Welcome Michael,

From what I know from previous neck dissections, the time between surgery and radiation is optimal between 4-6 weeks, but could be longer. Another thing is they try to keep the entire treatment package from surgery to radiation completion less than 100 days, more recent I heard around 89. If there is a delay they have time to work with, and could even increase the radiation if there are further delays.

The radiation types you mention are probably capable by one machine, namely by Varian, but all are external beam radiation.

IGRT uses a CT scan during treatment to monitor the tumor, such as shrinkage, and makes changes to its delivery.

SRT is more precise. There are other types brands that have names like Cyberknife, which is used often with brain cancer.

VMAT is an advanced form of IMRT where radiation is sculptured and delivered 360 degrees around patient. Another brand that is similar is Tomotherapy.

IMRT, Intensity Modulated Radiation Therapy, is what most if us get, and what you may too.

You mention one lymph node, but N2b is multiple ipsilateral lymph nodes, none greater than 6cm, so it's more than one node. Usually the effected nodes will get the same dosage as the primary, unaffected areas, around 54Gy or so.

I'm not sure if I read if you're having a neck dissection with the surgery? Sorry, just read yes. If there are negative prognostic factors from the surgical pathology, they may add chemo.

Good luck with the PET scan, and they will probably let you know of the dietary, exercise, medications, chewing gum restrictions for the test as they can effect it.