Radiation and Cancer Physics

SS 32 - Physics 10 - Imaging for Response Assessment II

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

Wednesday, October 24
7:55 AM - 8:05 AM
Location: Room 217 A/B

Novel 4D-Flow MRI to Assess Quantitative Arterial Hemodynamic Response After Brain Stereotactic Radiosurgery (SRS) for Cerebral Arteriovenous Malformations (AVMs)
A. B. Simon, C. Li, R. Karunamuni, T. Retson, J. Handwerker, N. Farid, A. Hsiao, and J. A. Hattangadi-Gluth; University of California, San Diego, La Jolla, CA

Purpose/Objective(s): 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.

Materials/Methods: 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.

Results: 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).

Conclusion: 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. Table 1
Patient Spetzler-Martin Grade Distal Baseline Distal Follow Up Proximal Baseline Proximal Follow Up Control Baseline Control Follow Up
1 3 0.12 0.04 0.50 0.21 0.23 0.24
2 4 0.29 0.13 0.56 0.28 0.03 0.05
3 4 0.16 0.07 0.41 0.18 0.08 0.07
4 2 0.42 0.24 0.51 0.35 0.25 0.26
mean n/a 0.25 0.12 0.49 0.25 0.15 0.16
std n/a 0.13 0.08 0.07 0.07 0.10 0.10

Author Disclosure: A.B. Simon: Employee; Scripps Healthcare System. Stock; Medtronic Inc. C. Li: None. R. Karunamuni: None. T. Retson: None. N. Farid: None. A. Hsiao: Research Grant; GE Healthcare. Consultant; Bayer AG. Founder, Consultant; Arterys, Inc. J.A. Hattangadi-Gluth: Research Grant; Varian Medical Systems.

Aaron Simon, MD, PhD

Disclosure:
Employment
Scripps Healthcare System: Hospitalist: Employee; University of California San Diego: Resident Physician: Employee

Ownership
Medtronic Inc: Stock

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



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