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The impact upon axial image resolution for the TOFPET portion of TOF-PET/CT (time-of-flight positron emission tomography / computed tomography) via continuous bed motion (CBM) due to finer axial/planar sampling in the projection space is examined. We try a 1.6x finer axial sampling pitch in the rebinning step (0.125cm instead of 0.2cm) and show a (slight) 6.5% improvement in full-width-half-maximum...
We developed a Monte Carlo simulation based scatter correction method for 3D list-mode image reconstruction, and tested the method with Monte Carlo simulations. First, an emission image without scatter correction was reconstructed using MLEM. A transmission image was generated with the CT image. Then, based on the emission and transmission images, GATE was used to simulate coincidence events with...
This paper presents a feasible method and validated algorithm for the Open Electrical Impedance Tomography (OEIT) problem which will reduce the computational complexity and the errors in employing the Maxwell equations and implementing the boundary conditions under test. Considering the tested area of skin could be assumed as a plate condenser. So the model like this often exists some fringe effects...
Compact SPECT systems with cadmium zinc telluride (CZT) solid-state detectors with improved energy resolution and shorter acquisition times have recently been introduced. These systems have, however, different energy characteristics compared to NaI(Tl) crystal-based cameras. There is therefore a need to develop new simulation models for these cameras. We modeled the charge transport within the CZT...
There are recurring phenomena in medical imaging, which benefit from robust, descriptive mathematical models. These models serve, for instance, in pulse characterization, relative comparison, mathematical convolution/deconvolution, parametric and Monte Carlo simulation, and circuit design. As a rule, these phenomena share a signal rise which is somewhat exponential in shape, which succumbs to a competing...
Our previous work in dynamic cardiac SPECT imaging of rats with 123I-MIBG showed that with a slow rotation camera (dual head acquisition with 90s per rotation and a 1s acquisition interval at each angle) we could accurately obtain the time activity curves (TACs) and estimate compartmental model parameters. However, the long acquisition time (usually exceeding 60 rotations) limits the throughput and...
The reduction of detectors in PET systems, without significantly compromising the PET utility, is an important cost consideration in a PET-system design. Recent advances in algorithm development can be used for enabling the design and assessment of innovative PET systems. In this work, we investigate PET configurations with reduced number of detectors by using the ASD-POCS algorithm that was developed...
Previously, methods have been proposed for the direct reconstruction of the activity in a set of regions-of-interest (ROI), given the raw emission data and the locations of these ROIs in image space. These methods work well if the ROIs are well aligned, but artifacts may result if the alignment is poor. In this contribution, we propose a maximum likelihood reconstruction algorithm that estimates ROI-values...
In our previous work, we have proposed a stationary panel positron emission tomography (PET) for human body imaging. Besides the large solid angle, the panel PET also provides an open geometry which allows other operations being performed simultaneously during a PET scanning. However, the main challenge of panel PET is the limited view problem. Images reconstructed using traditional algorithms will...
The long object imaging problem in volumetric CT using iterative reconstruction algorithm is a challenge due to the intrinsic longitudinal (z-axis) truncation in the circular scanning trajectory. We revisited the problem in this work and proposed a simplified version of our original approach. We simply removed the projection data expansion and empirical weighting scheme in our original method while...
We investigate an ordered subsets algorithm that solves an optimization problem that minimizes a data fidelity term, motivated by maximum likelihood (ML) for Poisson distributed noise in the transmission data, while enforcing a constraint on the image total variation (TV). We refer to this optimization problem as TV-constrained, transmission PML. Due to recent progress in first-order solvers such...
We describe an investigation of the interaction between the effect of magnetic field on PET image resolution (i.e. FWHM and FWTM) on the plane perpendicular to the direction of the field and the intrinsic resolution or Point-Spread-Function (PSF) of PET scanners using Electron Gamma Shower simulations (EGSnrc). Relatively short and long range PET nuclides (e.g. 22Na, 68Ga, and 15O point sources) surrounded...
We have developed a filtering method to reduce RF interference in PET data for simultaneously acquired PET-MR. Data was acquired from a SiPM-based PET detector coupled to LYSO scintillators using a transmission-line readout scheme and high-speed waveform sampling. The detector was placed within a 9.4 T small animal MR system with either copper or no shielding, and PET data from a low-activity 22Na...
We aim at developing practical ways to measure the parameters necessary for data corrections and calibration of a PET scanner with variable geometry (ClearPEM), in order to achieve accurate quantitative images for a large range of imaging tasks using few phantom measurements. We used a decaying cylindrical phantom to determine calibration and dead time factors for a set of acquisition geometries that...
In medical imaging, it has become widely accepted that image quality should be assessed using a task-based approach in which, for example, one evaluates human observer detection accuracy for a specific diagnostic task. These evaluations should be integral part of an imaging system optimization and testing. However, human observer studies with expert readers are costly and time-demanding. Consequently,...
For continuous crystal based PET detector, we develop a Self-organizing Map (SOM) Neural Network Based Positioning Scheme which can achieve 2.07mm average resolution and is feasible for implementation on Field Programmable Gate Array (FPGA). In this paper, we propose the FPGA design of SOM scheme and apply it to our experiment data. Taking advantage of the pipelined and parallel structure, the implementation...
Clinically translatable scintillation detectors employ relatively long crystals (20-30 mm) for increased system sensitivity in whole-body PET. In these high-aspect ratio (HAR) crystals (long and narrow), the degradation in timing performance due to variance in the optical path length of scintillation light is non-negligible. In this work, an accurate, analytical probability density function (p.d.f...
Stticon Photomultiplier (SiPM) is a promising sensor for PET with a number of advantages. A traditional design for PET detector module is using a pixelated scintillator array coupled to a SiPM array, and it is critical to design reflectors between crystals to decode photon event location. Unlike PMT based detectors, the pixelated scintillator array may not necessarily require complex reflector schemes...
Thallium bromide (TlBr) is being investigated for use as room temperature semiconductor gamma-ray spectrometers because of its wide band gap (2.68 eV) and high stopping power. When cooled to −20°C, performance of better than 1% FWHM at 662 keV has been observed on 5×5×5 mm3 pixelated TlBr detectors. Currently, each of nine anode pixels (in a 3 × 3 array) is read out individually through separate preamplifiers,...
The paper describes a CMOS Integrated Circuit designed for interfacing a Silicon Photomultiplier (SiPM) in UMC 180 nm technology. It features a full signal processing architecture containing Pole-Zero Cancellation (PZC) circuit, Peak Detector and Hold circuit and Comparators which one of main purposes is the coincidence recognition. Front-end electronics consists of two separate channels one for each...
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