Several self-navigation techniques have been proposed to improve respiratory motion compensation in coronary MR angiography. In this work, we implemented a 2D self-navigation method by using the startup profiles of a whole-heart balanced Steady-state free precession sequence, which are primarily used to catalyze the magnetization towards the steady-state. To create 2D self-navigation images (2DSN), we added phase encoding gradients to the startup profiles. With this approach we calculated foot-head and left-right motion and performed retrospective translational motion correction. The 2DSN images were reconstructed from 10 startup profiles acquired at the beginning of each shot. Nine healthy subjects were scanned, and the proposed method was compared to a 1D self-navigation (1DSN) method with foot-head correction only. Foot-head correction was also performed with the diaphragmatic 1D pencil beam navigator (1Dnav) using a tracking factor of 0.6. 2DSN shows improved motion correction compared to 1DSN and 1Dnav for all coronary arteries and all subjects for the investigated diaphragmatic gating window of 10 mm. The visualized vessel length of the right coronary artery could be significantly improved with a multiple targeted 2D self-navigation approach, compared to 2DSN method. Magn Reson Med 67:437-445, 2012. V C 2011 Wiley Periodicals, Inc.Key words: respiratory motion correction; whole-heart CMRA; 2D self-navigation Despite ongoing advances in MR sequence development respiratory motion remains a major impediment in coronary MR angiography (CMRA) (1). Early motion correction work focused on diaphragmatic 1D navigators (2), whereby motion models of different complexity, from foot-head (FH) translation (3) to affine 3D models (4), were used to relate diaphragmatic to cardiac motion. Recently, several self-navigation techniques have been proposed to improve respiratory motion correction and improve ease of use in CMRA (5-7). Compared to diaphragmatic navigators self-navigation methods do not require the use of a heart-diaphragm motion model, as they allow direct measurement of respiration-induced bulk cardiac motion. The direct measurement of cardiac motion also circumvents the problem of hysteresis between diaphragmatic and heart motion (8). The previously mentioned self-navigation approaches measure motion from 1D projections in one or more directions which means that motion could be impeded by static structures within the excited volume (9). Image based approaches have been proposed to improve motion estimation, by spatially encoding in 2D (10-12) or 3D (13), which allows for separation of the static chest wall and the moving heart. In this work, we create 2D self-navigation (2DSN) images by encoding the startup profiles of a balanced steady-state free precession sequence, similar to Yui et al. (12), which are primarily used to catalyze the magnetization towards the steady-state. This allows for spatial separation of static and moving structures, as well as translational correction in frequency and the phase encodi...

Purpose: To develop an efficient 3D affine respiratory motion compensation framework for Cartesian wholeheart coronary magnetic resonance angiography (MRA). Materials and Methods:The proposed method achieves 100% scan efficiency by estimating the affine respiratory motion from the data itself and correcting the acquired data in the reconstruction process. For this, a golden-step Cartesian sampling with spiral profile ordering was performed to enable reconstruction of respiratory resolved images at any breathing position and with different respiratory window size. Affine motion parameters were estimated from image-based registration of 3D undersampled respiratory resolved images reconstructed with iterative SENSE and motion correction was performed directly in the reconstruction using a multiple-coils generalized matrix formulation method. This approach was tested on healthy volunteers and compared against a conventional diaphragmatic navigator-gated acquisition using quantitative and qualitative image quality assessment. Results:The proposed approach achieved 47 6 12% and 59 6 6% vessel sharpness for the right (RCA) and left (LAD) coronary arteries, respectively. Also, good quality visual scores of 2.4 6 0.74 and 2.44 6 0.86 were observed for the RCA and LAD (scores from 0, no to 4, excellent coronary vessel delineation). A not statically significant difference (P ¼ 0.05) was found between the proposed method and an 8-mm navigator-gated and tracked scan, although scan efficiency increased from 61 6 10% to 100%. Conclusion:We demonstrate the feasibility of a new 3D affine respiratory motion correction technique for Cartesian whole-heart CMRA that achieves 100% scan efficiency and therefore a predictable acquisition time. This approach yields image quality comparable to that of an 8-mm navigator-gated acquisition with lower scan efficiency. Further evaluation of this technique in patients is now warranted to determine its clinical use.

Compressed sensing (CS) has been demonstrated to accelerate MRI acquisitions by reconstructing sparse images of good quality from highly undersampled data. Motion during MR scans can cause inconsistencies in k-space data, resulting in strong motion artifacts in the reconstructed images. For CS to be useful in these applications, motion correction techniques need to be combined with the undersampled reconstruction. Recently, joint motion correction and CS approaches have been proposed to partially correct for effects of motion. However, the main limitation of these approaches is that they can only correct for affine deformations. In this work, we propose a novel motion corrected CS framework for free-breathing dynamic cardiac MRI that incorporates a general motion correction formulation directly into the CS reconstruction. This framework can correct for arbitrary affine or nonrigid motion in the CS reconstructed cardiac images, while simultaneously benefiting from highly accelerated MR acquisition. The application of this approach is demonstrated both in simulations and in vivo data for 2D respiratory self-gated free-breathing cardiac CINE MRI, using a golden angle radial acquisition. Results show that this approach allows for the reconstruction of respiratory motion corrected cardiac CINE images with similar quality to breath-held acquisitions. Magn Reson Med 70:504-516, 2013. V C 2012 Wiley Periodicals, Inc.