Angulated Gothic aortic arch is associated with increased systolic wave reflection, as well as increased central aortic stiffness and left ventricular mass index. These findings explain (at least in part) the association between this pattern of arch geometry and late hypertension at rest and on exercise in subjects after coarctation repair.

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International audienceQuantitative reconstruction values are often miscalculated in Cone Beam Computed Tomography (CBCT) due to the presence of secondary radiation originating from scattering of photons inside the object and detector under consideration. The effect becomes more prominent and challenging in case of X-ray source of high energy (over a few 100 keV) which is used in industrial Non-Destructive Testing (NDT), due to higher scatter to primary ratio (SPR). This paper describes a scatter correction algorithm for correcting the combined scattering due to the object and the detector based on variations in Scatter Kernel Superposition (SKS) method. Scatter correction is performed for homogeneous and heterogeneous objects in a robust iterative manner suitable for high SPR, using pencil beam kernels which are simulated in computed tomography (CT) module of the CIVA software for NDT simulations. Two methods for scatter correction using SKS approach are discussed and compared in the paper. In the first method, we use a discrete approach in which kernels for only few thicknesses are used. In the second method a continuous approach is proposed where the kernels are analytically parameterised for all thicknesses. The results obtained after scatter correction are well within the expected reconstruction values. The continuous method produces better edge enhanced corrected projections and the method results in improved reconstruction values than the discrete method

Measurements of pressure variations within the cardiac chambers could provide important information for clinical assessments of cardiovascular function. In this work an MRI method for evaluating spatial distributions of intracardiac relative pressure is presented. We first calculated pressure gradients from MR maps of blood acceleration by applying the NS equation. We then used an original algorithm to compute pressure distribution in a region of interest (ROI) by minimizing the pressure gradient curl so that the result in a given pixel is independent of the integration path. Blood pressure distribution within the left ventricle (LV) reflects the LV relaxation, compliance, and contractility. An early diastolic intraventricular pressure gradient between the base and apex of the LV was described in a previous study using catheters (1), and subsequent studies have confirmed the merit of catheterization to characterize LV filling (2). It has also been shown that this gradient during early systole is a good index of the LV contractility (3,4). Blood pressure is commonly measured with highfidelity pressure transducers that measure the systolic and diastolic pressure at specific locations in the cardiovascular system. Although this procedure is invasive, it remains the gold standard for pressure measurements. However, flow imaging techniques, such as ultrasound Doppler or MR velocimetry, may enable clinicians to noninvasively measure and map blood pressure in the cardiac cavities, thus reducing the costs and risks associated with catheterization.With the use of fluid dynamics and ultrasound Doppler, the pressure gradient across a vessel stenosis or restrictive valve orifice can be clinically estimated by means of a simplified form of the Bernoulli equation and the peak velocity data in the distal flow jet. However, such estimations provide no information about temporal and/or spatial changes in pressure. Many MR methods have been proposed to obtain such information. Two main approaches, both based on the Navier-Stokes (NS) equation (5), have emerged, as described below.The first method, which was extensively studied by Urchuk and Plewes (6) and Urchuk et al. (7), uses the NS equation to estimate pulse pressure gradients within vessel segments. Time-dependent pressure variations across a vessel section in the direction of blood flow are estimated from measurements of vascular compliance and vessel dilation with the use of the Euler equation. These measurements are based on the relationship between the spatial and temporal derivatives of velocity and the mean velocity gradient in the flow direction. This method, which has been used only in the aorta, does not provide a pressure map, but rather a spatial average of the pressure at several locations along the artery.The second MR approach uses the NS equation to calculate pressure gradients from 2D or 4D phase contrast (PC) velocity vector maps (8 -11). Thus, the relative pressure distribution can be computed from the pressure gradients in a region of interest (ROI). This ...