Renske Merton^{1}, Eric M. Schrauben^{1}, Gustav J. Strijkers^{2}, Aart J. Nederveen^{1}, and Pim van Ooij^{1,3}

^{1}Radiology and Nuclear Medicine, Amsterdam University Medical Centers, Amsterdam, Netherlands, ^{2}Department of Medical Engineering & Physics, Amsterdam University Medical Centers, Amsterdam, Netherlands, ^{3}University Medical Center Utrecht, Utrecht, Netherlands

Capturing 3D aortic motion over the heart cycle may give insight into a new biomarker for aortic disease and potentially improve the measurement of aortic hemodynamic parameters. An isotropic, free-breathing, respiratory-corrected 3D CINE balanced steady-state free precession imaging technique of the thoracic aorta was developed to investigate scan-rescan reproducibility of aortic diameter and displacement measures in nine healthy volunteers. Scan-rescan diameter was highly reproducible (CV<10% , ICC=0.85-0.86 and Pearson’s ρ=0.87) while displacement was more variable (CV=34-42%, ICC=0.34-0.50, ρ=0.59-0.72). These results are encouraging for future studies investigating aortic motion in health and aortopathy.

CINE balanced steady-state free precession (bSSFP) provides excellent blood-tissue contrast to study motion of the heart and aorta, but is clinically acquired in multiple breath-holds and thick slices, hindering accurate quantification of 3D diameter and motion. Therefore, the aim of this study was to create an isotropic, free-breathing, respiratory-corrected 3D CINE bSSFP imaging technique of the thoracic aorta, and to investigate aortic scan-rescan reproducibility of diameter and displacement measurements.

For respiratory correction of PROUD CINE, the k

The segmentations were transformed into surface objects in Matlab and the diameter was calculated per surface vertex as the length of the vector along the normal of the surface to the opposing side

Diameter and displacement results are given as mean ± standard deviations. To quantify scan-rescan reproducibility of these metrics, the rescan data was rigidly registered and interpolated

For all diameter and displacement measurements, the absolute mean differences were smaller than 0.5 mm with LoA=2.5-3.5 mm. The reproducibility for diameter measurements was good (CV<10% , ICC=0.85 and ρ=0.87) while the reproducibility for voxel-by-voxel displacement was poor (CV=42%, ICC=0.34, ρ=0.59). Displacement reproducibility was higher for the ascending aorta (CV=34%, ICC=0.50, ρ=0.72).

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*Figure 1: Data acquisition and reconstruction pipeline 1. A free-running prospectively undersampling bSSFP acquires data in ~4 minutes. 2. From the k*

*Figure 2: Reconstruction of PROUD CINE with segmentation contour of diastolic (blue) and end-systolic phase (red) of the scan and rescan in one volunteer in coronal, axial and sagittal view.*

*Figure 3: Post processing pipeline 1. The systolic and diastolic aorta segmentations are transformed to a surface in Matlab. 2. For each surface vertex the diameter is calculated. For the final analysis a fixed extend of the surfaces are discarded to remove erroneous diameter calculations from face-end vertices. 3. The systolic surface is non-rigidly registered to the diastolic surface using iterative closest point method and diameter values interpolated.*

*Figure 4: Scan-rescan diameter and displacement analysis in one volunteer of diastolic diameter (a) systolic diameter (b) and displacement (c). 1: The 3D diameter and displacement fields used for the voxel-by-voxel analysis. 2: voxel-by-voxel analysis: Bland-Altman comparison, 3: orthogonal regression.*

DOI: https://doi.org/10.58530/2022/1229