It has been a long time since I wrote about my ongoing fight against cancer. A lot has happened in several months—many changes, several surprises, lots of ups and downs—and I have a backlog of half-finished posts that I hope to publish eventually. For now though, I wanted to write about one recent development and some interesting medical technology that I encountered because of it.
Last June I that one of my pupils was much smaller than the other. That medical mystery prompted several scans and tests. Unfortunately one of the scans revealed a small tumor in the back right of my brain. It is still a mystery whether that actually caused the problems with my eye, but it is obviously a(nother) serious problem.
I was strangely unbothered by the news. I already had tumors in my lungs and leg; what was one more when I was already undergoing chemotherapy? The problem is that the brain is protected by the blood-brain barrier that also prevents many chemotherapy drugs from acting on tumors in the brain. Fortunately, radiation therapy provides an alternative treatment for brain tumors, since the brain can withstand a larger dose of radiation than other tissues. My oncologist quickly referred me to a radiation oncologist. Within just two days, I had an appointment scheduled for radiosurgery.
There are several forms of radiosurgery, but all essentially bombard a tumor with a lethal dose of high-energy radiation. It sounds violent, but the treatment is noninvasive, painless, and has few side effects. The radiation oncologist recommended a particular technique/machine/brand called that is similar to the more widely-known (or at least better-marketed) .
To hold the patient's head absolutely still and to calibrate the machine, it is necessary to brace the patient's head with a custom-molded plastic mask. The mask is made out of thermoform plastic mesh that is bolted directly to the table. Forming the mask was the most interesting part of a long day in the hospital.
The mask started at the back of the head. The technician laid a piece of the plastic mesh across a bracket, forming a headrest.
Next, two strips passed across the forehead and below the nose. Biting down on a small tab kept the upper jaw in place.
The strips formed the foundation for the mesh body of the mask.
The technicians heated all of the plastic pieces in a steaming vat of water. It started out transparent, malleable, and uncomfortably hot, but quickly cooled, solidified, and turned opaque.
With the mesh solidly in place, the technicians marked key points for calibration. During the treatment itself, they attached small infrared beacons (which looked like glossy silver marbles) to the calibration points, allowing the machine to precisely determine the location of the tumor.
The completed mask looked like a crocheted statue head and fit like a clamshell.
It took several hours for the radiation oncologist and technicians to plan the treatment itself. They combined two earlier scans with the new calibration points to calculate the precise path of the machine. When they finished, the treatment took just 20 minutes. I simply laid on the table, the technicians reattached the mask, and the machine made ominous buzzing noises. A followup appointment in a month should show whether the treatment was effective.
(Thanks, , for taking pictures.)