نتایج جستجو برای: Digital NCAT phantom
تعداد نتایج: 324200 فیلتر نتایج به سال:
introduction: poor sensitivity and poor signal to noise ratio because of low injected thallium dose and presence of scattered photons are the main problems in using thallium in scintigraphic imaging of the heart. scattered photons are the main cause of degrading the contrast and resolution in spect imaging that result in error in quantification. thallium decay is very complicated and photons ar...
In radiation therapy of lung tumors, respiratory motion causes target moving, so a larger margin is needed to cover the CTV. With the margin increasing, a larger volume of normal tissue will be exposed to high-dose. In this study, dosimetric parameters of normal lung tissue were compared between gated and conventional radiotherapy (RT), using the NCAT digital phantom. Different series of CT im...
We investigate the effect of heart rate on the quality and artifact generation in coronary artery images obtained using multi-slice computed tomography (MSCT) with the purpose of finding the optimal time resolution for data acquisition. To perform the study, we used the 4D NCAT phantom, a computer model of the normal human anatomy and cardiac and respiratory motions developed in our laboratory....
The cardiac model of the 4D NCAT phantom was enhanced by incorporating a physiological basis from which to realistically model left ventricular (LV) motion defects. A finite element mechanical model of the LV was developed to simulate deficits in contractile function and to study the effect of ischemia on LV function. The model geometry was based on high resolution CT and MRI data sets of a hea...
Introduction: In radiation therapy of lung tumors, respiratory motion causes target moving, so a larger margin is needed to cover the clinical target volume (CTV). With the margin increasing, a larger volume of normal tissue will be exposed to high-dose. In this study, dosimetric parameters of normal lung tissue were compared between gated and conventional radiotherapy (RT), u...
introduction: an efficient method of tomographic imaging in nuclear medicine is positron emission tomography (pet). compared to spect, pet has the advantages of higher levels of sensitivity, spatial resolution and more accurate quantification. however, high noise levels in the image limit its diagnostic utility. noise removal in nuclear medicine is traditionally based on fourier decomposition o...
Magnetic resonance imaging (MRI) simulators have been largely applied to brain studies. However, cardiac applications of these simulators are only emerging. This paper focuses on the realistic simulation of local appearance of cardiac MRI datasets. Simulations are obtained from the MRISIM simulator with XCAT phantom (formerly NCAT) as input. Phantoms are further extended to increase realism of ...
4D Computed Tomography Reconstruction from Few-Projection Data via Temporal Non-local Regularization
4D computed tomography (4D-CT) is an important modality in medical imaging due to its ability to resolve patient anatomy motion in each respiratory phase. Conventionally 4D-CT is accomplished by performing the reconstruction for each phase independently as in a CT reconstruction problem. We propose a new 4D-CT reconstruction algorithm that explicitly takes into account the temporal regularizati...
Patient motion during myocardial SPECT profusion imaging may result in the formation of artifacts in the reconstructed images. This study attempts to present a method on the basis of modeling image frames through optimum-degree polynomial curves and fitting 2D curves to detect and correct heart motion at pixel and subpixel accuracy. To evaluate our method, NCAT phantom was shifted during data a...
The National Center for Asphalt Technology (NCAT) completed a roundrobin study in March to determine the accuracy and precision of the NCAT asphalt content tester. The Center has conducted research since 1990 to develop this test method for determining asphalt content of hot mix asphalt (HMA) mixtures by ignition (See the fall, 1994, issue of Asphalt Technology News). In the ignition method, a ...
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