Measurement of pressure drops at arterial stenoses from MR imaging

Atherosclerotic disease of the renal arteries can reduce blood flow to the kidneys leading to disorders including hypertension and renal insufficiency. Patients who benefit from invasive revascularization procedures have significant pressure drops at the renal artery stenoses. A computational methodology is presented for measuring pressure drops at renal artery stenoses from magnetic resonance (MR) imaging. The methodology is comprised of a computational fluid dynamics (CFD) model of blood flow with realistic vessel shape and flow rates. Realistic vessel shape is derived from contrast-enhanced magnetic resonance angiography (MRA) with a deformable model. Flow rates are measured from phase-contrast MR respectively. The methodology was applied to the case of a patient with 30% stenosis of a renal artery. The finite element solution was obtained with a volumetric mesh of 10⁶ elements. A physical flow-through model was constructed with similar shape, flow rates and fluid viscosity. The peak pressure drop measured by the CFD model was 60% greater than that measured from the physical flow-through model (33.8 mmHg and 21.1 mmHg respectively). The blood velocity vector field was obtained with particle image velocimetry (PIV) and will be used for improvement of the CFD model.