstruction in monolithic crystals that are optically coupled

Abstract

A PET detector featuring a pseudo-monolithic crystal is being developed as a more cost-effective alternative to a full monolithic crystal PET detector . This work evaluates different methods to localize the scintillation events in quartered monolithic crystals that are optically coupled. A semi-monolithic crystal assembly was formed using four 26 × 26 × 10 mm3 LYSO crystals optically coupled together using optical adhesive, to mimic a 52 × 52 × 10 mm3 monolithic crystal detector. The crystal assembly was coupled to a 64-channel multi-anode photomultiplier tube using silicon grease. The detector was calibrated using a 34 × 34 scan grid. Events were first filtered and depth separated using a multi-Lorentzian fit to the collected light distribution. Next, three different techniques were explored to generate the look up tables for the event positioning. The first technique was 'standard interpolation' across the interface. The second technique was 'central extrapolation', where a bin was placed at the midpoint of the interface and events positioned within the interface region were discarded. The third technique used a 'central overlap' method where an extended region was extrapolated at each interface. Events were then positioned using least-squares minimization and maximum likelihood methods. The least-squares minimization applied to the look up table generated with the standard interpolation technique had the best full width at half maximum (FWHM) intrinsic spatial resolution and the lowest bias. However, there were discontinuities in the event positioning that would most likely lead to artifacts in the reconstructed image. The central extrapolation technique also had discontinuities and a 30% sensitivity loss near the crystal-crystal interfaces. The central overlap technique had slightly degraded performance metrics, but it still provided ~2.1 mm intrinsic spatial resolution at the crystal-crystal interface and had a symmetric and continuously varying response function. Results using maximum likelihood positioning were similar to least-squares minimization for the central overlap data.

Machine Learning aided 3D-position reconstruction in large LaCl$_{3}$ crystals

“…The results obtained with the analytical models for the 10 mm thick LaCl 3 (Ce) crystal are similar to the ones obtained in our previous work [18]. Also, they are comparable to similar studies that involve thin crystals [17,61,62]. However, the results obtained for Keras are significantly worse.…”

Efficient Strike Artifact Reduction Based on 3D-Morphological Structure Operators from Filtered Back-Projection PET Images

“…Positron emission tomography (PET) can provide functional images and identify abnormal metabolic regions of the whole body that effectively detect the presence and distribution of tumors. Because of the use of different radioactive tracers, factors associated with nuclear medicine imaging, including the physical characteristics of photons, data acquisition settings, or reconstruction algorithms that generate artifact noise in images, can easily interfere with the image quality [1][2][3][4][5][6][7]. Common noise models in PET scans include Gaussian, Poisson, and mixed noise.…”

Development of depth encoding small animal PET detectors using dual‐ended readout of pixelated scintillator arrays with SiPMs

“…For this reason, much attention in recent years has focused on detector designs with depth-encoding ability. Major depth encoding techniques include multilayer scintillator arrays, [6][7][8][9] monolithic scintillator detector [10][11][12][13] and dualended readout of pixelated scintillator arrays. [14][15][16][17] Dual-ended readout of pixelated scintillator array is one popular depth encoding technology.…”

“…For this reason, much attention in recent years has focused on detector designs with depth‐encoding ability. Major depth encoding techniques include multilayer scintillator arrays, monolithic scintillator detector and dual‐ended readout of pixelated scintillator arrays …”