Heart disease is the number one killer in the United States, and finding indicators of the disease at an early stage is critical for treatment and prevention. In this paper we evaluate visualization ...techniques that enable the diagnosis of coronary artery disease. A key physical quantity of medical interest is endothelial shear stress (ESS). Low ESS has been associated with sites of lesion formation and rapid progression of disease in the coronary arteries. Having effective visualizations of a patient's ESS data is vital for the quick and thorough non-invasive evaluation by a cardiologist. We present a task taxonomy for hemodynamics based on a formative user study with domain experts. Based on the results of this study we developed HemoVis, an interactive visualization application for heart disease diagnosis that uses a novel 2D tree diagram representation of coronary artery trees. We present the results of a formal quantitative user study with domain experts that evaluates the effect of 2D versus 3D artery representations and of color maps on identifying regions of low ESS. We show statistically significant results demonstrating that our 2D visualizations are more accurate and efficient than 3D representations, and that a perceptually appropriate color map leads to fewer diagnostic mistakes than a rainbow color map.
Facial allotransplantation replaces missing facial structures with anatomically identical tissues, providing desired functional, esthetic, and psychosocial benefits far superior to those of ...conventional methods. On the basis of very encouraging initial results, it is likely that more procedures will be performed in the near future. Typical candidates have extremely complex vascular anatomy due to severe injury and/or multiple prior reconstructive attempts; thus, each procedure is uniquely determined by the defects and vascular anatomy of the candidate. We detail CT angiography vascular mapping, noting the clinical relevance of the imaging, the angiosome concept and noninvasive delineation of the key vessels, and current controversies related to the vascular anastomoses.
The vascular reorganization after facial transplantation has important implications on future surgical planning. The purpose of this study was to evaluate blood flow (BF) after full face ...transplantation using wide area‐detector computed tomography (CT) techniques. Three subjects with severe craniofacial injury who underwent full face transplantation were included. All subjects underwent a single anastomosis bilaterally of the artery and vein, and the recipient tongue was preserved. Before and after surgery, dynamic volume CT studies were analyzed for vascular anatomy and blood perfusion. Postsurgical CT showed extensive vascular reorganization for external carotid artery (ECA) angiosome; collateral flows from vertebral, ascending pharyngeal or maxillary arteries supplied the branches from the recipient ECAs distal to the ligation. While allograft tissue was slightly less perfused when the facial artery was the only donor artery when compared to an ECA–ECA anastomosis (4.4 ± 0.4% vs. 5.7 ± 0.7%), allograft perfusion was higher than the recipient normal neck tissue. BF for the recipient tongue was maintained from contralateral/donor arteries when the lingual artery was sacrificed. Venous drainage was adequate for all subjects, even when the recipient internal jugular vein was anastomosed in end‐to‐end fashion on one side. In conclusion, dynamic CT identified adequate BF for facial allografts via extensive vascular reorganization.
Dynamic 320‐detector row computed tomography angiography noninvasively identifies adequate blood flow with extensive vascular reorganization in three patients imaged one year after successful full face transplantation.
PurposeTo investigate the tissue-like multiexponential T-2 signal decays in avian eggs. MethodsTransverse relaxation studies of raw, soft-boiled and hard-boiled eggs were performed at 3 Tesla using a ...three-dimensional Carr-Purcell-Meiboom-Gill imaging sequence. Signal decays over a TE range of 11 to 354 ms were fitted assuming single- and multicomponent signal decays with up to three separately decaying components. Fat saturation was used to facilitate spectral assignment of observed decay components. ResultsEgg white, yolk and the centrally located latebra all demonstrate nonmonoexponential T-2 decays. Specifically, egg white exhibits two-component decays with intermediate and long T-2 times. Meanwhile, yolk and latebra are generally best characterized with triexponential decays, with short, intermediate and very long T-2 decay times. Fat saturation revealed that the intermediate component of yolk could be attributed to lipids. Cooking of the egg profoundly altered the decay curves. ConclusionAvian egg T-2 decay curves cover a wide range of decay times. Observed T-2 components in yolk and latebra as short as 10 ms, may prove valuable for testing clinical sequences designed to measure short T-2 components, such as myelin-associated water in the brain. Thus we propose that the egg can be a versatile and widely available MR transverse relaxation phantom. Magn Reson Med 75:2156-2164, 2016. (c) 2015 Wiley Periodicals, Inc.
Purpose:
To validate Computed Tomography Fractional Flow Reserve (CT-FFR) measurements with accurate 3D printed coronary phantoms.
Methods:
DICOM data from four phases in two patients imaged with a ...standard 320 × 0.5mm coronary CT acquisition (70–80% cardiac cycle) underwent semi-automated segmentation using a research workstation. Both patients had a >50% stenosis from the clinical image interpretation. Each volume was saved as a Stereo Lithographic (STL) file with 250 micron resolution. The 3D geometries were qualitatively assessed; the best of the four phases was 3D printed using a Stratasys Eden260V printer in Tango+, a rubber-like material that roughly emulates mechanical properties of human vasculature. We connected the model to a programmable pump and measured the pressure drop using pressure sensors embedded proximal and distal to the arterial stenosis. Next, the STL files used for the 3D printed models were uploaded in the ANSYS meshing tool (ICEM CFD 16.1). A standard meshing process was applied and the meshed geometry was directly imported in the ANSYS Fluent for Computational Flow Dynamics simulations. The CFD simulations were used to calculate the CT-FFR and compared to the bench top FFR measured in the 3D printed phantoms.
Results:
FFR-CT measurements and phantoms were completed in within an hour after the segmentation. Patient 1 had a 60% stenosis that resulted in a CT-FFR of 0.68. The second case had a 50% stenosis and a CT-FFR of 0.75. The average bench top FFR measurements were 0.72 and 0.80, respectively.
Conclusion:
This pilot investigation demonstrated the use of a bench-top coronary model for CT-FFR validation. The measurements and the CFD simulations agreed within 6%. Project supported by Support: Toshiba America Medical Systems Corp.and NIH grant R01-EB002873.
Project supported by Toshiba America Medical Systems Corp.and partial support from NIH grant R01-EB002873
The results of numerical simulations are presented which demonstrate that liquid-mirror telescope galaxy redshift surveys such as the current UBC-NASA multi-narrow-band survey and the future Large ...Zenith Telescope (LZT) survey have the potential of discriminating between the predictions of different theories of structure formation. Most of the currently studied theories of structure formation predict a scale-invariant spectrum of primordial perturbations. Therefore, to distinguish between the predictions of the various models, we make use of statistics that are sensitive to non-Gaussian phases, such as the counts-in-cell statistics, N-galaxy probability functions and Minkowski functionals. It is shown that already the current UBC-NASA survey can clearly differentiate between the predictions of some topological defect theories and those of inflationary Universe models with Gaussian phases.
Fast spin echo (FSE) trains elicited by nonselective "hard" refocusing radio frequency (RF) pulses have been proposed as a means to enable application of FSE methods for high-resolution 3D magnetic ...resonance imaging (MRI). Hard-pulse FSE (HPFSE) trains offer short
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echo spacings, but are unfortunately limited to imaging the entire sample within the coil sensitivity thus requiring lengthy imaging times, consequently limiting clinical application. In this work we formulate and analyze two general-purpose combinations of 3D HPFSE with inner volume (IV) MR imaging to circumvent this limitation. The first method employs a 2D selective RF excitation followed by the HPFSE train and focuses on required properties of the spatial excitation profile with respect to limiting RF pulse duration in the
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range. The second method employs two orthogonally selective 1D RF excitations (a
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pair) to generate an echo from magnetization within the volume defined by their intersection. Subsequent echoes are formed via the HPFSE train, placing the focus of the method on (a) avoiding spurious echoes that may arise from transverse magnetization located outside the slab intersection when it is unavoidably affected by the nonselective refocusing pulses and (b) avoiding signal losses due to the necessarily different spacing (in time) of the RF pulse applications. The performance of each method is experimentally measured using Carr-Purcell-Meiboom-Gill (CPMG) multi-echo imaging, enabling examination of the magnetization evolution throughout the echo train. The methods as implemented achieve 95% to 97% outer volume signal suppression, and higher suppression appears to be well within reach, by further refinement of the selective RF excitations. Example images of the human brain and spine are presented with each technique. We conclude that the SNR efficiency of volume imaging in conjunction with the short echo spacing afforded by hard pulse trains enables high-resolution 3D HPFSE MRI of a small field-of-view (FOV) with minimal aliasing artifact.
We report initial surgical planning computed tomographic protocols for composite tissue allotransplantation of the face. This complex procedure replaces missing facial structures with anatomically ...identical tissues, restoring form and function. Achieved results are superior to those accomplished with conventional techniques. As a growing number of patients/recipients have undergone multiple reconstructions, vascular imaging plays an increasingly critical role in surgical planning and successful execution of the operation.
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