In the first picture, I have settled into my pod (the blue part under me). I'm wearing a hospital gown, open in the back. From my waist to my knees I also have a towel over me. This gives me the illusion of modesty, while the therapists tug and push my legs and hips into the position needed, as determined by laser beams. I get to keep my socks on; the tile floors are a bit cold. I'm holding a blue rubber ring, so my arms don't droop and possibly pull my body body out of alignment.
At the moment, the place from which the beam emerges is not in position; it's clearly aimed too high. I get positioned first, then the beam. Also, the collimators and plastic modulator are not yet installed in the nozzle.
The large darker disk behind me has two rectangular shapes. Each is the end of an x-ray arm. The whole disk rotates, to bring the x-ray arm into the proper orientation. The entire beam apparatus also rotates, including the gray-and-white "nozzle," the blue housing around it, and all of the beige steel behind that. The therapists have already put both the disk with the x-ray arms and the beam apparatus into approximately the correct orientation for treatment on my left side. When treatment is to be on my right side, the beam apparatus rotates to the top of the room and back down the other side, almost 180 degrees. The x-ray disk also rotates, about 90 degrees clockwise, so there is an x-ray arm at the top. Some people (prostate cancer patients and others) get treatment on both sides during the same session (one side at a time, of course), so they get to see all of the movement.
In the picture below, the initial alignment is complete. One of the x-ray arms has emerged from the back, and is positioned to look at the gold markers installed in my prostate. The beam apparatus rotates slightly, as necessary, and the bed may move slightly up or down, to get the prostate in the cross-hairs, so-to-speak. Note that the brass collimators and plastic modulator are sitting out in the foreground, ready to install in the beam apparatus after everything is aligned.
Next, the therapists retract the x-ray arm, install the collimators and modulator, and leave the room. The single cyclotron proton source is shared by the three treatment areas, so there may or may not be a wait of a few minutes. Soon I hear a whine that rises in pitch. This is the activation of the beam modulator that controls the intensity of the proton beam now being directed into the beam apparatus in my gantry. A couple of minutes later, the whine falls in pitch, and stops. The treatment is over, and I didn't feel a thing. The x-ray arm may come out again then, to check that everything is still in place; that got less common later in my treatment weeks, as I apparently have a prostate that doesn't move around much. When the therapists come back into the room they take the rubber ring out of my hands, lower the table, and help me down to the floor with the help of a step-stool. Nothing left to do but grab my ID card, ensure that the therapists have written down the time and gantry of the next day's treatment, and head for the conveniently located rest room. A quart of water is a lot to hold for an hour! Then I get dressed and walk back to the waiting room. At first I left the building quickly, but as I got to know the other prostate patients and their wives, I stayed and chatted a bit. When Ursula was waiting for me in the waiting room with the others, it was sometimes difficult to