Variability of MRI Aortic Stiffness Measurements in a Multicenter Clinical Trial Setting: Intraobserver, Interobserver, and Intracenter Variability of Pulse Wave Velocity and Aortic Strain Measurement

Abstract

Purpose: To assess intraobserver, interobserver, and scan-rescan variability of MRI aortic stiffness measurements in a multicenter trial setting.

Materials and methods: This study was a retrospective analysis of prospectively collected data in a multicenter prospective clinical trial (clinicaltrials.gov ID NCT01870739). Forty-five adult patients (31 men; mean age, 58 years ± 12 [standard deviation]; 15 patients per center; three centers) with arterial hypertension underwent standardized 3-T baseline MRI assessments between June and September 2014. Aortic strain was calculated from maximum and minimum aortic area measurements repeated three times by three readers at three aortic levels on three retrospectively gated axial gradient-echo (GRE) data sets. Pulse wave velocity (PWV) was assessed three times by five readers as Δx/Δt: Δx was measured on a parasagittal GRE image of the aortic arch, and Δt was extracted from ascending and descending aortic velocity curves created on three axial phase-contrast acquisitions. Intraobserver, interobserver, and scan-rescan variability was calculated using percentage coefficient of variation (COV).

Results: Aortic strain variability was lowest at the level of the distal descending aorta (DDA) with median COVs of 1.6% for intraobserver variability, 4.0% for interobserver variability, and 10.3% for scan-rescan variability. It was highest at the ascending aorta (AA) with COVs of 3.6% for intraobserver variability, 10.7% for interobserver variability, and 19.8% for scan-rescan variability. Variability of PWV was low: 0.7% for intraobserver variability, 1.5% for interobserver variability, and 8.1% for scan-rescan variability.

Conclusion: Low variability can be achieved for aortic strain and PWV measurements in a multicenter trial setting using standardized MRI protocols. Although COV was lower when measuring aortic strain at DDA compared with AA, variability was acceptable at both anatomic locations.Supplemental material is available for this article.© RSNA, 2020.

Conflict of interest statement

Disclosures of Conflicts of Interest: M.H.P. disclosed no relevant relationships. A.K. disclosed no relevant relationships. S.A.S. disclosed no relevant relationships. S.K. disclosed no relevant relationships. F.S. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: employed by University Hospital Basel; institution receives grants from Swiss National Science Foundation and Swiss Foundation for the Research on Muscle Diseases; author receives travel accommodations from ESMRMB. Other relationships: disclosed no relevant relationships. R.E.S. disclosed no relevant relationships. N.K. disclosed no relevant relationships. D.Y. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: employed by Novartis Institutes of Biomedical Research which sponsored the clinical trial during which the aortic MRI data were acquired. Other relationships: disclosed no relevant relationships. T.L. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: employed by and has stock in Novartis Pharma. Other relationships: disclosed no relevant relationships. J.B. Activities related to the present article: disclosed no relevant relationships. Activities not related to the present article: disclosed no relevant relationships. Other relationships: University Hospital Basel was involved in a trial from Novartis and received funds for performing and analyzing MRI scans. The current analysis and manuscript, however, was done after the analysis for Novartis was completed. The current study used the image database, but otherwise is not related to the Novartis trial. T.H. disclosed no relevant relationships.

2020 by the Radiological Society of North America, Inc.

Figures

Figure 1:

Flow diagram of the standardized scanning protocol used for aortic stiffness assessment. AA = ascending aorta, DDA = distal descending aorta, GRE = gradient echo, PC = phase contrast, PDA = proximal descending aorta, PWV = peak wave velocity.

Figure 2a:

(a) Parasagittal (candy-cane) gradient-echo image depicting levels of aortic strain measurement: ascending and proximal descending aorta on the axial MR image at the level of the right pulmonary artery (white line) and the distal descending aorta at the level of the diaphragm (gray line). (b) Aortic lumen segmentation using ARTerial-FUNction software on 50 frames throughout the cardiac cycle.

Figure 2b:

(a) Parasagittal (candy-cane) gradient-echo image depicting levels of aortic strain measurement: ascending and proximal descending aorta on the axial MR image at the level of the right pulmonary artery (white line) and the distal descending aorta at the level of the diaphragm (gray line). (b) Aortic lumen segmentation using ARTerial-FUNction software on 50 frames throughout the cardiac cycle.

Figure 3a:

(a) Δx measurement on the parasagittal “candy-cane” gradient-echo MR image. The white line represents the reference plane of through-plane phase-contrast images. (b) Ascending (green) and descending (red) aortic mean velocity curves used to fit two normalized sigmoid curves to their systolic upslope to delimit minimized area between them for Δt calculation by transit time–upslope method.

Figure 3b:

(a) Δx measurement on the parasagittal “candy-cane” gradient-echo MR image. The white line represents the reference plane of through-plane phase-contrast images. (b) Ascending (green) and descending (red) aortic mean velocity curves used to fit two normalized sigmoid curves to their systolic upslope to delimit minimized area between them for Δt calculation by transit time–upslope method.

Figure 4:

Tukey box plots represent intraobserver, interobserver, and scan-rescan variability for aortic strain at the level of ascending aorta (AA), proximal descending aorta (PDA), and distal descending aorta (DDA) and for pulse-wave velocity (PWV). COV = coefficient of variation.