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.