Repspiratory motion correction with a 2d self-navigator from bssfp dummy profiles
Journal of Cardiovascular Magnetic Resonance volume 13, Article number: P229 (2011)
Several self-navigation techniques have been proposed to improve respiratory motion compensation in CMRA. Motion estimation is, however, often impeded by static structures within the excited volume. In this work a 2D self-navigation (2DSN) method is proposed and implemented by using the dummy profiles of a 3D bSSFP sequence. To create 2DSN images we added phase encoding (PE) gradients during the start-up echoes. With this approach we can calculate foot-head motion and retrospectively perform translational correction.
The objective of the study was to investigate the feasibility of respiratory motion correction using a novel self-navigation method and comparing it to a diaphragmatic 1D navigator (1Dnav).
Material and methods
The proposed sequence is shown in Figure 1 where the number of dummy profiles corresponds to the 2DSN resolution in PE direction. No PE was performed in slice selection direction and the SNI are projections of the field-of-view in this direction. The 3D bSSFP imaging parameters included field-of-view=200x200x100mm, resolution=1x1x1mm, TE/TR=5.0/2.5ms, FA=70°. Ten profiles were acquired in each shot to create a 2DSN image with a resolution of 1x6x100mm. A template matching algorithm was used to extract motion from a region-of-interest, shown in Figure 2. A diaphragmatic 1Dnav was used for respiratory gating (10mm), and the 1Dnav values were also used for retrospective correction using a tracking factor of 0.6. Additionally, the data was reconstructed without motion correction. Two healthy volunteers were scanned on a Philips 1.5T Achieva scanner (Philips Healthcare, Best, NL) with the imaging plane in the sagittal orientation with PE in anterior-posterior direction and read-out in foot-head direction.
Discussion and conclusion
The initial results in volunteers with the proposed self-navigation method are very promising as it provides a model-free motion correction method, which comes at no “expense” as the navigator is extracted from the dummy profiles used for magnetization preparation. Compared to other self-gating methods the main advantage of the proposed approach is that a spatial separation of the moving heart and static structures is possible. Future work will explore the use of motion correction with more degrees of freedom, e.g. affine motion, which is possible since the self-navigating method spatially encodes in 2D.
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Cite this article
Henningsson, M., Koken, P., Stehning, C. et al. Repspiratory motion correction with a 2d self-navigator from bssfp dummy profiles. J Cardiovasc Magn Reson 13 (Suppl 1), P229 (2011). https://doi.org/10.1186/1532-429X-13-S1-P229