Computation of aortic pressure fields from 4D flow MRI

MOUSSEAUX, E; SOULAT G; BARGIOTAS I; KACHENOURA N; CRAIEM D; GENCER U; DIETENBECK T; BOLLACHE E; BOUAOU K

Conferencia; SCMR 22nd Annual Scientific Sessions; 2019

SCMR

BackgroundAlthough MRI aortic pressure mapping has been illustrated in patients with pronounced aortic geometrical changes, age-related subclinical spatio-temporal pressure variations have not been explored. We aimed to compute aortic time-dependent pressure fields in healthy subjects from 4D flow MRI using Navier-Stokes equations and to define relevant pressure-based markers while investigating: 1) their relationship with age and 2) their sensitivity to temporal resolution.MethodsWe studied 47 healthy subjects (age: 49.5±18years, 24 women) who underwent aortic 4D flow MRI. Spatio-temporal pressure fields (Figure) were computed by spatially integrating pressure gradients obtained from velocity fields using Navier-Stokes equations, while assuming zero pressure at the sino-tubular junction. In order to assess pressure spatio-temporal variations, we calculated: 1) volumetric aortic pressure gradients ΔPE1 / ΔV and ΔPE2 / ΔV, representing slopes of early (PE1) and late (PE2) systolic relative pressure peaks respectively (Figure), according to the cumulated aortic volume throughout the entire aorta, 2) ∆AE1-E2defined as the absolute difference between early and late systolic relative pressure peaks amplitude. The effect of temporal resolution was also studied in a subgroup of 20 subjects with 20 and 50 time-phase reconstructions.ResultsSpatio-temporal variations of 4D flow MRI-derived aortic pressure peaks decreased significantly with age (Table 1), in terms of absolute magnitude: ΔPE1 / ΔV (r=0.70, p<0.005), ΔPE2 / ΔV  (r=-0.45, p<0.005) and ∆AE1-E2 (r=-0.45, p<0.005). Averaged changes of 43%, 35%, and 23% was found for ΔPE1 / ΔV, ΔPE2 / ΔV and ∆AE1-E2 between subjects E1 / ΔV, ΔPE2 / ΔV and ∆AE1-E2, respectively (Table 2).Conclusion4D flow MRI relative aortic pressures were consistent with physiological knowledge as demonstrated by their volumetric and temporal variations with age. Although significant, the effect of temporal resolution was on average less important than aging effect.