For large AVMs that cannot meet the V12 dose constraint, how low are you willing to go in terms of single fraction dosing?   

We usually use a “volume staging” approach by treating part of the AVM to 18-20 Gy in one fraction (meeting the V12 dose constraint), and return to treat the remaining nidus about 2 years later. Generally  most or all of the treated nidus has occluded by then. There will of course b...