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Free-breathing 3D whole-heart coronary mra using respiratory motion-resolved sparse reconstruction
Journal of Cardiovascular Magnetic Resonance volume 18, Article number: O105 (2016)
Navigator gating is commonly used to minimize respiratory motion in free-breathing whole-heart coronary MRA . However, lengthy and unpredictable acquisition times remain a drawback. Respiratory self-navigation (SN) [2-3], conversely, enables 100% scan efficiency, but performs motion correction over a broad range of respiratory displacements, which can result in image artifacts. Here, we propose an alternative respiratory motion-resolved approach based on 3D radial phyllotaxis sampling, respiratory motion sorting and sparse reconstruction.
Examinations in N = 11 healthy volunteers (9 male, age: 29 ± 4 y) were performed on a 1.5T clinical MRI scanner (MAGNETOM Aera, Siemens Healthcare) with a prototype 3D radial phyllotaxis bSSFP sequence : TR/TE 3.1/1.56 ms, FOV (220 mm)3, matrix 1923, voxel (1.15 mm)3, RF angle 115°, and receiver BW 898 Hz/Px. Using a respiratory signal directly extracted from the modulations of the k-space center amplitude within the radial imaging data , signal-readouts were grouped according to the respiratory state at which they were acquired (Fig. 1). The resulting series of undersampled respiratory states were reconstructed using an eXtra-Dimensional Golden-angle RAdial Sparse Parallel imaging (XD-GRASP)  algorithm, which exploits sparsity along the newly created respiratory dimension. Datasets for 4 respiratory states were reconstructed. Image quality of the end-expiratory phase was compared to 1D respiratory self-navigation in terms of vessel sharpness (VS) , visible length (VL) and diagnostic quality on a scale from 0 (non-visible) to 2 (diagnostic).
Respiratory-resolved XD-GRASP reconstruction effectively suppresses respiratory motion artifacts (Fig. 1). Average VS and VL were always superior for the respiratory-resolved datasets, reaching statistical significance (p < 0.05) for the left main (LM), for the proximal and mid left anterior descending artery (LAD) (e.g. VS of mid LAD 40.8 ± 9.1% vs 34.9 ± 10.2%) and for the mid right coronary artery (RCA). Visualized length of LM+LAD was significantly increased as well. A total of 41/88 coronary segments were graded as diagnostic for 1D SN, while this ratio increased to 61/88 for the XD-GRASP reconstruction (Tab.1). The XD-GRASP reconstruction reached 100% diagnostic quality for LM, proximal-LAD, and proximal-RCA.
Instead of discarding data or enforcing motion models for motion correction, XD-GRASP makes constructive use of all respiratory phases to improve image quality, and achieves superior quality compared to 1D respiratory SN without the need for breath-holding, navigators, or complex 3D respiratory motion correction schemes. The phyllotaxis trajectory and XD-GRASP reconstruction provide a synergistic combination that may lead routine coronary MRA closer to clinical practice.
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Piccini, D., Feng, L., Bonanno, G. et al. Free-breathing 3D whole-heart coronary mra using respiratory motion-resolved sparse reconstruction. J Cardiovasc Magn Reson 18, O105 (2016). https://doi.org/10.1186/1532-429X-18-S1-O105
- Left Anterior Descend
- Right Coronary Artery
- Respiratory Motion
- Left Main
- Sparse Reconstruction