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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...
Time-dependent measurements of light propagation have been demonstrated to provide more information compared to time- independent, or continuous wave (CW) measurements for image reconstruction, when employing absorption or fluorescence contrast. Time-dependent measurements made in the frequency domain have been experimentally made with good signal-to-noise ratio (SNR) in preclinical and clinical research...
Partial volume averaging is one of the most prevalent artifacts in computed tomography (CT) that threatens the diagnostic interpretation by giving the misleading density of a voxel. This paper proposes a novel approach for reducing of partial volume averaging artifact in CT called dual scan method. The idea behind this work is to acquire two sinograms of the object while detector is slightly shifted...
Multi-pinhole collimation is increasingly being used in SPECT imaging. A wide variety of geometric designs has recently been introduced, which can easily be modeled with the Monte Carlo simulator GATE. However multi-pinhole simulations are still very inefficient with GATE due to the lack of a dedicated variance reduction technique. In this work, we introduced a pinhole forced detection method which...
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...
The simulation of single photon emission computed tomography (SPECT) has traditionally been done using Monte Carlo methods. However, the hybrid deterministic transport code TITAN is being benchmarked for the simulation of SPECT. The TITAN code is referred to as “hybrid” because it uses a discrete ordinates method in the phantom and a simplified ray-tracing algorithm in the air outside of the phantom...
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...
Single photon emission computed tomography (SPECT) has essentially remained an unchanged technology since the introduction of parallel-hole collimation in 1964 and stands to gain significantly from sensitivity improvements. Benefits from improved sensitivity include shorter acquisition times and smaller dose requirements. An order of magnitude increase in sensitivity over conventional technology is...
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...
Scatter estimation and compensation are not new concepts. However a robust and accurate scatter estimation method that easily adapts to all clinically relevant imaging protocols and emission energies are not yet readily available. The goal of this study was to further develop and evaluate the SIMIND scatter estimation (SSE) method. We acquired and simulated two line-sources approximately 8.4 cm apart...
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...
In vivo imaging techniques applied to small animals are important tools in basic research. Scintigraphic planar and tomographic images allow in vivo functional expression of the protocol's effect on the animal's organs to be assessed. In that way, long term dynamical studies can be developed on the same animal, which can be used as its own control, helping to reduce statistical uncertainties, to cut...
Calibration and quality control (QC) of gamma cameras with fixed pinhole collimators presents unique challenges since the usual assumption of uniform flood intensity at the surface of the detector is violated. For the GE Discovery NM 530c*, a fast cardiac SPECT system with multiple pinholes and CZT detectors focused on the heart, the problem is further complicated by the fact that the plane of the...
This work is a status report of the job in progress finalized to the estimation of the dose distribution inside the head of a patient undergoing a high resolution CT (Computed Tomography) for the diagnosis of pathologies related to the inner ear. Geant4 (GEometry ANd Tracking) has been used to simulate the head and propagate the particles in the human tissues. The ear has a very complex structure,...
Different implementations of the receiver operator characteristic (ROC) method in cardiac perfusion SPECT have been described. However, none has attempted to independently assess cardiac function. The aim of this study was, therefore, to design and execute a human observer ROC study that includes the evaluation of cardiac function and perfusion. Due to the lack of a gold standard, our initial design...
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...
We are developing a high resolution and quantitative SPECT for the human brain. The SPECT has two types of detector, a large FOV detector with a parallel collimator and a small FOV detector with a pinhole collimator. A quantitative and high resolution image is reconstructed by the small FOV detector using a supporting image obtained by the large FOV detector. The large FOV detector consists of a Nal(Tl)...
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