Novel 4D-Flow MRI to Assess Quantitative Arterial Hemodynamic Response after Brain Stereotactic Radiosurgery (SRS) for Cerebral Arteriovenous Malformations (AVMs)

Abstract

For unresectable cerebral AVMs, ablative SRS is standard of care. However, obliteration may take years, during which period risk of hemorrhage is uncertain. 4D-Flow MRI, a velocity-encoded phase-contrast MRI technique used to assess cardiac hemodynamics, has potential as an early marker of treatment response to SRS. Here, we assess changes in blood flow in AVM feeding arteries after brain SRS using 4D-Flow. Patients: Retrospective review of AVM patients treated with SRS at a single institution. Four patients were identified who underwent 4D-Flow MRI prior to or within 1 month of treatment (baseline) and at least one subsequent time point (first-follow up). Imaging: Imaging was performed on a 3T scanner with dedicated head coil. 4D-Flow sequences were based on a 3D spoiled gradient echo sequence with resolution 1.12 x 0.98 x 1.6-1.8 mm. Three directional velocity encoding gradients were used with Venc 100-200 cm/s. In addition, T1 post-contrast, T2, and 3D-Time of flight (TOF) angiography images were obtained to identify the AVM nidus and feeding arteries. Analysis: In each case a feeding artery was selected that could be traced distally to the AVM on both baseline and follow up images. Measurements were made in two locations within each feeding artery. A distal measurement was made as close to the AVM nidus as possible. A proximal measurement was made in the most proximal segment of the feeding artery (e.g. M1 segment of MCA). A control measurement was made in the corresponding contralateral proximal artery. Blood flow was measured using imaging software with FDA clearance for clinical 4D flow post-processing for cardiac MRI. Changes in blood flow were assessed for significance using two-tailed paired t-tests. Baseline AVM nidus volume ranged from 4.6-10.2mL. All AVMs were treated with single fraction SRS, prescription dose 16-20 Gy. Follow up time ranged from 3-17 months. Baseline and follow up blood flow measurements in L/min are displayed in table 1. In feeding arteries, blood flow decreased by a mean of 49% proximally and by 54% distally (both p<0.05). There was no detectable change in blood flow in control arteries (mean change 12%, p = 0.28). Blood flow through cerebral AVM feeding arteries decreases significantly after SRS by time of first follow up as assessed by 4D-Flow MRI. 4D-Flow is a promising early marker of AVM response to SRS. Future studies are needed to determine if this hemodynamic response correlates to decreased risk of hemorrhage prior to radiographic AVM obliteration.Abstract 232; Table 1PatientSpetzler-Martin GradeDistal BaselineDistal Follow UpProximal BaselineProximal Follow UpControl BaselineControl Follow Up130.120.040.500.210.230.24240.290.130.560.280.030.05340.160.070.410.180.080.07420.420.240.510.350.250.26meann/a0.250.120.490.250.150.16SDn/a0.130.080.070.070.100.10 Open table in a new tab