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Comparison of respiratory navigator techniques for interleaved high-resolution coronary vessel wall imaging
Journal of Cardiovascular Magnetic Resonance volume 15, Article number: E20 (2013)
Three-dimensional high-resolution PSIR LGE , flow-independent vessel wall imaging , or T1 mapping  are all implemented with interleaved sequences, where the same volume is imaged multiple times with different inherent contrast. These volumes are then processed together to generate additional information, e.g. recovering the sign of magnetization, depicting vessel walls via subtraction, or calculating T1 maps via curve-fitting. Such techniques rely on correct registration of the voxels, hence on accurate motion compensation. In this study, we sought to explore the effects of synchronous and asynchronous navigator gating and tracking on respiratory motion compensation in high-resolution coronary vessel wall imaging with an interleaved T2prep sequence (i-T2prep).
The right coronary artery (RCA) of 7 subjects (29.6±12.6 yrs) were imaged on a 1.5T Philips Achieva magnet with a targeted i-T2prep sequence using an interleaved SSFP acquisition (TR/TE/α=4.3/2.1 ms/90°, resolution=1×1×3 mm3, FOV=270×270×30 mm3) where one heartbeat (interleaf 1) was acquired with T2prep prepulse, and the subsequent one (interleaf 2) without . A 5 mm gating window was used with the following strategies: 1) Accept the data only if both interleaves are within the gating window (synchronous), 2) Accept each interleaf independently (asynchronous). Acquisition time for each scan was recorded. Coronary vessel wall images were generated by weighted subtraction of the two interleaves , and quantitative vessel sharpness measurements were performed on these vessel wall images.
Figure 1 shows reformatted RCA images with T2prep(+) and vessel wall images from a healthy subject. Both navigating techniques provide similar image quality, but the asynchronous scheme is shorter (8:03 vs. 11:58 mins). Figure 2 shows reformatted RCA images from another volunteer. The synchronous scheme has superior image quality, but also a longer acquisition time (20:31 vs. 8:15 mins). The synchronous scheme provides significantly better delineated vessel walls in terms of vessel sharpness (0.15±0.02 vs. 0.13±0.02, P=0.03) although the absolute difference is small. However, the asynchronous scheme is significantly shorter (9:29±1:35 vs. 18:18±6:21 mins, P=0.005).
We have investigated two navigating approaches for high-resolution interleaved sequences. Examples and quantitative data show that while the asynchronous scheme allows a significantly shorter scan time, independently accepting data from interleaves results in loss of image quality and sharpness, even though a 5 mm gating window is utilized. Techniques that require voxel-by-voxel processing of images from multiple interleaves may require motion correction within the gating window if a synchronous scheme cannot be utilized due to a higher number of interleaves.
NIH:K99HL111410-01;R01EB008743-01A2; BHF: RG/12/1/29262
Kellman : . MRM. 2003
Andia : . MRM. 2012
Mehta : . JCMR. 2012
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Akcakaya, M., Henningsson, M., Nezafat, R. et al. Comparison of respiratory navigator techniques for interleaved high-resolution coronary vessel wall imaging. J Cardiovasc Magn Reson 15, E20 (2013). https://doi.org/10.1186/1532-429X-15-S1-E20
- Right Coronary Artery
- Motion Compensation
- Vessel Wall Image
- Coronary Vessel Wall
- Sharpness Measurement