Markus Henningsson

Whole-heart coronary MR angiography with 2D self-navigated image reconstruction

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, 2012.

Highly efficient respiratory motion compensated free-breathing coronary mra using golden-step Cartesian acquisition

To develop an efficient 3D affine respiratory motion compensation framework for Cartesian whole‐heart coronary magnetic resonance angiography (MRA).

Whole‐Heart Coronary MRA with 3D Affine Motion Correction Using 3D Image‐Based Navigation

Robust motion correction is necessary to minimize respiratory motion artefacts in coronary MR angiography (CMRA). The state‐of‐the‐art method uses a 1D feet‐head translational motion correction approach, and data acquisition is limited to a small window in the respiratory cycle, which prolongs the scan by a factor of 2–3. The purpose of this work was to implement 3D affine motion correction for Cartesian whole‐heart CMRA using a 3D navigator (3D‐NAV) to allow for data acquisition throughout the whole respiratory cycle.

Prospective respiratory motion correction for coronary MR angiography using a 2D image navigator.

Respiratory motion remains the major impediment in a substantial amount of patients undergoing coronary magnetic resonance angiography. Motion correction in coronary magnetic resonance angiography is typically performed with a diaphragmatic 1D navigator (1Dnav) assuming a constant linear relationship between diaphragmatic and cardiac respiratory motion. In this work, a novel 2D navigator (2Dnav) is proposed, which prospectively corrects for translational motion in foot–head and left–right direction. First, 1Dnav‐ and 2Dnav‐based motion correction are compared in 2D real time imaging experiments, by evaluating the residual respiratory motion in 10 healthy subjects as well as in a moving vessel phantom. Subsequently, 1Dnav and 2Dnav corrected high‐resolution 3D coronary MR angiograms were acquired, and both objective and subjective image quality were assessed. For a gating window of 10 mm, 1Dnav and 2Dnav performed equally well; however, without any respiratory gating, the 1Dnav had a lower visual score for all coronary arteries compared with 10 mm gating, whereas the 2Dnav without gating performed similar to 1Dnav with 10 mm gating. Magn Reson Med, 2013.

100% Efficient Three-Dimensional Coronary MR Angiography with Two-Dimensional Beat-to-Beat Translational and Bin-to-Bin Affine Motion Correction

To develop a flexible image navigator for 3D coronary MR angiography that allows respiratory motion of variable complexity to be compensated for on different temporal scales.

Advanced Respiratory Motion Compensation for Coronary MR Angiography

Despite technical advances, respiratory motion remains a major impediment in a substantial amount of patients undergoing coronary magnetic resonance angiography (CMRA). Traditionally, respiratory motion compensation has been performed with a one-dimensional respiratory navigator positioned on the right hemi-diaphragm, using a motion model to estimate and correct for the bulk respiratory motion of the heart. Recent technical advancements has allowed for direct respiratory motion estimation of the heart, with improved motion compensation performance. Some of these new methods, particularly using image-based navigators or respiratory binning, allow for more advanced motion correction which enables CMRA data acquisition throughout most or all of the respiratory cycle, thereby significantly reducing scan time. This review describes the three components typically involved in most motion compensation strategies for CMRA, including respiratory motion estimation, gating and correction, and how these processes can be utilized to perform advanced respiratory motion compensation.

Characterization of Coronary Atherosclerosis by Magnetic Resonance Imaging

Coronary atherosclerosis remains the major cause of mortality in industrialized and developing nations.1 Clinical risk-scoring systems do not allow satisfactory identification of individuals with subclinical disease and at high risk for coronary events.2 Novel approaches to more reliably identify asymptomatic individuals at high risk for future cardiovascular events are therefore urgently needed. Subclinical atherosclerosis may precede the development of clinical disease by many decades, thereby offering the opportunity to target primary prevention therapies to those at highest risk.3 Because of its noninvasiveness, excellent soft-tissue contrast, and ability to visualize blood and the coronary vessel wall with and without contrast agents, magnetic resonance (MR) imaging (MRI) is a very promising imaging modality to assess coronary lumen integrity, plaque burden, and biological plaque composition. Studies investigating subclinical and clinical coronary atherosclerosis have included non–contrast-enhanced (NCE) and contrast-enhanced (CE) coronary vessel wall cardiovascular MR (CMR). Recent studies have shown that noninvasive MR angiography allows the assessment of the presence or absence of >50% coronary artery stenosis with a diagnostic accuracy comparable to that of multidetector computer tomography if performed in a head-to-head comparison and with similar pharmacological preparation.4,5 Technical improvements in coil design, image acquisition and reconstruction, and motion compensation have allowed shortening the total imaging time of whole-heart coronary MR angiography to ≈5 minutes while maintaining good diagnostic accuracy.6–8 Several single-center and multicenter trials have demonstrated the potential of this technique compared with both x-ray coronary angiography and multidetector computer tomography.4,9,10 Direct assessment of the coronary vessel wall thickness and remodeling has been demonstrated with NCE-CMR in patients with subclinical coronary artery disease, in patients with type 1 diabetes mellitus, and in a multiethnic population (Multi-Ethnic Study of Atherosclerosis [MESA]) cohort.11–13 Additionally, NCE-CMR has been …

A new framework for interleaved scanning in cardiovascular MR: Application to image-based respiratory motion correction in coronary MR angiography.

To describe a new framework for interleaving scans and demonstrate its usefulness for image‐based respiratory motion correction in whole heart coronary MR angiography (CMRA).

Highly efficient nonrigid motion-corrected 3D whole-heart coronary vessel wall imaging

To develop a respiratory motion correction framework to accelerate free‐breathing three‐dimensional (3D) whole‐heart coronary lumen and coronary vessel wall MRI.

A new framework for interleaved scanning in cardiovascular MR

To describe a new framework for interleaving scans and demonstrate its usefulness for image‐based respiratory motion correction in whole heart coronary MR angiography (CMRA).