Highly efficient respiratory gating in coronary MR employing non-rigid retrospective motion correction
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BioMed Central
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Highly efficient respiratory gating in coronary MR employing non-rigid retrospective motion correction Johannes F Schmidt*, Martin Buehrer, Peter Boesiger and Sebastian Kozerke Address: Institute of Biomedical Engineering, University and ETH Zürich, Zurich, Switzerland * Corresponding author
from 13th Annual SCMR Scientific Sessions Phoenix, AZ, USA. 21-24 January 2010 Published: 21 January 2010 Journal of Cardiovascular Magnetic Resonance 2010, 12(Suppl 1):P41
doi:10.1186/1532-429X-12-S1-P41
Abstracts of the 13th Annual SCMR Scientific Sessions - 2010
Meeting abstracts - A single PDF containing all abstracts in this Supplement is available here. http://www.biomedcentral.com/content/files/pdf/1532-429X-11-S1-infoThis abstract is available from: http://jcmr-online.com/content/12/S1/P41 © 2010 Schmidt et al; licensee BioMed Central Ltd.
Introduction Three-dimensional whole heart imaging becomes the method of choice in cardiac applications [1] as it avoids extensive planning of imaging slices and allows reconstructing arbitrary slice orientations. The drawback is a relatively long scan time on the order of several minutes which requires motion compensation to suppress motion artifacts. Prospective techniques such as respiratory navigator based gating or triggering including slice tracking is often used. Recently, retrospective approaches were successfully implemented by extending the image encoding matrix with motion operators and solving the system iteratively [2-4]. This allows for increased gating windows or even continuous scanning across the entire breathing cycle but necessitates detailed information of the underlying motion vector field at each acquisition.
tion [5]. Missing respiratory states were linearly interpolated. The actual 3D scan was a standard navigator-gated 3D-BTFE sequence with an increased gating window of 20 mm and a voxel size of 1.33 × 1.33 × 1.33 mm3. An additional 3D scan with a gating window of 5 mm was acquired as reference. Before reconstruction, the coil array was combined to one virtual coil to reduce the data set [6]. The extended encod-
Purpose In this work, a template-based approach for retrospective motion correction was used to correct for respiratory motion artifacts in free-breathing coronary MR scans with gating windows as large as 20 mm.
Methods Whole heart images were acquired in six healthy subjects on a 1.5 T Philips Achieva System (Philips Healthcare, Best, The Netherlands). A volunteer-specific motion model was retrieved from a low-resolution multi-2D prescan with a voxel size of 4 × 4 × 4 mm3, where each slice was acquired repeatedly in single-shot mode at different respiratory states. The motion vector fields between these respiratory states were then calculated by image registra-
Figure The as matrix effect 1 equation of motion during a multi-shot scan can be written The effect of motion during a multi-shot scan can be written as matrix equation. TI are motion operators which describe the motion per vo
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