The nozzle for the proton beam (shown on the left), can rotate fully around the patient with millimeter accuracy. The technicians can see and communicate with the patient via closed circuit TV.
We also got to see the machine shop, but I didn't get any pictures there. That's where they create the masks (to hold the patient's head steady) and, hmmmm.... templates? for the Proton treatment. It's a pretty time consuming project, which is why Chase won't be starting treatment for another week.
The doctor marks the necessary treatment area on each MRI picture, the computers do their magic, and a computer guided machine creates a couple forms. One is about an inch thick piece of brass cut through with an outline of the tumor (or in Chase's case, the outline of his spine and the outline of his brain). This keeps the radiation from spilling over onto healthy tissue. The second piece is a thick piece of acrylic, machined to the shape of the tumor. Dr. Woo explained that the proton beam travels a specific distance before expending its energy, but once it goes through the acrylic, it can't go as far. The more acrylic in the way, the shallower the proton beam goes. Confusing, yes, but the forms look cool, and Chase will get to bring his home when he's finished treatment (oh no, take another suitcase, Buddy!)
At any rate, below's a picture of a mask (used for someone lying face up), and some of the acrylic forms for a spine (top) and brain (which you really can't see, below). The thinner brass plates are underneath each matching acrylic forms. 
The above photo's clickable, if you think that will help! There's also a video on the MD Anderson Proton Therapy center page (look for streaming video toward the bottom of this page).
More later...
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