2.3.3 MSCT
Measurements of the aortic annulus were obtained manually on a dedicated viewing station (Philips Extended Brilliance Workspace) using multi-planar reconstruction. A dataset of images produced by a scan throughout the cardiac cycle was reviewed for quality and artefact. A suitable subset was then selected in the diastolic phase (commonly at the 30 to 35% point in the cardiac cycle). Using multi-planar reconstruction of the selected dataset, the plane of the annulus was determined by selecting the basal attachments (hinge points) of the 3 aortic valve cusps. The 3 hinge points were then connected by a smooth curved line to create an ellipse along the periphery of the intra-aortic x-ray contrast density, the ellipse defining the perimeter of the virtual annulus. Three measurements were then obtained in that plane viz. maximal and minimal diameters, perimeter and cross sectional area.