A Day in the Radiation Machine

December 13, 2008

I have completed four actual and one simulated radiation treatment. Here is their scenario.

It takes about an hour and five minutes to get from our house to the MOHPA clinic in Maplewood. We have been arriving about 15 minutes early. For a 4:00 pm treatment we would leave about 2:45. The drive is easy, a bit long, rolling Wisconsin countryside, including two herds of buffalo.

At the clinic I sign in, by typing my last name into their ‘radiation computer.’ When I click enter, the radiation therapists get a note on their computer that I am here. At the appointed time—so far they have been late only once, more on that below—one of them comes to call me in to the treatment room. In the room I take off my shoes and empty my pockets. One of the therapists holds a modesty towel close to my belt and I undo the belt and slip down the pants and underpants far enough so that I expose the three tattoos that they use to line me up. You can see one of the tattoos in the photo at the above left. It is about 2 mm wide.

As you can see on the picture above on the right, I lie on a bench, an elaborately technical bench about 19 inches wide and seven feet long. My feet go into the mold (the white thing under my feet) that they made on my first planning trip there in November. My head lies on the pillow and, to keep my arms from flopping around, I hold a plastic ring which lies on my chest; that’s what my hands are doing in the picture. The bench has no padding. The idea is that my body must be in the exact position that it was in on the planning day. Padding would add another element of inexactness so there is none.

After I lie down the therapists move me around using several laser beams targeted on my tattoos so that I am in the exact same position, or nearly so, as I was on the planning day. You can watch this process in the movie below at the end of this post.

As you can see in the photo, above me is a nice large photo of a seascape. After the therapists leave the room, they dim the lights and the bench slides me into the radiation position closer to the center of the machine. I am in that position in the photo above.

During this first week, I have had a two-part treatment. In the first part, the imager (the square thing hovering above me in the picture) takes “quick CTs” of my pelvic area. Back in the control room—I will write about that another day—the doctor and the therapists align that CT with the one taken on the planning day. They are looking for an exact alignment, as they deal with tolerances of less than a millimeter. One of the reference points that they use are the gold markers that were inserted in me some time ago.

Once I am aligned the actual radiation treatment begins. The radiation unit (the radiator?), aka the 'linear accelerator', which is the round unit with the blue ring to my left in the picture, rotates overhead around to a position underneath me on my right. Call that position 1. In that position it emits two bursts of radiation. Position 2 is slightly higher and so on around me. Position 4 is directly above my pubic bone and then there are three more. Position 7 is underneath me to my left. In each position there are two bursts of radiation, that radiation being X-rays. They used to use cobalt but don’t anymore. The bursts are aimed at locations that the doctor has identified as highly probable to have cancerous cells. The bursts are not emitted for a length of time, rather they are emitted for units of strength. The actual length of the burst is determined by how long it takes to get through various environmental factors, such as humidity, in order to impart the number of units to me.

That’s it. The whole thing takes about 25-30 minutes from the time I enter the room until I put my shoes back on to leave. At this point in the sequence of treatment there are no noticeable side effects. Having one of these treatments is like having an x-ray of a broken bone. Right now I feel fine. No tiredness, no nausea, no pain in my pelvic area. And to repeat something I said before, no radioactivity that I carry around beaming at others. This is not the same as chemotherapy. They are microwaving me, not creating Chicken Kiev.



Let me add just a few notes. While this sounds like precise science, and it is, I am the factor that changes and must be accounted for. The issue is the amount of water in my bladder and the amount of gas and/or ‘matter’ in my bowel. I am supposed to duplicate the bowel/bladder configuration of the planning day. Well, easier said than done. The basic plan is urinate and evacuate one hour before the treatment. Since we are on the road that is not possible unless we happen to hit the Minnesota Rest Stop west of Hudson. I go when we leave. Then 45 minutes before the treatment I am to drink 16 ounces of water, which I do faithfully. The water reacts differently. In the early morning treatments, I never feel full, not like I have to urinate Right Now. The doctor even chided me that I was not full enough. In the afternoon treatments I often have the sensation, as my dad used to say, that my back teeth are floating. Twice I have gotten to the clinic and realized that I could not hold the stream for 30-40 for minutes, and one time, because of a technical problem they were 20n minutes late. Both times I snuck into the bathroom and relieved my self of a little of the liquid in the bladder, no small feat for a guy who wore Depends not even a year ago. And even after doing it twice the day the machine had problems, they still told me that my bladder was extremely full.

The point of this concern is that they want the bladder out of the way so that the small bowel gets pushed out of the radiation field. I will eventually get a better explanation but, as I understand it, they want to avoid the bladder and the rectum with the radiation and just hit the infected area. That is the point of the gold markers and the alignment and even of them moving the bench slightly one way or another.

One last note. I am learning all this. I am sure of the physical descriptions and sequences that I explain here. I am guessing at the rationales. I have asked the staff. They are patient and clear with their answers, but I probably have mistakes here. Just so you know.