Feasibility of a novel design of high resolution parallax-free Compton enhanced PET scanner dedicated to brain research

Abstract

A novel concept for a positron emission tomography (PET) camera module is proposed, which provides full 3D reconstruction with high resolution over the total detector volume, free of parallax errors. The key components are a matrix of long scintillator crystals and hybrid photon detectors (HPDs) with matched segmentation and integrated readout electronics. The HPDs read out the two ends of the scintillator package. Both excellent spatial (x, y, z) and energy resolution are obtained. The concept allows enhancing the detection efficiency by reconstructing a significant fraction of events which underwent Compton scattering in the crystals. The proof of concept will first be demonstrated with yttrium orthoaluminate perovskite (YAP):Ce crystals, but the final design will rely on other scintillators more adequate for PET applications (e.g. LSO:Ce or LaBr3:Ce). A promising application of the proposed camera module, which is currently under development, is a high resolution 3D brain PET camera with an axial field-of-view of approximately 15 cm dedicated to brain research. The design philosophy and performance predictions based on analytical calculations and Monte Carlo simulations are presented. Image correction and reconstruction tools required to operate this transmissionless device in a research environment are also discussed. Better or similar performance parameters were obtained compared to other known designs at lower fabrication cost. The axial geometrical concept also seems to be promising for applications such as positron emission mammography.

A segmented hybrid photon detector with integrated auto-triggering front-end electronics for a PET scanner

“…The PET-HPD was operated at 15 kV with an electronic threshold of 30 mV. After quadratic de-convolution of the straggling term discussed above we calculated the number of photoelectrons from N = ENF·(µ/σ) 2 . The good linearity of N vs. pulse length shown in Fig.…”

“…Experimentally, ignoring the straggling effect at high energies, the measured charge distribution can be characterized by a Gaussian with mean value µ = g·N and variance σ = g·(ENF·N) 1/2 , where ENF is the so called Excess Noise Factor (ENF = 1.045 for HPD 5 ). Consequently the number of pe's is simply determined by N = ENF·(µ/σ) 2 . An important advantage of HPDs for the axial PET concept is, as discussed above, the possibility to read out the induced signal on the Si sensor back plane, providing a fast measurement of the total charge deposited in the depleted Si bulk.…”

“…Our PET concept (see [1][2][3]) is based on camera modules consisting of axially oriented matrices of 16 × 13 long polished LYSO 2 scintillator bars (e.g. 3.2 × 3.2 × 150 mm 3 ) optically coupled at both ends to two PETHPDs (see Fig.…”

A novel energy mapping approach for CT‐based attenuation correction in PET

“…The resulting PET images are interpreted visually to assess the physiologic function of tissues, organs, and organ systems or can eventually be evaluated quantitatively to measure biochemical and physiologic processes in vivo. However, several physical factors can degrade image quality and quantitative accuracy of PET images including the detection of Compton Scattered photon, 1 patient motion, 2 attenuation of photons, 3 partial volume effect, 4 parallax effect, 5 positron range, 6 and annihilation photon acollinearity. 7 In particular, attenuation of photons in tissues affects both visual quality and quantitative accuracy of PET images.…”

PeneloPET, a Monte Carlo PET simulation tool based on PENELOPE: features and validation

“…The availability of powerful computers has encouraged the use of PET-dedicated simulation codes in the last few years. Examples of areas that benefit from extensive simulations are the design of new PET scanners (Braem et al 2004, Heinrichs et al 2003, the development and assessment of image reconstruction algorithms (Herraiz et al 2006) and of correction techniques (Levin et al 1995), among other applications (Zaidi 2000, Ay and Zaidi 2006, Ortuño et al 2003, Torres-Espallardo et al 2008. Simulations make it possible not only to refine the design parameters of PET scanners, but they also help to identify bottlenecks regarding count rate, resolution, sensitivity, etc.…”