Aortic length measurements for pulse wave velocity calculation: manual 2D vs automated 3D centreline extraction

Abstract

BackgroundPulse wave velocity (PWV) is a biomarker for the intrinsic stiffness of the aortic wall, and has been shown to be predictive for cardiovascular events. It can be assessed using cardiovascular magnetic resonance (CMR) from the delay between phase-contrast flow waveforms at two or more locations in the aorta, and the distance on CMR images between those locations. This study aimed to investigate the impact of different distance measurement methods on PWV. We present and evaluate an algorithm for automated centreline tracking in 3D images, and compare PWV calculations using distances derived from 3D images to those obtained from a conventional 2D oblique-sagittal image of the aorta.MethodsWe included 35 patients from a twin cohort, and 20 post-coarctation repair patients. Phase-contrast flow was acquired in the ascending, descending and diaphragmatic aorta. A 3D centreline tracking algorithm is presented and evaluated on a subset of 30 subjects, on three CMR sequences: balanced steady-state free precession (SSFP), black-blood double inversion recovery turbo spin echo, and contrast-enhanced CMR angiography. Aortic lengths are subsequently compared between measurements from a 2D oblique-sagittal plane, and a 3D geometry.ResultsThe error in length of automated 3D centreline tracking compared with manual annotations ranged from 2.4 [1.8-4.3] mm (mean [IQR], black-blood) to 6.4 [4.7-8.9] mm (SSFP). The impact on PWV was below 0.5m/s (<5%). Differences between 2D and 3D centreline length were significant for the majority of our experiments (p < 0.05). Individual differences in PWV were larger than 0.5m/s in 15% of all cases (thoracic aorta) and 37% when studying the aortic arch only. Finally, the difference between end-diastolic and end-systolic 2D centreline lengths was statistically significant (p < 0.01), but resulted in small differences in PWV (0.08 [0.04 - 0.10]m/s).ConclusionsAutomatic aortic centreline tracking in three commonly used CMR sequences is possible with good accuracy. The 3D length obtained from such sequences can differ considerably from lengths obtained from a 2D oblique-sagittal plane, depending on aortic curvature, adequate planning of the oblique-sagittal plane, and patient motion between acquisitions. For accurate PWV measurements we recommend using 3D centrelines.

3D aortic morphology and stiffness in MRI using semi-automated cylindrical active surface provides optimized description of the vascular effects of aging and hypertension

“…Regarding the aortic arch length, our results were in line with those of a previous work [28] which compared 2D and 3D measurements and reported length differences <10mm that induced small variations in PWV MRI (< 0.5m.s -1 ), although smaller differences were found in our study (differences in length <3mm and PWV <0.25m/s). This may be explained by the fact that in our 2D manual aortic centerline delineation strategy, a stack of axial views was used in addition to the 2D sagittal oblique view as reported in [28], to better account for aortic tortuosity [9]. However, even this multi-slice tracing strategy could not fully capture the local tortuosity as revealed by the BA plot (Figure 4.a),…”

Quantification of aortic pulse wave velocity from a population based cohort: a fully automatic method

“…The multi-slice 3D scan protocol used in our study was optimized to shorten the duration of the scan time which often leads to poor signal-to-noise ratio and also the image resolution is inferior when compared to the volumetric protocol used in the study of van Engelen et al Hence using a vesselness filter to preprocess our data would not give a good filter response. Moreover, comparing the results obtained by van Engelen et al [42] on the 3D volumetric scan protocol shows that they achieved an absolute centerline length error of 4.8 mm, whereas our fully automatic method results in a much smaller error of 3.3 mm. The method of Babin et al [43] uses graph paths with intensity related information and Dijkstra’s shortest path [32] to extract the centerline.…”

“…The method presented by van Engelen et al [42] also extracts the aorta length in 3D, by using a scan protocol for volumetric acquisition. Their method is based on a vesselness filter [40] and a minimum-cost path [41] approach to extract the centerline.…”

Cerebrospinal fluid pulse wave velocity measurements: In vitro and in vivo evaluation of a novel multiband cine phase‐contrast MRI sequence

“…As found by van Engelen et al, inaccuracies of manual distance measurements for the estimation of the PWV along the aortic arch based on a sagittal 2D plane were below 10 mm. 35 In this study, a slice distance of 180 mm was used, which conforms to deviations under 5.5% with uncertainties below 10 mm. Although differences between the average of both sessions of the in vivo measurements were not significant and deviations of slice distances between session 1 and 2 were low, automatic distance measurements, such as using 3D centerline extraction, may further improve the accuracy of CSF-PWV measurements.…”