Compensation for Signal Voids Caused by Turbulent Flow in Stenotic Vessels at 7T MRI: A Preliminary Study

Abstract

An abnormal vascular structure such as a stenosis induces a turbulent flow that causes signal voids in MRA images. This study aimed to propose a new method to prevent signal voids in stenotic blood vessels in conventional 3D time-of-flight (TOF) MRA images. 2D local excitation radio frequency (2DRF) pulse sequence was used in 7T MRI, and the feasibility of using this technique for imaging abnormal and turbulent flow was evaluated. The images obtained using the sequence were compared with conventional TOF MRA image of patients with MCA stenosis. Compared to conventional TOF MRA images, the images obtained using 7T MRI with a 2DRF pulse sequence showed high signal intensity in vascular segments that were expected to be abnormal, such as the origins of perforating vessels such as lenticulostriate arteries which are branches of the proximal part of the middle cerebral artery. 2DRF pulse also obviously compensated for the signal void within the stenotic vessels in the patient. The conventional MRA technique is sensitive to a turbulent flow, which causes a loss of signal and overestimation of the stenosis. The method proposed in this study could provide clear images of vascular segments that are difficult to evaluate owing to a severe stenosis.