Effect of Voxel Size, Image Orientation, VENC and TE on Phase Contrast Measurements in Turbulent Stenotic Jets.

Abstract

Aortic stenosis (AS) can give rise to high velocity jets of more than 400cm/s. Phase contrast (PC) has the potential to accurately diagnose lesion severity; however, AS jets are often very turbulent and intravoxel dephasing can introduce significant errors in peak velocity and flow. In an in-vivo investigation of moderate to severe AS patients we found that PC measurements of stroke volume (SV) were systematically lower than SV obtained from volumetric measurements (Figure 1a). In-vitro experiments in a pipe of aortic diameter were able to reproduce these errors. Shortening TE, (Figure 1b) was shown to increase signal and improve accuracy; however, the relative influence of factors contributing to the signal loss and errors remains uncertain [1-3]. Purpose: To investigate, using up-to-date gradient hardware, the influence of voxel size [1], velocity encoding (VENC) [2], and orientation of the jet relative to the image plane [3], all of which have previously been found to cause signal loss and intravoxel dephasing in high velocity turbulent jets.