A dual‐projection respiratory self‐gating technique for whole‐heart coronary MRA

Abstract

Purpose:To investigate the accuracy of a dual-projection respiratory self-gating (DP-RSG) technique in dynamic heart position measurement and its feasibility for freebreathing whole-heart coronary MR angiography (MRA). Materials and Methods:A DP-RSG method is proposed to enable accurate direct measurement of heart position by acquiring two whole-heart projections. On 14 volunteers we quantitatively evaluated the efficacy of DP-RSG by comparison with diaphragmatic navigator (NAV) and single-projection-based respiratory self-gating (SP-RSG) methods. For DP-RSG we also compared center-of-mass and two profilematching algorithms in deriving heart motion. Coronary imaging was conducted on eight volunteers based on retrospective gating to preliminarily validate the effectiveness of DP-RSG for whole-heart coronary MRA. Comparison of vessel delineation was performed between images reconstructed using different gating methods. Results:The quantitative evaluation shows that DP-RSG more accurately tracks heart motion than NAV with all gating window (GW) values and SP-RSG approaches with GW Ն2.5 mm and profile-matching algorithms are more reliable for motion derivation than center-of-mass calculations with GW Ն1.0 mm. Whole-heart coronary MRA studies demonstrate the feasibility of using DP-RSG to improve overall delineation of the coronary arteries.Conclusion: DP-RSG is a promising approach to better resolve respiratory motion for whole-heart coronary MRA compared to conventional NAV and SP-RSG. CORONARY MR ANGIOGRAPHY (MRA) is emerging as a noninvasive technique for diagnosis of coronary artery diseases. Conventionally, coronary MRA is performed using double-oblique thin slabs targeted at specific coronary artery branches and thus requires precise planning of the imaging plane for each coronary artery branch on each subject (1-3). Due to the tortuous geometry of coronary arteries, visualization is highly dependent on operator skills and ultimately restricted by the slab thickness. Lately, whole-heart coronary MRA was introduced to improve the ease-of-use and the length of vessel depiction (4,5). The complete coronary artery tree is covered in a single measurement and individual branches can be visualized by reformatting the three-dimensional dataset retrospectively. However, whole-heart scans require multifold increases in imaging time compared to volume-targeted scans. Despite recent significant advances in MRA, eg, fast pulse sequences and parallel imaging, the imaging time for high-quality whole-heart coronary MRA is still far beyond breath-hold capabilities and thus necessitates data acquisition during free-breathing.Free-breathing coronary MRA has been mostly relying on diaphragmatic navigator (NAV) approaches (4 -8). By tracking the motion of the right hemidiaphragmatic dome, respiratory motion of the heart along the superior-inferior (SI) direction can be estimated using an empirical correction factor (typically 0.6) and used for gating and slice tracking (9). NAV approaches are reliant on a simplified motion model a...

Z intensity-weighted position self-respiratory gating method for free-breathing 3D cardiac CINE imaging

“…Some techniques, therefore, have added one extra signal readout within each TR to sample the center of k-space only 4 . An alternative approach consists of periodically inserting specialized readouts into the SSFP signal train for which least squares or maximum correlation coefficients are then used to detect motion 23,24 . The ZIP method proposed here can detect the z-value of the center of mass without using extra projections, whose gradients may cause eddy current artifacts in SSFP.…”

Motion Compensation Strategies in Magnetic Resonance Imaging

“…In order to cope with this drawback, Lai et al 66 proposed using the least-squares error between the KCLs to extract the motion. In further work, the same group improved the suppression of background structures by also acquiring a second anterior-posterior projection (prior to high-spatial resolution data acquisition) from which they extracted the in-plane motion, 67 while they later extended this translation correction to the third dimension. 68 KCLs were also exploited in cine imaging to perform real-time respiratory self-gating for whole-heart cine MRI 69 and were filtered in real time to extract cardiac and a) b) respiratory patterns to perform fully gatingfree dynamic acquisitions.…”

Respiratory and cardiac self‐gated free‐breathing cardiac CINE imaging with multiecho 3D hybrid radial SSFP acquisition

“…Respiratory position may be measured by acquiring MR signal from internal organs undergoing respiratory motion such as the diaphragmatic navigator (NAV) (2, 3) and k ‐space centers (4–8), or by using the image data themselves (9, 10). Navigator gating often performs well for free‐breathing three‐dimensional (3D) coronary artery imaging, where data are acquired during a limited portion of cardiac cycle, but is not suited for cine SSFP imaging due to the interruption of the steady state.…”