TY - JOUR
T1 - Time-of-flight magnetic resonance angiography imaging of a residual arteriovenous malformation nidus after Onyx embolization for stereotactic radiosurgery planning
AU - Loy, David N.
AU - Rich, Keith M.
AU - son, Joseph Simp
AU - Dorward, Ian
AU - Santanam, Lakshmi
AU - Derdeyn, Colin P.
PY - 2009
Y1 - 2009
N2 - 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°). 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.
AB - 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°). 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.
KW - Arteriovenous malformation
KW - Computed tomography
KW - Ethylene vinyl copolymer
KW - Onyx
KW - Stereotactic radiosurgery
KW - Time-of-flight magnetic resonance angiography
UR - http://www.scopus.com/inward/record.url?scp=67651176154&partnerID=8YFLogxK
U2 - 10.3171/2009.1.FOCUS08246
DO - 10.3171/2009.1.FOCUS08246
M3 - Article
C2 - 19408991
AN - SCOPUS:67651176154
SN - 1092-0684
VL - 26
SP - 1
EP - 4
JO - Neurosurgical focus
JF - Neurosurgical focus
IS - 5
ER -