Monitoring carotid arterial stiffness using non-contrast-enhanced 4D MR angiography

OBJECTIVE: The anatomy of carotid arteries is evaluated with magnetic resonance angiography (MRA), while its stiffness-related parameters are evaluated using ultrasound. An isotropic three-dimensional (3D) MRA technique enabling the measurement of diameter changes could provide a dynamic assessment of the entire carotid tree, extending the existing clinical carotid MR toolset. The goal of this feasibility study was to comprehensively characterize stiffness-related parameters with dynamic 3D MRA and evaluate its repeatability compared to ultrasound. MATERIALS AND METHODS: A non-contrast-enhanced free-running 3D radial MRA sequence was used in 18 healthy volunteers (9 males, 9 females, aged 49 ± 20 years, mean ± standard deviation), scanned twice with both MRA and ultrasound. Diameter changes throughout the cardiac cycle were measured in MRA and ultrasound images to compute stiffness-related parameters: systolic-diastolic relative diameter change (RDC), stiffness index, arterial compliance (AC), local pulse wave velocity and pressure-strain Young's elastic modulus (E), computed for the left (LC) and right (RC) common carotid arteries. Repeatability was evaluated for systolic and diastolic diameter measurements using the intraclass correlation coefficient (ICC). Sub-analyses were performed on a junior and senior subgroup of the volunteers. RESULTS: When evaluating MRA versus ultrasound differences, a relative MRA overestimation of the RDC in the senior cohort (p < 0.001) led to higher AC (p = 0.010) and E (p = 0.042). All stiffness-related parameters were significantly different between the age cohorts. MRA showed high repeatability for the LC (ICC = 0.95) and RC (ICC = 0.93) compared to ultrasound (ICC = 0.78, ICC = 0.51, respectively). CONCLUSION: Carotid stiffness can be repeatably quantified with non-contrast-enhanced 4D MRA, providing information traditionally obtained with ultrasound. RELEVANCE STATEMENT: Dynamic free-running non-contrast-enhanced MRA allows the noninvasive quantification of carotid dynamic properties and anatomy, demonstrating its potential for the assessment of 3D vascular age, showing superior repeatability compared to the clinical standard ultrasound. KEY POINTS: Carotid stiffness is assessed with ultrasound and anatomy with MR imaging; combining both assessments in an examination would be valuable. Carotid stiffness can be repeatably quantified with free-running non-contrast-enhanced MRA and yields metrics comparable to ultrasound in healthy volunteers. Dynamic 3D MRA may enable the measurement of stiffness parameters throughout the carotid tree.