This is Ganesh, medical physicist at Univ of Arkansas for Medical Sciences and I attended Dr Agazaryan's talk on Brainlab at the AAPM annual convention. I have a follow up question on the topic. We have been using Brainlab MME ver 2.0 with Exactrac localization for little less than an year now. Our physicians define the tumor contours (GTV) for multiple mets on CT after fusing with MR. When it comes to defining the target (CTV or PTV) using a treatment margin, I would need an overall treatment error for a single-iso multi-mets plan and a single cranial tumor plan. We use single iso and multiple non-coplanar arcs in Truebeam sTx and planning is done on Brainlab MME ver 2.0. Our suggestion had been 0.5 mm margin for any target within 5 cm from txt Isocenter and 1 mm beyond that. I would like to double-check these margins with what is used at other institutions. It would be great if you can share your thoughts. We wont necessarily use it per se, but would like to have a good comparison point.