The Essence of Half-FOV Shift Ghost Imaging

Introduction: Ghost imaging and especially its applications to MR angiography (MRA) have been proposed as an improvement over the conventional magnitude subtraction based imaging methods, such as Fresh Blood Imaging (FBI) [1]. There are basically two types of ghost MRA; type I and II. Type I is usually performed without gating, by summing outside the body ghost artifacts created from uncontrolled variations of flow and other natural phenomena that are shifted pseudo-randomly in distance along a single direction perpendicular to the direction of ghost generation [2-3]. Type II aims to create controlled flow-induced changes between the even and the odd k-space lines, to create systematically controlled 1⁄2 FOV shifts, which projects as a 3D ghost differential image outside the body, that can be maximum intensity projection (MIP) processed along multiple angles [4]-[7]. The latter was reported to show superior background suppression and allowed higher parallel imaging acceleration factors.