نتایج جستجو برای: water phantom
تعداد نتایج: 566361 فیلتر نتایج به سال:
The production of high quality pretreatment images plays an increasing role in image-guided radiotherapy (IGRT) and adaptive radiation therapy (ART). Megavoltage cone-beam computed tomography (MV-CBCT) is the simplest solution of all the commercially available volumetric imaging systems for localization. It also suffers the most from relatively poor contrast due to the energy range of the imagi...
Introduction: In the last few decades, a lot of monte carlo codes have been introduced for medical applications. this is important because through simulation, we are fully independent of the spectral scattering factor that we are not able measure in real terms. The effect of the radiation energy, the dimension of the radiation field, the sensitive volume of the ion chamber on t...
Medical imaging plays an important role in patients' care and is continuously being used in managing health and disease. To obtain the maximum benefit from this rapidly developing technology, further research is needed. Ideally, this research should be done in a patient-safe and environment-friendly manner; for example, on phantoms. The goal of this work was to develop a protocol and manufactur...
Introduction Proton resonance frequency shift (PRFS) thermometry of the breast is often confounded not only by the presence of fat in the tissue but also by respiration-induced B0 changes even in the absence of detectable breast motion. We (and others) have measured B0 changes of up to 0.16ppm due to respiration[1] leading to temperature errors on the order of 16°C (due to the 0.01ppm/°C PRFS s...
Diffusion-weighted magnetic resonance imaging (MRI) is frequently used clinically, and is available for the whole-body screening for tumors. The exact mechanism by which the apparent diffusion coefficient (ADC) value decreases in tumorous tissue remains unclear, although various theories have been proposed, including intracellular and extracellular factor theories. It is impossible to distingui...
Z-fiducial phantoms allow three-dimensional ultrasound probe calibration with a single B-scan. One of the main difficulties in using this phantom is the need for reliable segmentation of the wires in the ultrasound images, which necessitates manual intervention. In this article, we have shown how we can solve this problem by mounting a thin rubber membrane on top of the phantom. The membrane is...
PURPOSE Identifying water and fat unambiguously in multipoint Dixon imaging often requires phase correction, which can be challenging and may fail. The purpose of this work is to present a geometric interpretation of the two-point Dixon method with flexible echo times (TEs) and to investigate the conditions under which water and fat can be determined directly without phase correction. METHODS...
Introduction:The commercial 252Cf sources are too large in size and clinical applications of neutronbrachytherapy (NBT) are limited to a small number of intracavitary treatments of cervical cancers. Recently, under the Cooperative Research and Development Agreement (CRADA) with Isotron Inc., the Oak Ridge National Laboratory (ORNL) encapsulated a new medical 252Cf sources, cal...
The purpose of this work was to perform a comprehensive comparison of static field intensity modulated radiation therapy (IMRT) for patient specific quality assurance (QA) in order to investigate commissioning of a XiO treatment planning system (TPS). QA measurements were evaluated for three of four test geometries provided in American Association of Physicists in Medicine (AAPM) Task Group Rep...
A simple robust optimizer has been developed that can produce patient-specific calibration curves to convert x-ray computed tomography (CT) numbers to relative stopping powers (HU-RSPs) for proton therapy treatment planning. The difference between a digitally reconstructed radiograph water-equivalent path length (DRRWEPL) map through the x-ray CT dataset and a proton radiograph (set as the grou...
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