It's natural to have fear, as ChristineB mentioned, and there are meds to help with anxiety. They do a simulation before the actual radiation to make a mask, set the markers for the radiation field. Maybe they can do additional "dry runs" until you are comfortable. IMRT, and assume you are having that, is open, and not enclosed like the PET, CT or MRI. It's just restrictive with the mask, which they can cut the plastic for the eyes, mouth, but each place is different. The first day is usually the hardest, and most who used anxiety medicationed, soon cease, after being more comfortable.

Some use meditation, mental imaging to help, and most places play music, and even may be able to bring your own cd's to play to help keep your mind occupied.

The weight loss can be a concern since most lose weight during radiation treatment, and can effect your recovery, and others, so you may want to see a nutritionist, speech and swallow therapist, if not already done, and most CCC have them on staff.

Good luck with everything.