A method of computing the velocity field and pressure distribution from a sequence of ultrafast CT (UFCT) cardiac images is demonstrated. UFCT multi-slice cine imaging gives a series of tomographic slices covering the volume of the heart at a rate of 17 frames per second. The complete volume data set can be modeled using equations of continuum theory and through regularization, velocity vectors of both blood and tissue can be determined at each voxel in the volume. The authors present a technique to determine the pressure distribution throughout the volume of the left ventricle using the computed velocity field. A numerical algorithm is developed by discretizing the pressure Poisson equation (PPE), which Is based on the Navier-Stokes equation. The algorithm is evaluated using a mathematical phantom of known velocity and pressure-Couette flow. It is shown that the algorithm based on the PPE can reconstruct the pressure distribution using only the velocity data. Furthermore, the PPE is shown to be robust in the presence of noise. The velocity field and pressure distribution derived from a UFCT study of a patient are also presented.
CT scans were obtained with a Cine-CT Scanner that uses a rapidly moving focused electron beam. The 50-msec CT scans were obtained at two transverse levels simultaneously through the hearts of a series of four normal dogs and six patients, four with coronary artery disease and two with hypertrophic cardiomyopathy. Two scanning mode options were chosen. Myocardial wall thickening and motion were studied by obtaining ten 50-msec CT exposures during one heart-beat within less than one second (cine-CT mode). Regional myocardial blood flow was assessed by obtaining approximately 20 scans at the same level of the left ventricle; each 50-msec exposure was gated to the same phase of 20 sequential heartbeats after intravenous administration of contrast medium (dynamic mode). These initial studies show the feasibility of defining regional and global myocardial contraction using the cine-CT mode, and the considerable potential for measuring regional myocardial perfusion using the flow (dynamic) mode.
Computed tomographic (CT) scans of fresh and coagulated blood in vitro as well as calcium and iron solutions demonstrate that the increased absorption seen in hematomas is primarily a reflection of hemoconcentration: calcium plays essentially no role in this increased absorption, while iron makes a minimal contribution. In vitro studies of cerebrospinal fluid (CSF) indicate that CT scanning is insensitive to pathological elevations of CSF protein.
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