Radiation explained by a physicist and interpreted by me

Did you know I had a physicist? Neither did I. Turns out he’s a really nice guy and (shocker) super smart. I sat down with my physicist on Friday and got the low down on radiation which I am going to share with you now. It was amazing and I think everyone undergoing radiation should have such an opportunity to learn what is really happening to our bodies. I would like to add a disclaimer that even though I took a ton of notes, I’m quite sure that I will likely get something wrong in here (although I will do my best not to.) If any mistakes are made, I’m sure it is my misinterpretation, so please excuse my chemo brain.

First, meet my physicist. His name is Aaron. If you’ve had treatment at Exampla Lutheran Healthcare, I’d bet he was your physicist too.
Aaron

Aaron works closely with my Radiation Oncologist, the Dosimetrist and the techs who administer the radiation. My doctor picks the dose and location for treatment, then hands off that prescription to the Physicist. He does all the advanced calculations, calibrations and signs off on the plans. The Dosimetrist determines how to get the radiation that the doctor ordered as well as verifying the correct location and dose. My Dosimetrist is Mike and he is the one who got to come in and see me on the table when they were trying to figure out how to get my right foob out of the way (which apparently a lot of women freak out about).

First, the machine used to give radiation is definitely called the Linear Accelerator. They didn’t just pay to have that randomly put on the name plate on the wall. Who knew. The specific one used to treat me is a Varian Clinac. The machine costs about $3 million. It weighs approximately 7 tons and can rotate to 1mm precision. Considering all the weight being moved around there, that’s pretty freaking impressive. The machine uses 7 megawatts of power. Electrons are accelerated down the top of the machine to 99.9% of the speed of light, then pulled in a loop roller coaster style via a magnet until they are coming straight down and crash into a tungsten target where they are turned into radiation. They go through several filters and into yours truly. I’m honestly pretty amazed that they let me lay on the thing after learning all of this.

In order to understand radiation, you have to have at least a layman’s grasp of how the electromagnetic spectrum works. And that’s exactly what Aaron gave me. Here’s a visual:
EM_spectrum.svg

As you can see from the photo, everything travels in waves – from the low frequency radio waves to the high frequency gamma rays. There’s a lot more to this, but basically, everything to the right of the color spectrum are waves that are low enough that they don’t do damage to the human body. Radio waves, micro waves, infrared are all considered harmless (so please stop sending me links to cell phones causing cancer as they are in the microwave category). Everything to the left of the color spectrum does do damage to the human body. UV rays cause sunburn, X-rays expose our bodies to radiation but the waves are not strong enough to penetrate our bodies very much – we can see images on the x-rays, but most of the radiation stays at the skin level. Gamma rays on the other hand, go right through us. Guess which one they use for radiation?

So, here’s where everything comes together. The linear accelerator was created for testing. Scientists wanted to experiment to see what would happen when particles were accelerated and smashed into either each other or stationary targets with enough force to cause them to disintegrate and break down into the particles that make them up. Apparently this was really cool to the scientists as they made the SLAC (Stanford Linear Accelerator) which is 2 miles long. I’m glad I’m not laying in front of that one every day. Anyway, they created what is caused Ionization. This means there is enough energy to knock the electrons apart and the atoms can split. So with cancer, they are causing something called apoptosis which is really just a fun word to say. It means that the actual DNA inside of a cell gets destroyed. When the cell goes to split, it looks for that DNA to tell it how to create a new cell and when it realizes that DNA is gone, it dies because it doesn’t know how to do anything without that DNA map. Cancer cells, as I’m sure you know by now, are like crazy little freak cells that reproduce like wildfire and never get the message to slow down, so by killing their DNA road map, it forces them to die. So the trick is to do this to all the cancer cells while allowing enough time off for the normal cells to repair themselves. This is why we go in for small treatments every day over a period of time.

Before Linear Accelerators and the radiation that we get today, doctors knew that radiation killed cancer so they would hold radioactive rocks against a cancer patient’s body until the patient was good and burned. They had charts which were made up of photographs of patient burns and would hold them up to the current patient’s skin to determine if they were red enough to stop treatment. Love that science!

So, since radiation does not impact the body until the cells try to split and reproduce, there is kind of a delayed affect. This is why my burns stay active for a full week after treatment. This is also why there are persistent rumors that cockroaches would survive a nuclear holocaust. Cockroaches actually respond to radiation exactly like we do (more or less), but their cells reproduce at a much slower speed so the reaction is delayed. This lead us to an interesting discussion about how much radiation I could actually take before it would kill me. Since I am getting radiation to only part of my body, that factors into everything as well. The dosage I get every day to my chest is exactly the same dosage that patients getting ready for a bone marrow transplant get to their entire body. Since they are having such a large area treated, they have a much more severe reaction and are hospitalized for treatments. It obviously doesn’t kill them, but it seriously impacts their entire body. Fun fact – if I was given the total amount of radiation I receive in one week to my entire body in one treatment, it would cause my gastrointestinal system to liquefy and I would be dead in about a week. If more radiation was given, death would come from the central nervous system shutting down but again, I would be able to walk off the table and the effects would kick in later. Also interesting but horrible – people who receive spinal radiation may become paralized from their treatments. But it wouldn’t happen in the 5.5 weeks of treatment because the spinal cells regenerate so slowly. It would happen about 3 years after treatment was finished. Most of the knowledge from these dark areas come from accidents such as Chernobyl and seeing how people have been affected by large doses of radiation.

Anyway, back to happier thoughts – the unit of measurement for radiation is a gray. Using calculations, they determine my exact dosage on literally every spot on my skin. I was amazed at the computer images they showed me. Here is one showing four different views, and each view changed in real time depending on where they clicked on the screen.
4_image

So what you see here starting from the top left and going clockwise is a slice right through the middle of my body. You can clearly see the outline of my tissue expanders (and that the poor right one is not full at all) and everything is focused on my left chest area. The boxes show the different angles that the radiation is focused on me and the outline colors show different amounts of radiation which is hard to see. Since my chest is different thicknesses, this causes uneven treatment as the thicker part of my chest will need more radiation than the top of my fake boob where the flesh is thinner. This is where the leaves come in (those little metal things that move during my treatment). The next picture (top right) shows a 3-D image of my body with the path of radiation highlighted again. There are boxes for each angle of treatment. The bottom two images are side views (again cut in the middle) where dosage is again measured. They can literally click on any spot on that screen and find out exactly what dose I got. These estimates are tested every week using sensors that are taped to me during treatment.

The leaves are actually made out of tungsten and the paths they take are mapped out looking like this:
leaves_1

All those little blue lines are where they slide in and out and they have different screens showing each position they move to. The other one is used for my collarbone area and looks like this:
leaves_2

You may recall the photos I’ve posted in the past showing the lighted area of treatment on my collarbone along with the leaves. This is the inside view of the same – and it shows that the leaves are placed where they are to block both my spine and shoulder socket from receiving radiation. Pretty cool.

So, this gives you a basic understanding of how radiation actually works I hope. I find it fascinating. It’s also interesting to note that even though a ton of breast cancer patients receive radiation, radiating after a mastectomy is actually a pretty tricky process. The entire function of radiation is to penetrate the skin. The higher the frequency of the waves, the more it penetrates without damaging skin. This is called the skin sparing affect. So people who get radiation for internal cancers such as prostate or colon will frequently experience no burns at all. They can also get treatments from multiple angles rather than just one or two. The exception to this are head and neck cancers which can be treated from multiple angles, but often get severe burns. When someone has a mastectomy, the tissue is completely removed so the area that requires treatment is very close to the surface. It literally becomes skin on top of muscle with all the tissue in between removed. But in that space is where the cancer cells can live. So, treatment that is designed for deep penetration has to be “tricked” into treating basically the surface. This is why the doctor used wet towels over the surface of my skin. The wetness doesn’t necessarily attract the gamma waves, rather it fools the machine into thinking I have more flesh there and that it is actually penetrating and treating internally rather than on the surface. That is also why it is a “goal” to have my skin burn. That is the only way to verify that treatment has been given in the right area and close enough to the surface to kill the DNA in those sneaky cancer cells.

I also found out the answers to a couple of my questions – I have been wondering why, since the radiation is so precise, are the walls, floors and ceiling of the treatment rooms super thick concrete. If I don’t even have to change out of my clothes or take off any metal, what’s the deal with that? Turns out that the radiation does treat me, but it also scatters when it hits the surface of my skin as well as passing straight through my body. So, yeah, I guess they need some thick walls. Also, people often ask them for lead aprons that we’re all used to having draped on us for x-rays. Turns out lead would actually intensify the effect of radiation and are a huge no-no. So I’m glad I’ve never gotten one of those.

Tomorrow is my last treatment. It feels very surreal. But I’m very happy to be done. Now if someone would just hire Eric I could really celebrate. Here’s hoping!

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4 Responses to Radiation explained by a physicist and interpreted by me

  1. ericfickes@gmail.com says:

    Awesome post Jenn.

    *Eric Fickes *

  2. max says:

    Im impressed, I must say. Really rarely do I encounter a blog thats both educative and entertaining, and let me tell you, you have hit the nail on the head. Your idea is outstanding; the issue is something that not enough people are speaking intelligently about. I am very happy that I stumbled across this in my search for something relating to this.

  3. Serene says:

    Thank for sharing! Appreciate loads! Get well soon! 😉

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