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BACKGROUND Whether to perform valve replacement in patients with asymptomatic but severe aortic stenosis is controversial. Therefore, we studied the natural history of this condition to identify predictors of outcome. METHODS During 1994, we identified 128 consecutive patients with asymptomatic, severe aortic stenosis (59 women and 69 men; mean [+/-SD](More)
Reorientation of transaxial cardiac PET images into short-axis images has been shown by other investigators to improve visual identifiability of defects in myocardial tracer uptake. However, quantification of physiologic processes from such reoriented images may be complicated by errors introduced during the reorientation process. Therefore, a quantitative(More)
OBJECTIVE Positron emission tomography (PET), the reference technique for in vivo noninvasive assessment of myocardial perfusion and metabolism, is hampered by limited resolution and low signal-to-noise ratio. Cardiac MR imaging, on the other hand, provides excellent soft-tissue contrast. This study examines the feasibility of combining the information of(More)
A nonlinear mathematical model of arterial blood flow, which can account for tapering, branching, and the presence of stenosed segments, is presented. With the finite-element method, the model equations are transformed into a system of algebraic equations that can be solved on a high-speed digital computer to yield values of pressure and volume rate of flow(More)
This study investigated the use of artificial neural networks (ANN) for image segmentation and spatial temporal contour linking for the detection of endocardial contours on echocardiographic images. Using a backpropagation network, the system was trained with 279 sample regions obtained from eight training images to segment images into either tissue or(More)
UNLABELLED This study presents and evaluates a model-based image analysis method to calculate from gated cardiac (18)F-FDG PET images diastolic and systolic volumes, ejection fraction, and myocardial mass of the left ventricle. The accuracy of these estimates was delineated using measurements obtained by MRI, which was considered the reference standard(More)
UNLABELLED Angiography of patients with typical chest pain reveals normal epicardial coronary arteries in about 20%. Coronary flow reserve (CFR) determination is an elaborate, but helpful, task, as only the evidence of microvascular disease enables appropriate therapy. We prospectively evaluated the incidence of a dysfunctional microcirculation and searched(More)
BACKGROUND Regional myocardial blood flow has been quantified using transaxial positron emission tomographic (PET) imaging and tracer kinetic modeling. However, the use of transaxial images limits the accuracy of regional partial volume corrections and the localization of the quantified regional flow values. The purpose of the present study was to overcome(More)
BACKGROUND Aging is associated with changes of the systolic blood pressure that may increase cardiac work and myocardial blood flow at rest and reduce the myocardial flow reserve. This might be misinterpreted as age-related impairment of the coronary vasodilator capacity. METHODS AND RESULTS Myocardial blood flow was quantified at rest and after(More)
OBJECTIVES This study was performed to determine the feasibility, accuracy and reproducibility of real-time volumetric three-dimensional echocardiography (3-D echo) for the estimation of mitral valve area in patients with mitral valve stenosis. BACKGROUND Planimetry of the mitral valve area (MVA) by two-dimensional echocardiography (2-D echo) requires a(More)