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Novel Planning Technique for Treating Large Volume Arteriovenous Malformations Using SRS

P Desai

P Desai*, B Caroprese, H McKellar, East Texas Medical Center, Tyler, TX

SU-E-T-482 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: An Arteriovenous malformation (AVM) is an abnormal connection between an artery and a vein bypassing a capillary. AVMs if left untreated can bleed and cause other neurological complications including death. Stereotactic radiosurgery is used as an alternative to conventional surgery to obliterate the AVM nidus (the central core of the AVM). SRS is generally restricted to small volume (less than 5cc) AVMs. Typically single fraction SRS doses of 1600-2000cGy are delivered to the contoured volume of the AVM while ensuring sharp gradients at the interface of AVM and normal brain. We discuss a novel strategy of dosing large volume AVMs (5-20cc) using a differential dose scheme that delivers 1600cGy at the rim and 2000cGy at the nidus of the AVM.

Methods:Accuray CyberKnife (G-3), Multiplan V3.5 treatment planning system. Patient CT, MRI and other imaging studies are sent to the Multiplan planning system. The neurosurgeons and the radiation oncologist at our site contour the AVM and the relevant anatomy. The contoured AVM volume is contracted by 2.5mm, and a rim is created by subtracting the previously contracted structure from the AVM. A treatment plan is generated using iterative planning ,using custom planning structures. The treatment plan delivers 2000cGy to the core of the AVM, and 1600cGy at the rim, while keeping the dose gradient at the AVM normal brain interface high, enabling us to spare surrounding brain tissue.

Results:Post treatment follow-up imaging done at 3, 6 and 12 months shows a gradual diminishing and obliteration of the nidus.

Conclusion:We conclude that this scheme of differential dosing enables us to treat larger volume AVMs effectively and safely.

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