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Computed Tomography Angiography (CTA) of the heart is a non-invasive procedure to rule out coronary artery disease or measure its extent and plan treatments and interventions. The need for coronary tree tracking methods that require minimum human interaction and produce accurate and robust measurements is therefore of great clinical importance. In this work we present a probabilistic coronary artery...
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...
Variable resolution x-ray (VRX) CT is a newly introduced CT scanner that provides increased spatial resolution. Compton scatter poses a significant threat to VRX CT, bringing cupping and streak artifacts. Appropriate compensation of scattered radiation in VRX CT needs accurate estimation of Compton scattering. The aim of this study is to assess the magnitude and spatial distribution of scattered radiation...
The influence of material assignment in a patient geometry for hadron therapy had been studied using GEANT4 simulation. For the purpose of evaluating the influence of material differences, the dose distributions by proton and carbon beams were compared in a homogeneous medium for water and tissue materials, where all mass densities were normalized to 1 g/cm3. The differences were observed in the depth...
The Geant4 simulation toolkit has been widely accepted in particle therapy domain for more accurate treatment planning. In Japan, the PTSIM, Particle Therapy System Simulation Framework, has been developed by the fund from the Core Research for Evolutional Science and Technology of Japan Science and Technology Agency, JST/CREST. The PTSIM provides a common platform to model beam delivery systems including...
A collimation device for 511 keV small animal SPECT/CT using clinical detectors was investigated as an alternative to dedicated PET/CT. The device consists of a 45 mm thick collimator (lead cylinder with 30 tungsten pinhole inserts) and an animal bed with three-degrees-of-freedom. The device rests on the patient bed of a clinical SPECT/CT scanner, where the gamma cameras rotate around the collimator...
Scatter artifacts impair the CT image quality and the accuracy of CT values. Especially in cases with metal implants and in wide cone-angle flat detector CT scans, scatter artifact removal can be of great value. Typical scatter correction methods try to estimate scattered radiation and subtract the estimated scatter from the uncorrected data. Scatter is found either by time-consuming Monte Carlo-based...
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...
Many researchers have been studying on the noise properties and image quality influence on system performance for tomographic imaging in recent years. Most of the works are focused on 2D nuclear medicine imaging. Since X-ray CT dosage has been pushed to a lower level and 3D imaging has been a trend, it is necessary to study the performance of 3D X-ray CT systems. In this work, we presented a new theoretical...
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,...
Conventional x-ray detectors integrate the photon energy flux, losing individual photon energy information. By contrast, energy resolved photon-counting x-ray detectors (PCXDs) count photons in energy windows, thus retaining some energy information. This provides a number of advantages, including the use of energy information to aid in material discrimination. However, this capability relies on accurately...
The use of electron beams with energies of 150-250 MeV, called Very High Energy Electrons (VHEE), has been proposed as a new modality for radiation therapy of cancer. VHEE modality may have potential advantages for tumor irradiation compared with conventional megavoltage photon or proton therapy. The Monte Carlo simulation of the VHEE application is currently the only available option for treatment...
An X-ray computed tomography (CT) simulator based on Geant4 toolkit was developed for simulation of both fan- and cone-beam CT scanners. There major components X-ray tube, phantom and detector are simulated. Different to analytical simulation, this simulation is accordance with imaging physics by adopting the Geant4 toolkit. Compared with ordinary statistical simulation, acceleration investigation...
The segmentation of vascular structures in 3D medical images is of great importance for many clinical applications, ranging from the detection and measurement of vascular disease to providing information for surgical intervention. Accurate and robust vascular segmentation is made difficult by variations in the vessel's contrast enhancement and its surrounding background, both within the same patient...
This paper uses experiment design optimization to obtain the optimal placement of scans during dynamic contrast enhanced computed tomography. Here we construct and minimize an objective function based on the Cramer-Rao lower bound (CRLB) to optimize the accuracy of the estimators. Experiments based on simulated data are performed to compare our scheme with current sampling methods. Results reveal...
The presentation summarizes our achieved results within the framework of the cross-institutional research project called TeraTomo. The aim of the latter is to create a high-speed algorithm optimized on graphics processors (GPU) providing more accurate PET reconstructions by taking advantage from CT data. The current paper discusses a hit-and-miss Monte Carlo approach as an "on-the-fly" forward...
Monte Carlo simulations of X-ray irradiations of breast phantoms of various sizes as PMMA cylinders of different diameters and a hemi-ellipsoidal PMMA phantom were performed in order to evaluate the 2D distribution of primary and scattered photons and Scatter-to-Primary Ratio (SPR) in projection images in cone-beam breast CT. Irradiation geometry and technique factors were set so as to reproduce the...
Motion correction of the abdominal-thoracic region is one of the main research challenges in tomographic nuclear medicine imaging. We address this issue with a flexible data-driven method of motion correction. This uses marker-less stereo tracking of the anterior abdominal-chest surface and a 'virtual dissection'-based registration approach, combined within a novel paricle filtering (PF) framework...
An efficient simulation tool is developed to generate realistic X-ray CT images, including a good modeling of physics and a very detailed anthropomorphic model in a reasonable computing time. This simulation tool consists in a coupling of the existing X-ray radiographic simulation software SINDBAD with the extended NURBS-Based Cardiac-Torso (XCAT) phantom. Both primary and scatter contributions in...
In this study, we present a small animal hybrid PET/CT scanner for simultaneous X and gamma ray scans of the same field of view. It is based on the high resolution PET scanner demonstrator ClearPET developed within the Crystal Clear Collaboration and on the prototype X-ray hybrid pixel detector XPAD3 developed at CPPM. The complete hybrid system has been studied using the GATE Monte Carlo simulation...
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