Estimation of the differential pressure at renal artery stenoses

Atherosclerotic disease of the renal artery can lead to reduction in arterial caliber and ultimately to conditions including renovascular hypertension. Renal artery stenosis is conventionally assessed, using angiography, according to the severity of the stenosis. However, the severity of a stenosis is not a reliable indicator of functional significance, or associated differential pressure, of a stenosis. A methodology is proposed for estimation of the renal artery differential pressure (RADP) from MR imaging. Realistic computational fluid dynamics (CFD) models are constructed from MR angiography (MRA) and phase-contrast (PC) MR. The CFD model is constructed in a semiautomated manner from the MR images using the Isosurface Deformable Model (IDM) for surface reconstruction and a Marching Front algorithm for construction of the volumetric CFD mesh. Validation of RADP estimation was performed in a realistic physical flow-through model. Under steady flow, the CFD estimate of the differential pressure across a stenosis in the physical flow-through model differed by an average of 5.5 mmHg from transducer measurements of the pressure differential, for differential pressures less than 60 mmHg. These results demonstrate that accurate estimates of differential pressure at stenoses may be possible based only on structural and flow images.