Radiosurgical treatment planning of AVM following embolization with Onyx: possible dosage error in treatment planning can be averted.
Treatment of arteriovenous malformations (AVM) of the brain is challenging due to the size and location of the nidus-proper and its proximity to the cerebrovascular circulation. Recent advances in catheter techniques and new embolization materials such as Onyx (a liquid agent that is less adhesive and slowly polymerizing) have increased the probability of achieving obliteration. When planning radiosurgical cases following such embolization, however, one must be cognizant of the distortions introduced by this novel substance on imaging studies. A sample of Onyx was irradiated to define the attenuation per mm thickness. The difference in attenuation compared to water was determined. Dose calculations were performed using 3 methods of inhomogeneity corrections. Homogeneous calculations were compared to "standard" heterogeneity corrections and to "modified" heterogeneity corrections by assigning individual electron densities to the normal brain and the Onyx. The difference between the attenuation of water in comparison to the Onyx was approximately 3% for beam energy of 6 MV. Best calculation results were achieved when using the modified inhomogeneity corrections which were based on the actual attenuation of the Onyx. The use of Onyx caused significant image artifact on MR and especially CT. As such, a correction must be manually introduced into the planning system to account for this potential error. Otherwise, dose calculation may be unreliable and could have dire consequences for patients receiving high doses of radiotherapy.
Shtraus
Natan
N
TASMC Stereotactic Radiosurgery Unit and the Institute of Radiotherapy, Tel Aviv Sourasky Medical Center University of Tel Aviv, 6 Weizman Street, 64239, Tel Aviv, Israel. natans@tasmc.health.gov.il
Schifter
Dan
D
Corn
Benjamin W
BW
Maimon
Shimon
S
Alani
Shlomi
S
Frolov
Vladimir
V
Matceyevsky
Diana
D
Kanner
Andrew A
AA
D001165:Arteriovenous Malformations / Q000628:therapy*; D003952:Diagnostic Imaging; D004121:Dimethyl Sulfoxide; D004621:Embolization, Therapeutic / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D018810:Magnetic Resonance Angiography / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D011145:Polyvinyls; D011300:Preoperative Care; D016634:Radiosurgery / Q000379:methods*; D011878:Radiotherapy; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome
C450660:Onyx copolymer; D011145:Polyvinyls; D004121:Dimethyl Sulfoxide
Neurosurgery. 2008 Jun;62(6):1213-25; discussion 1225-6
18824988
Neurosurgery. 2007 Aug;61(2):244-52; discussion 252-4
17762736
Expert Rev Med Devices. 2006 Nov;3(6):705-15
17280535
AJNR Am J Neuroradiol. 2007 Feb;28(2):371-7
17297015
Int J Radiat Oncol Biol Phys. 2008;71(1 Suppl):S126-30
18406910
Neuroradiology. 2008 May;50(5):439-42
18172630
Stroke. 2002 Dec;33(12):2794-800
12468772
J Neurol Neurosurg Psychiatry. 1986 Jan;49(1):1-10
3958721
J Neurosurg. 1990 Sep;73(3):387-91
2384776
Neurosurg Focus. 2009 May;26(5):E13
19408991
AJNR Am J Neuroradiol. 2006 Jan;27(1):162-76
16418378
Stroke. 2009 Jun;40(6):1973-9
19359648
J Neurol Neurosurg Psychiatry. 2002 Nov;73(5):547-51
12397149
Neurosurgery. 2008 Aug;63(2):239-43; discussion 243
18797353
Neurology. 1996 Apr;46(4):949-52
8780070
AJNR Am J Neuroradiol. 2007 Jan;28(1):172-7; discussion 178
17213451