Preclinical studies using a prototype high-resolution PET system with Depth of Interaction

et al. 2015

Phys. Med. Biol.

A common approach to improving the spatial resolution of small animal PET scanners is to reduce the size of scintillation crystals and/or employ high resolution pixellated semiconductor detectors. The large number of detector elements results in the system matrix-an essential part of statistical iterative reconstruction algorithms-becoming impractically large. In this paper, we propose a methodology for system matrix modelling which utilises a virtual single-layer detector ring to greatly reduce the size of the system matrix without sacrificing precision. Two methods for populating the system matrix are compared; the first utilises a geometrically-derived system matrix based on Siddon's ray tracer method with the addition of an accurate detector response function, while the second uses Monte Carlo simulation to populate the system matrix. The effectiveness of both variations of the proposed technique is demonstrated via simulations of PETiPIX, an ultra high spatial resolution small animal PET scanner featuring high-resolution DoI capabilities, which has previously been simulated and characterised using classical image reconstruction methods. Compression factors of × 5 10 7 and × 2.5 10 7 are achieved using this methodology for the system matrices produced using the Institute of Physics and Engineering in MedicineContent from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. geometric and Monte Carlo-based approaches, respectively, requiring a total of 0.5-1.2 GB of memory-resident storage. Images reconstructed from Monte Carlo simulations of various point source and phantom models, produced using system matrices generated via both geometric and simulation methods, are used to evaluate the quality of the resulting system matrix in terms of achievable spatial resolution and the CRC, CoV and CW-SSIM index image quality metrics. The Monte Carlo-based system matrix is shown to provide the best image quality at the cost of substantial one-off computational effort and a lower (but still practical) compression factor. Finally, a straightforward extension of the virtual ring method to a three dimensional virtual cylinder is demonstrated using a 3D DoI PET scanner.

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Section: Validation With 3d Doi Petmentioning

confidence: 99%

A new virtual ring-based system matrix generator for iterative image reconstruction in high resolution small volume PET systems

et al. 2015

Phys. Med. Biol.

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“…Conventional small animal PET scanners are based on scintillation detectors, in which scintillator materials such as LSO, LYSO or BGO are optically coupled to position-sensitive photomultiplier tubes or silicon photomultipliers. These scanners are capable of providing a spatial resolution of 1 to 2 mm FWHM [2][3][4][5][6][7][8][9][10][11]. However, achieving sub-millimetre spatial resolution using scintillation detectors is a challenge due to the variation of scintillation light collection efficiency, intra-crystal Compton or coherent scattering, inter-crystal Compton scattering, and limited depth-of-interaction (DoI) information [12,13].…”

Section: Introductionmentioning

confidence: 99%

A feasibility study of PETiPIX: an ultra high resolution small animal PET scanner

et al. 2013

J. Inst.

PETiPIX is an ultra high spatial resolution positron emission tomography (PET) scanner designed for imaging mice brains. Four Timepix pixellated silicon detector modules are placed in an edge-on configuration to form a scanner with a field of view (FoV) 15 mm in diameter. Each detector module consists of 256×256 pixels with dimensions of 55×55×300 µm 3 . Monte Carlo simulations using GEANT4 Application for Tomographic Emission (GATE) were performed to evaluate the feasibility of the PETiPIX design, including estimation of system sensitivity, angular dependence, spatial resolution (point source, hot and cold phantom studies) and evaluation of potential detector shield designs. Initial experimental work also established that scattered photons and recoil electrons could be detected using a single edge-on Timepix detector with a positron source. Simulation results estimate a spatial resolution of 0.26 mm full width at half maximum (FWHM) at the centre of FoV and 0.29 mm FWHM overall spatial resolution with sensitivity of 0.01%, and indicate that a 1.5 mm thick tungsten shield parallel to the detectors will absorb the majority of non-coplanar annihilation photons, significantly reducing the rates of randoms. Results from the simulated phantom studies demonstrate that PETiPIX is a promising design for studies demanding high resolution images of mice brains.

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Design and development of PETiPIX: An ultra high spatial resolution small animal PET scanner

2013 IEEE Nuclear Science Symposium and Medical Imaging Conference (2013 NSS/MIC)

et al. 2013