We performed in-vitro experiments with pre- and post-operative carotid stenosis phantoms to elucidate and compare the hemodynamic characteristics of carotid artery atherosclerosis with and without a patch repair using 4-D flow imaging with MRI. 4-D MRI results showed that a strong jet emitting at the stenotic area impinges on the outer carotid wall of the pre-operative phantom for both patients. Their WSS is high not only near the stenosis but also the entire carotid relatively to their counterpart of post-operative phantoms. OSI was high in the outer wall of both post-operative phantoms. A glance of flow visualization results as well as the CT images might mislead one as if both post-operative phantoms relieved hemodynamic flow resistance. However, detailed studies on the hemodynamic feature of the flows revealed that the post-operative phantom with a patch has a higher WSS in the inner wall of the fork despite its wider lumen than the one without a patch. This is evidenced with the existence of a high velocity region near the inner wall. This is attributed to the presence of a strong recirculation zone induced in the opposite (outer) wall of the fork. The recirculation is necessarily caused with a sudden expansion of the lumen due to the patch repair and this kind of low shear, highly oscillatory region is thought to stimulate the growth of the atherosclerosis. The comprehension of these hemodynamic studies will help the management of pre- and post-operative carotid stenosis patients.

Hemodynamic comparison of carotid endarterectomy patch versus no-patch repair phantoms using 4-D flow imaging with MRI