As I've said before, I believe in experiencing what I study. Gamma-ray bursts produce gamma rays, and therefore three and a half years ago my spine was irradiated with gamma rays at NIH. Magnetic fields help collimate astrophysical jets and produce the beams in pulsars, and therefore every two to three months I insert myself into the strong magnetic fields of MRI machines. Protons are a major component of cosmic rays, and therefore it is only fitting that yesterday I experienced proton beams.
The medical reason was to 'mop' up the region near my spinal cord where the tumor that was removed three months ago was located. The surgeon advocated irradiating this region because he could not remove the tumor cells intermingled with the nerve fibers which the tumor surrounded. However, the NIH radiation oncologist could not irradiate this region with gamma-rays (the standard treatment) without hitting the spinal cord with more radiation than it should receive; my spinal cord received the maximum radiation three and a half years ago. But protons can be focused into a narrow beam; more significantly, protons dump almost all their energy in a thin layer. The energy loss of a charged particle such as a proton increases as the particle's energy decreases. Thus the proton travels through material slowly losing energy until its energy falls below a critical value, and then the proton dumps its remaining energy in a very short distance. Protons of a given energy travel a specific distance and no further; the damage caused by the protons can be limited to the tumor.
Proton therapy was pioneered at the Harvard cyclotron that was housed in a building on Oxford St. near the physics building where I started my graduate work (I spent most of my time at the Observatory on Garden St.); as the cyclotron's use in physics research decreased (bigger accelerators were necessary) in the late '60s, its medical use-as a collaboration between Harvard and Massachusetts General Hospital (MGH)-increased. Finally, MGH built a dedicated facility (operational in 2002), and the Harvard cyclotron was finally closed down in 2003. Personal connection: a friend did his thesis work on the Harvard cyclotron, and his buddy-who also did his research on the cyclotron-was in charge of building the MGH facility. The other US facilities are at Loma Linda and Indiana, but a large number of other facilities will come on line soon.
Because the dose provided by protons can be tailored fairly precisely to a small region, the patient (i.e., me) has to be measured carefully for the treatment, and a medical physicist then must perform detailed calculations planning the treatment. Therefore I had to make a special trip up (Boston is north of Washington) to MGH a month before the treatment.
Of course, I wasn't just going to fly in and fly out the same day (especially for a 10am appointment); that would be too boring. I flew into Manchester, NH, (a hub for Southwest) the day before and visited the old textile mills in Lowell (now fascinating museums), dropped in on colleagues at Harvard, met a friend for dinner in Harvard Square and stayed with good friends. It took me a while to get used to the Boston drivers again.
At MGH I first met with Dr. Jay Loeffler, the head of the proton therapy department; I suspect he met with me as a courtesy to my doctor at NIH who trained at MGH. After we established that the MIT football team was a club while I was an undergraduate but became an NCAA team immediately afterwards, and I explained that astrophysics was good for the soul, he filled me in on my forthcoming treatment and proton therapy in general (I had of course already read the seminal paper by Robert Wilson from the late '40s). Dr. Loeffler lamented the demise of the old Harvard cyclotron and its building without even a plaque showing where thousands had been treated or a piece of the cyclotron being saved for display.
After meeting with Dr. Loeffler, I had two and a half hours to kill until the actual preparations. Visiting the Ether Dome was good for a quarter of an hour. The first operation with anaesthetic (ether) was performed at MGH in 1846 in the operation theater, now called the Ether Dome, at the top of MGH's original building (designed by Bullfinch). Then I wandered over to the proton therapy building (the doctors have their offices in the cancer building, the medical physicists in the building with the cyclotron) and dropped in on a medical physicist who is a friend of friends. He described the software used to plan the therapy, and gave me a cook's tour of the facility.
The preparations consisted of three procedures. First, a warm, flexible plastic mesh was draped over my face. When the mesh cooled, it hardened, forming the mask that would immobilize my head during the treatment. Second, two gold pellets were jabbed into the muscles of my neck as benchmarks for the X-rays used to align me for my treatment. Lidocaine was applied to the skin, so the insertion was not painful, but the pushing of the pellets into the muscle felt weird. The pellets will remain there forever. Third, a CT scan was performed of my upper body; this scan was the basis of all the planning.
The actual treatment was yesterday. This time Debbie accompanied me to provide moral support, and we went up a day early. Not to waste a trip to Boston, she had a meeting in connection with her next book project, we visited the address of my first home (a large three story house stands in place of my parent's small ranch-style house-part of my childhood has been razed!), dropped in on my aunt, and stayed with the same good friends. The day of the treatment started with a stop at the Fogg at Harvard where we visited some of our favorite paintings, and then lunch in the Square.
After another stop at the Ether Dome (this time for Debbie) and the obligatory hour wait in the waiting room (Sudoku puzzles are great for waiting rooms) we met with the doctor in charge of my treatment. After explaining what they planned to do-zapping the desired region with the beam from three directions-and after telling us that the treatment should cause no harm, he had me sign a waiver stating that I had been informed that the treatment could cause the loss of some of the nerves controlling my right hand and arm, and damage to my spinal cord...
Finally, I was treated. We were taken to a room where one side opens to a large cylinder on its side; the cylinder has a diameter of about 25 feet and its axis passes through the room about 3 feet off the floor. I lay on a narrow platform on this axis, and was then immobilized with the mask they made the previous visit and a strap across my chest. There were some human touches: I was asked for my choice of music (my response of 'classical' led me to hear the first movement of Vivaldi's "Four Seasons" over and over again), and they draped a pre-heated blanket over my chest. The platform was then moved a foot or two into the cylinder so that my torso jutted into the cylinder. Attached to the cylinder is a gantry from which the proton beam is injected into the patient, and the cylinder is rotated to aim the beam into the patient from the desired direction. Aligned with, and perpendicular to, the proton beam are two X-ray tubes that are used to ensure the correct alignment. The CT scans taken a month earlier were used to calculate what an X-ray image would look like for a desired beam alignment. After the cylinder was rotated into the right position, X-rays were taken, the actual images were compared to the expected images, and then the platform on which I lay was moved a millimeter this way and a millimeter that way until the measured and predicted images coincided. Only when the alignment was perfect was the beam turned on. Thus the beam was on for only a small fraction of the time I was in the treatment room.
As I mentioned, the proton beam goes a certain distance and then dumps most of the energy over a very short distance. They insert plastic of a calculated thickness into the beam to control the distance the beam travels in the patient, and they pass the beam through a rotating wheel with sectors of different thickness to increase the thickness of the layer in which the protons dump their energy. A brass mask shapes the beam perpendicularly. As a result, for each direction the patient is irradiated (three in my case) they have to construct a custom aperture for the beam. And while the beam is on there is a loud whir of the wheel inserted into the beam.
After the scannings, and the measurements, and the paperwork, and the traveling, and entering into a heavily instrumented room, and being immobilized, the treatment was...anticlimatic. One doesn't feel anything. There are no immediate side effects (and no long term side effects are anticipated). My eyes were closed because of the mask, and there were so many clicks and whirs, that I was not always sure when the beam was on.
Anyone who is unfortunate enough to have much contact with modern medicine eventually has a health insurance experience that should convince them that our system is for the birds (or better yet, our worst enemies). I just have. I discovered last week that through a series of misunderstandings about the necessary paperwork, my out-of-plan treatment at MGH did not have my HMO's pre-authorization, as is required. After much scrambling, uncertainty, the possibility that the treatment would be postponed, angst, Debbie sweet-talking the HMO into rushing the pre-authorization review (I couldn't get them to do so), a weekend not knowing whether the HMO would approve the procedure, more angst, etc., the pre-authorization came through while we were waiting to get onto the plane for Boston. Now, I did not feel my life was threatened and was merely extremely angry about a bureaucratic snafu when I had provided the correct information, but I can imagine what it would be like for a scared person whose life is much more dependent on a medical procedure and who does not have a savvy advocate such as Debbie.
The procedure is over, and in general I am feeling great. The unexplained low fever and tiredness that set in a few weeks after my operation has disappeared, leaving behind many blood tests, a detailed study of the health of my heart (to rule out an infection that affects the heart valves), etc. I should be back to the humdrum routine of MRIs every two to three months, followed by a comprehensive neurological exam ('can you feel this? Touch your nose with your eyes closed...'), followed by my updating Dr. Fine on the latest in astrophysics. Such boring routine I can live with for many, many years.