Hannibal and the atom smasher

I walked into the radiation therapy room yesterday wearing a t-shirt from last year’s Shamrock Run in Portland, which was all it took to connect with the friendly young therapist who was coordinating my first session at the cancer center. He’s also a runner, so most of our chatter was about races we’ve run and how we train—not about cancer or why he’ll be seeing a lot more of me over the next four weeks.

The candy-colored lines on the
mask mark the outline of the nine
radiation angles used during
a 20-minute session. By the way,
that's my head inside the mask.

The craziest thing about launching part two of my cancer treatment plan is that I feel almost normal. The drug infusion I had 11 days ago hasn’t fazed me. I’ve been slightly fatigued since my surgery Aug. 5, but felt well enough on Sunday to run in a local 10k. I am totally asymptomatic. Most people I talk to have a hard time believing I’m being treated for metastatic melanoma.

Going bald in a couple of weeks should help with that. That’s about when the cumulative impact of 20 radiation treatments should start to kick in. Fatigue will likely be the worst short-term side-effect.

While I sincerely wish it wasn’t necessary, being treated with radiation is nonetheless full of wonder. This application of high-energy physics to clinical care makes an MRI scanner look like child’s play by comparison. There is absolutely no sensation to having my gray matter bombarded by x-rays. The only uncomfortable part of the procedure is the thermoplastic mask used to immobilize my head, which goes beyond anything Hannibal Lecter had to wear in “Silence of the Lambs.”

The radiation beam comes out of the gantry
above my head and can be rotated around me.

The technology being used on me is called intensity-modulated radiotherapy (IMRT), which uses radiation beams of varying intensities from nine angles to precisely radiate various parts of my brain. The radiation intensity of each beam is controlled, and the beam shape changes dynamically throughout each exposure. The goal of IMRT is to “sculpt” the radiation beam to avoid or reduce exposure to certain parts of the brain (the left hippocampus, in my case) and limit the side-effects of treatment. It can also deliver a higher dose to other areas, which for me is the cavity where the tumor and blood clot were removed at surgery.

The linear accelerator that generates the x-ray beam is an impressive apparatus. It uses microwave technology to accelerate electrons through what’s called a “wave guide,” then allows these electrons to collide with a tungsten target. As a result of these collisions, high-energy x-rays are produced. These x-rays are shaped by a collimator as they exit the machine to create the customized beams referred to above. If this explanation whets your appetite, here’s a good YouTube video about IMRT.

There’s something surreal about having accelerated atomic particles slamming silently into a heavy-metal target a few feet above your head, generating invisible rays that are bent by powerful magnets into beams that pass invisibly through the skull into your brain, and which then damage the DNA of cancer cells so they die and are eliminated from the body. I consciously experience none of this activity while immobilized in my Hannibal mask. Like so many things in life, I take as an act of faith that this marvel of technology will ultimately do me good.