title: Time-of-flight magnetic resonance angiography imaging of a residual arteriovenous malformation nidus after Onyx embolization for stereotactic radiosurgery planning. Technical note.
abstract: This report demonstrates that time-of-flight (TOF) MR angiography is a useful adjunct for planning stereotactic radiosurgery (SRS) of large arteriovenous malformations (AVMs) after staged embolization with Onyx. Onyx (ethylene vinyl copolymer), a recently approved liquid embolic agent, has been increasingly used to exclude portions of large AVMs from the parent circulation prior to SRS. Limiting SRS to regions of persistent arteriovenous shunting and excluding regions eliminated by embolization may reduce unnecessary radiation doses to eloquent brain structures. However, SRS dosimetry planning presents unique challenges after Onyx embolization because it creates extensive artifacts on CT scans, and it cannot be delineated from untreated nidus on standard MR sequences. During the radiosurgery procedure, MR images were obtained using a GE Signa 1.5-T unit. Standard axial T2 fast spin echo high-resolution images (TR 3000 msec, TE 108 msec, slice thickness 2.5 mm) were generated for optimal visualization of brain tissue and AVM flow voids. The 3D TOF MR angiography images of the circle of Willis and vertebral arteries were subsequently obtained to visualize AVM regions embolized with Onyx (TR 37 msec, TE 6.9 msec, flip angle 20 degrees). Adjunct TOF MR angiography images demonstrated excellent contrast between nidus embolized with Onyx and regions of persistent arteriovenous shunting within a large AVM prior to SRS. Additional information derived from these sequences resulted in substantial adjustments to the treatment plan and an overall reduction in the treated tissue volume.
authors.affiliation: Mallinckrodt Institute of Radiology, Washington University School of Medicine, Saint Louis, Missouri 63110, USA.
authors.forename: David N
authors.initials: DN
authors.lastname: Loy
authors.forename: Keith M
authors.initials: KM
authors.lastname: Rich
authors.forename: Joseph
authors.initials: J
authors.lastname: Simpson
authors.forename: Ian
authors.initials: I
authors.lastname: Dorward
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Santanam
authors.forename: Colin P
authors.initials: CP
authors.lastname: Derdeyn
mesh_terms: D000328:Adult; D016477:Artifacts; D001488:Basilar Artery / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D001933:Brain Stem / Q000098:blood supply / Q000503:physiopathology; D004121:Dimethyl Sulfoxide / Q000009:adverse effects / Q000627:therapeutic use*; D004621:Embolization, Therapeutic / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D011145:Polyvinyls / Q000009:adverse effects / Q000627:therapeutic use*; D011237:Predictive Value of Tests; D011300:Preoperative Care / Q000379:methods; D016634:Radiosurgery / Q000379:methods*; D012086:Reoperation / Q000379:methods; D055502:Secondary Prevention; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: C450660:Onyx copolymer; D011145:Polyvinyls; D004121:Dimethyl Sulfoxide