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High resolution, free-breathing coronary artery imaging with >99% respiratory efficiency
Journal of Cardiovascular Magnetic Resonance volume 12, Article number: P35 (2010)
High-resolution coronary artery acquisitions are generally gated to end-expiration using navigators and have intrinsically low respiratory efficiency (RE), which is exacerbated by respiratory drift. Alternatively, epicardial fat can be used as a marker of coronary artery position in a 3D beat-to-beat non-model based subject-specific respiratory motion correction (B2B-RMC) technique. We propose this technique can acquire high-resolution coronary artery images with approximately 100% RE.
In-plane right coronary images were acquired in 10 subjects on a Siemens 1.5 T Avanto scanner. For B2B-RMC, a 3D low resolution spiral dataset with fat selective excitation was acquired every cardiac cycle immediately before 2 interleaves of a 3D high-resolution spiral dataset with water selective excitation. A following navigator was used to reject data at extreme respiratory positions (>10 mm outside normal range). Beat-to-beat respiratory displacement of the coronary artery was determined from the low resolution images using localized 3D normalized sub-pixel cross-correlation of fat around the coronary origin (relative to end-expiration) and used to retrospectively correct the corresponding high-resolution interleaves. Navigator gated (5 mm window) 3D balanced steady-state free-precession (nav-bSSFP) with T2-prep and identical resolution to the B2B-RMC technique was chosen for comparison.
For each B2B-RMC and nav-bSSFP dataset, a maximum intensity projection was generated with anatomy overlying the artery nulled. Average vessel diameter (full-width half maximum) and sharpness (inverse of 20-80% intensity distance) were measured in the proximal (0-20 mm) and mid (20-40 mm) arteries.
The RE was 99.7% (range 98.4-100%) and 40.7%, (range 33.2-53.6%) for B2B-RMC and nav-bSSFP respectively (paired t-test p < 0.0001). There was no significant difference in proximal or mid sharpness between the two methods (table 1), no significant difference between methods for mid diameters and a significant but insubstantial (0.15 mm) difference in proximal diameter which is possibly due to reduced vessel wall signal in the T2-prepared nav-bSSFP technique. Figure 1 shows B2B-RMC images optimally corrected for the proximal(a) and distal(b) vessel (RE = 99.3%) and the equivalent nav-bSSFP results(c) (RE = 41.0%).
High-resolution coronary artery images were acquired with 99.7% RE using B2B-RMC in 10 subjects. Diameter and sharpness in the proximal and mid vessel were not substantially different to values obtained with nav-bSSFP acquired with mean RE 40.7%. For optimal visualisation, the B2B-RMC method requires cross-correlation of a local region of fat, as demonstrated in (a) and (b). Further work will merge images corrected for both proximal and distal vessel motion to generate a single corrected dataset.
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Scott, A.D., Keegan, J. & Firmin, D.N. High resolution, free-breathing coronary artery imaging with >99% respiratory efficiency. J Cardiovasc Magn Reson 12 (Suppl 1), P35 (2010). https://doi.org/10.1186/1532-429X-12-S1-P35
- Selective Excitation
- Respiratory Efficiency
- Corrected Dataset
- Respiratory Motion Correction
- Respiratory Position