Pretty much all IMRT radiation these days is arc based. The very nature of how IMRT is delivered is the principle that lots of very tiny (pin point even) beams of radiation from an unlimited number of angles, intensity, and duration, provide the exposure. Hence the delivery head of the machine rotates in an arc around your head to do so.
The most important part of IMRT technology is having a great RO, dosimetrist and physicist to do the map of what is going to get radiated and how much to where. Considering the primary, the known pathways of metastasis to the neck, and all the vital structures you would like to avoid or touch as little as possible, they come up with a map of what your radiation exposure looks like, almost like a topographical hiking map of concentric forms, each band with a different intensity and duration and spread of radiation. So regardless of the type of IMRT machine, and the software that runs it, it is really up to the staff to get you the optimum map that will give you resolution of the cancer while avoiding vital structures if possible. To suggest that heliarc IMRT is somehow better, is negating the fact that someone has to program it properly, without which it is no different than any other machine or software.
RO's and the dosimetrists/physicists that they work with, have to know anatomy like a surgeon does these days to get the optimal results. But given how few institutions out there that have not converted to IMRT delivery systems in the last decade (hardly any, and certainly no bigger ones), this is a discussion that you don't have to have with them.
The old adage that you can give a monkey a typewriter but that does not mean he can write War and Peace, comes to mind. The variable in all this is not the piece of equipment or software (the real breakthrough) it is the knowledge and experience of the human team being applied to use that tool. Since this is in the big versus smaller institutions section, it can take years for this team to get really good at using the IMRT technology as it requires a great deal of sophistication in anatomy, and actually working with this breakthrough software that is so completely customizable. Bigger institutions may get up to speed on things faster given that just see huge volumes of patients compared to smaller institutions. I have been told by several RO's that there is a significant learning cure involved when all this technology came about.
http://www.ncbi.nlm.nih.gov/pubmed/20384272http://oralcancerfoundation.org/facts/radiation.htmhttp://oralcancerfoundation.org/facts/imrt_radiation.htm
