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Traditional whole-body PET scanner is limited in resolution due to large detector crystal size, finite positron range and non-collinearity of annihilation photons. Our lab has developed a prototype half ring insert PET system that can improve resolution and radionuclide contrast recovery by using (1) smaller size of the detector crystals (2) virtual pinhole PET geometry obtained by placing the insert...
The topic of the reconstruction of data acquired in emission tomography is examined in this work. A new statistical estimator of voxel activities is derived assuming Poisson statistics of the data. A Monte Carlo algorithm to calculate the estimator and its covariance is provided. The estimator is based on the calculation of expectations of random variables which differ from commonly used iterative...
A novel way to perform scatter correction for Positron Emission Tomography by using point clouds representation is presented. The scatter correction method is based on single scatter simulation. The strategy of scatter point sampling during scatter calculation will affect the accuracy of scatter correction directly and the number of sampled scatter points determines the computation complexity. Compared...
Quantitative PET imaging usually requires the arterial blood sampling, which is an invasive measure and may introduce risks or other complications to patients. People are trying several non-invasive methods to obtain the quantitative tracer concentrations by measuring the reconstructed intensity of the artery in the PET imaging. However, all these methods have certain limitations for brain study due...
Tomographic reconstruction based on origin ensembles (OE) is a new procedure for estimation of emission intensity distributions from projection measurements. The advantages of this method over standard iterative approaches are shorter computation time and easier implementation of complex system models in emission tomography (ET) inverse problems. The approach is not based on data likelihood, as are...
The objective of this work is to present a region-based image change detection algorithm based on a statistical test for outliers. The performance of the proposed algorithm is compared to the performance of another algorithm we have developed, which is based on the Grubbs statistical test for outliers. The two algorithms are tested on pairs of reconstructed images obtained from realistic Monte Carlo...
GRAY (High Energy Photon Ray Tracer) is a Monte-Carlo ray-driven high energy photon transport engine for PET and SPECT applications that supports complex mesh based primitives for source distributions, phantom shapes, and detector geometries. Ray tracing is a technique used in computer graphics to render scenes with realistic light properties. We adapted this technique to accelerate solving the intersection...
Iterative methods are currently accepted as the gold standard image reconstruction methods in nuclear medicine. The quality of the final reconstructed image greatly depends on how good the physical processes are modelled in the System-Response-Matrix (SRM). Monte-Carlo based methods are a promising approach to calculate the SRM. However, the increasing granularity used in the detector and image space...
We compare two methods with different accuracy in modeling of multiple scatter estimation in 3D PET. In the first approach, the single scatter is obtained from model-based simulation while the multiple scatter projections are estimated by convolving the single scatter projections with a one-dimensional Gaussian kernel. A new convolution kernel model is proposed, in which both the amplitude and width...
COMPET is an innovative implementation of a small animal PET scanner using a novel block detector geometry, allowing for a high resolution and high sensitivity. One detector block is built up from layers of long LYSO crystals. Perpendicular and interleaved between the crystals, Wave Length Shifting (WLS) fibers are used. The scintillation light created by a gamma ray interacting with a crystal is...
Even with the huge advance of computers and computing power, full three dimensional reconstructions of PET and CT scans belong to the future as far as commercially available scanners and software are concerned. Recent investigations have shown that with the aid of Graphical Processing Units (GPUs) extremely high computational speed might be achieved, which lends itself to the implementation of iterative...
Proton therapy is mainly used to treat cancer where a conformal dose is essential. Methods for monitoring both the spatial distribution and the delivered dose have thus been proposed [1]. Proton irradiation on organic tissue produces positron emitters (mainly 11C and 15O). Proton therapy monitoring may thus be performed using Positron Emission Tomography (PET) acquisition. The proposed methods most...
Including anatomical information during emission tomography reconstruction with resolution modeling can enhance the image quality. Often accurate segmentation of the anatomical image is required, being a major challenge for most applications. Recently, we studied a segmentation-free MAP algorithm proposed by Bowsher et al, that encourages similar activity in a selection of neighboring voxels that...
An efficient, two-dimensional, analytic, Spline Reconstruction Technique (SRT) has been presented earlier in the literature. This technique involves the Hilbert transform of the sinogram which is approximated in terms of natural cubic splines. The aim of this study is to evaluate the SRT algorithm using Monte-Carlo simulated sinograms and real PET data, in comparison with three commonly used reconstruction...
3D-PET (Positron Emitter Tomography) is widely used for quantification of myocardial blood flow. Quantification of myocardial blood flow is very important for enhancement of the sensitivity and the specificity. In the case of an O-15 cardiac PET, the heart is placed in the center of a field of view (FOV) and the liver which can be main background is placed outside FOV (OFOV). In a phase, the liver...
This article presents the performance evaluation in planar and tomographic mode, of a low cost dedicated PET camera for small animal imaging. The system consists of two pixelated LSO crystals, two Hamamatsu H8500 PSPMTs, fast amplification electronics and a FPGA based read out system. The main parameters that have been studied are i) saturation as a function of acceptance angle ii) effect of projections...
Software for a Monte Carlo based simulation of a future Time-of-Flight (TOF) Positron Emission Tomography (PET) system's scintillator geometry, multi-pixel silicon photomultiplier and high-speed Analog to Digital Converter (ADC) readout system has been developed. Results from running simulations with different ADC sampling-rates and analog filter time constants are being presented. A trigger-system...
Simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) can provide both functional and structural information about disease. However, for quantitative PET measurements all sources of scatter and absorption that photons undergo on their trajectory between source and detector must be assessed. In simultaneous PET/MR, this includes the scatter and absorption undergone in...
As the dimensions of crystal elements in modern PET systems is getting smaller, the fraction of events undergoing inter-crystal scattering (ICS) and penetration increases. This has deteriorative impact on the spatial resolution of images. However, with the utilization of statistical image reconstruction methods in PET, compensation for ICS and penetration impacts is feasible by accurately modeling...
In human emission tomography, an additional transmission scan is often required to obtain accurate attenuation maps for attenuation correction (AC) and scatter correction (SC). These methods have been translated to small animal imaging, although the impact of photon interactions on the reconstruction of mouse/rat images is substantially less than that in human imaging. In this study, we evaluate the...
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