MRI and Blood Flow in Human Arteries: Are There Any Adverse Effects?

PURPOSE: To explore if there are any adverse effects on blood flow in human beings when they are exposed to high or ultra high intensity magnetic fields in MRI, by investigating both qualitatively and quantitatively the effects of such fields on the velocity of blood and medically significant hemodynamic wall parameters such as wall shear stress (WSS), oscillatory shear index (OSI) and relative residence time (RRT) in four human large arteries.

METHODS: Blood flow in an artery is approximated as a flow through a uniform circular tube with rigid porous walls and the well-known McDonalds model is employed by using pressure gradient waveforms reported in the medical literature.

RESULTS: No significant change in the above parameters is observed up to 3T in all these arteries except a discernible change in the velocity and RRT in the pulmonary artery. Very significant changes are noticed in the above parameters beyond 8T in the pulmonary artery. The common hypothesis that low WSS and high OSI co-locate is not acceptable.

CONCLUSIONS: Our results suggest that the clinical consequences are to be carefully considered before exposing human beings to ultra high field MRI. It may not be appropriate to conclude anything about the effect of magnetic field on blood flow in human beings based on experimental studies on animals, which is one of the reasons for the contradicting reports found in the literature. A slip condition at the wall which is appropriate to hemodynamics is yet to be developed.