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Shadowing Radiation Therapy
Reflection on my first week in a cool field.
Shadowing Radiation Therapy
This week I shadowed some radiation therapy treatments at the Mayo Clinic in order to see hands on what I’m helping build AI tools for. It was absolutely incredible seeing everything that I’ve learned about in research papers and textbooks play out in real life. More than that though, I just gained so much more appreciation for the power of human beings and what we have accomplished as a species.
The treatments I shadowed were all performed on linac machines. The name “linac” is short for “linear accelerator” which is a method of speeding up electrons close to the speed of light. Inside these machines, electrons are sped up to near light speed then shot into special metal plates in order to create x-rays. This beam of x-rays is then shaped by a collimator, which is a sort of mouth with independent teeth that open and close to get a desired shape, in order to aim at targets within patients with sub-millimeter accuracy.
The fact that linacs exist is a remarkable testament to human ingenuity. They were created by the coordinated efforts of physicists, biologists, oncologists, computer scientists, engineers, business leaders, et cetera, all with the mission of destroying cancer. It just boggles my mind how impressive these machines are.
Each treatment on a linac is a highly complex yet supremely organized process starting as soon as the oncologist orders the treatment for the patient. The first part of a linac treatment is called a “simulation” or “sim” for short. In a sim, the patient comes to the hospital and goes through a mock practice run of the real procedure. The patient is placed on the treatment bed, which is called a couch, and a mold of their body is made to hold them in place. They are then CT scanned to see where the tumor and all their other organs are, and then they are free to leave.
The CT scans from the sim are then given to medical physicists and dosimetrists who go through the scans and mark where the tumor is and where all the sensitive organs are. They then determine how much radiation to blast different parts with, and from which angles. The unfortunate part about radiation therapy is that x-ray beams go in a straight line all the way through the patient meaning that lots of healthy tissue gets hit by the beam during treatment. But by hitting a tumor at different angles we can blast the tumor multiple times while minimizing damage to healthy tissue. The goal of the medical physicists and dosimetrists is to find the best possible doses and angles to hit the tumor with.
The last step is the treatment, which is the part I shadowed. I sat behind the scenes in a control room that looked like a NASA space command, or military battle station. There were 15 computer screens all monitoring different aspects of the treatment. Each linac has it’s own control room with 3 designated people that run it.
The main difficulty of the treatment day is getting the patient into the same position as they were in during the sim. One of the biggest things I learned this week is that humans are really squishy. Sometimes tumors slightly shifted or grew or shank between the sim and treatment. Sometimes, little things like passing gas, breathing, or bladder fullness moves stuff around. But remarkably, these changes are usually small enough to not affect the treatment, where tolerances on most treatments were around a centimeter, and I guess big deviations are rare enough that I didn’t see any this week. For things like brain treatments the tolerances are much tighter, and for those there were additional procedures and checks that the doctors made to ensure that the patient was in the right position.
The bulk of the treatment time is spent putting the patient into the bed, then doing a few checks to make sure that the patient is in the right position. Once they confirm that they are good to go, the whole operation takes only a few minutes. It’s an enormous amount of prep work for such a fast procedure. There are no incisions or anything either, so after the treatment the patient can just get up and go about their day.
For many patients instead of receiving a large dose, they get several smaller doses spread out over multiple treatments on different days, so many become friendly with the therapists and treatment providers. One of the highlights of the week was hearing a happy patient say goodbye to a therapist as she left. She said something along the lines of “You were lovely, but I hope to never see you again.” Evidently her cancer went into remission.
The crazy thing about radiation therapy, besides the science and the operations, is that it is really effective. Success rates of radiation therapy for certain cancers can be above 95%. That is an enormous amount of people who are beating cancer. This is really the best part: knowing that we are making a real difference in a lot of people’s lives.
I learned a lot this week. This is such a cool field. It’s incredible reflecting how far we’ve come in the past 100 years and really exciting to think about how much will change in the next 100 years. I am very glad to be a part of this.
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