Background: Functional and morphological changes of the heart influence blood flow patterns. Therefore, flow\r\npatterns may carry diagnostic and prognostic information. Three-dimensional, time-resolved, three-directional phase\r\ncontrast cardiovascular magnetic resonance (4D PC-CMR) can image flow patterns with unique detail, and using\r\nnew flow visualization methods may lead to new insights. The aim of this study is to present and validate a novel\r\nvisualization method with a quantitative potential for blood flow from 4D PC-CMR, called Volume Tracking, and\r\ninvestigate if Volume Tracking complements particle tracing, the most common visualization method used today.\r\nMethods: Eight healthy volunteers and one patient with a large apical left ventricular aneurysm underwent 4D PCCMR\r\nflow imaging of the whole heart. Volume Tracking and particle tracing visualizations were compared visually\r\nside-by-side in a visualization software package. To validate Volume Tracking, the number of particle traces that\r\nagreed with the Volume Tracking visualizations was counted and expressed as a percentage of total released\r\nparticles in mid-diastole and end-diastole respectively. Two independent observers described blood flow patterns\r\nin the left ventricle using Volume Tracking visualizations.\r\nResults: Volume Tracking was feasible in all eight healthy volunteers and in the patient. Visually, Volume Tracking\r\nand particle tracing are complementary methods, showing different aspects of the flow. When validated against\r\nparticle tracing, on average 90.5% and 87.8% of the particles agreed with the Volume Tracking surface in middiastole\r\nand end-diastole respectively. Inflow patterns in the left ventricle varied between the subjects, with\r\nexcellent agreement between observers. The left ventricular inflow pattern in the patient differed from the healthy\r\nsubjects.\r\nConclusion: Volume Tracking is a new visualization method for blood flow measured by 4D PC-CMR. Volume\r\nTracking complements and provides incremental information compared to particle tracing that may lead to a\r\nbetter understanding of blood flow and may improve diagnosis and prognosis of cardiovascular diseases.
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