The Simulation
After your first consultation with a Radiation Oncologist, they will set up an appointment for you to come in for what's called a "Simulation."
What is a Simulation?
The simulation is basically a CT scan, or CAT scan. Even if you've had scans done in the past, you will have one performed in the radiation oncology department. This one is needed for the radiation oncologist, dosimetrist, and physicist to locate your tumor and its surrounding tissues. They will use this information to plan the radiation treatments specifically for your anatomy. Depending on your oncologist, you may or may not receive intravenous contrast for your scan. Contrast is sometimes needed in order for the provider to locate the exact position of your tumor.
Why is my Simulation Important?
You will meet a radiation therapist that has been specifically trained for your simulation. They will work with you to find a comfortable position for you to receive your treatments. This position will be used every day that you come in for radiation. It's important that you communicate with your simulation therapist, they can make adjustments to your position in order for it to be tolerable to you on a daily basis. Once they have positioned you and have performed the scan, it will not be possible to make adjustments. Please be sure that you will be able to hold this position for at least 20 minutes every day during your treatment. If something is uncomfortable, please speak up, your therapist will be able to try different things to help you.
How will I be Positioned?
Your simulation therapist will work with you and the oncologist to determine the proper position in which you will receive your treatments daily. They will try to move unaffected body parts out of the way of the radiation to ensure that no radiation dose is delivered to healthy areas of your body. If you feel the therapist moving different parts of your body around, it's so that they can achieve the most direct path to your cancer while keeping healthy tissue safely out of the way. Radiation treatments today are so precise that most of your normal body tissue can completely avoid any radiation dose.
Will I get Tattoos?
The short answer is: most likely yes. There are a few rare circumstances where a person would not receive tattoos for radiation, but the majority of people will. It'll depend on the area where you are receiving treatment, but most likely you will receive anywhere between 3-5 of them.
These tattoos are permanent. They are done with a sterile needle and sterile tattoo ink. Your radiation tattoos are black in color and very small, about the size of a small freckle. After you receive your tattoos you may shower as normal, they will not wash off. Many patients who receive tattoos will not be able to find them but don't worry, they're still there. Radiation Therapists are trained to spot the tattoos, we'll find them!
Depending on the location of the tattoo, some people may find them more or less painful. We'll say that it's kind of like a small bee sting. The spots where you were tattooed may become itchy later that day, you can use anti-itch creams if you like, and try not to scratch.
Simulation for Cancers of the Chest
If you are being treated for breast cancer, lung cancer, or any other location in your torso, they will attempt to place your arms up above your head. There are two reasons for this, first: to avoid radiation dose to your arms. Second: it's going to make it easier and more accurate to position the rest of your thorax when your arms are out of the way.
There are many accessories that are used for patient positioning in radiation oncology. The therapist might create for you what's known as a "vac bag" or "vac loc." This device is kind of like a large bean bag chair, it will mold itself to the shape of your body using an air pump. If there is a vac bag made for you, the therapists will keep it in the department and bring it out for each of your daily treatments.
For radiation treatments to the breast, lung, or thorax, you will receive two tattoos on opposite sides of your rib cage, the therapists will use these daily to ensure that your body is not rolled and that you are flat on your back. You will also receive anywhere from 1 to 3 tattoos down the center line of your chest, the therapists will use these tattoos to make sure that you are laying straight down the middle of the treatment table.
Simulation for Cancers of the Head and Neck
For head or neck treatments, your simulation therapist will make a thermoplastic mask customized to the shape of your face. This is a special plastic sheet that becomes soft when the therapist places it in an oven or a hot water bath. Once the material is soft, they will drape it over your face and/or neck. The mask will feel very warm but will not burn you. As the plastic cools, it will harden, and will keep its shape for the duration of your treatments.
There are some special considerations if you are having a mask made. They will have you remove any oral devices (like dentures) and anything else that is bulky (earrings, necklaces, glasses, and hearing aids). If you have a port on your chest for chemotherapy, don't worry, the therapists are used to this and have ways to accommodate. They may end up cutting out a section of the mask so that it will not cover your port as the pressure from the mask can be painful.
It is also important to keep your physical appearance consistent from the day the mask is made until the completion of treatment. If you have facial hair, that's OK, but keep it the same from day to day. Growing extra facial hair can make the mask tighter and will be uncomfortable, while shaving off facial hair that was present making the mask, will result in the mask being too loose, and can jeopardize the accuracy of the mask. For the same reasons, long hair should remain the same. I once had a patient who had to cut out her hair extensions because the mask would no longer fit (the mask was made before the hair extensions, and the added material under her head made it too snug to fit the mask onto her face).
Simulation for Prostate Cancer
If you are going to receive radiation to your prostate or pelvis, the simulation therapist will concentrate on ways to keep your legs still. You might have a mold made of your legs, and every day when you come in for treatment, your legs will fit right back into your mold. Some clinics however, use a generic knee pillow that has grooves in it where your legs will fit.
You will receive 3 tattoos. Two tattoos on opposite sides of your hips, the therapists will use these daily to ensure that your body is not rolled and that you are flat on your back. You will also get one tattoo somewhere below your belly button, the therapists will use this one tattoo to gauge your left to right position on the treatment table.
Treatment to the prostate or prostate fossa requires an extra few considerations on your part. The prostate is a gland that is not fixed in place, meaning it can be pushed around your abdomen based on the contents of your intestines and your bladder. During your first consult with the radiation oncologist, they will advise you that for every treatment (including the simulation) you will need to have a full bladder and an empty rectum.
What this means:
You should try to develop a pre-radiation routine. Get a water bottle with measuring marks on it and start with a comfortable amount of liquid about 30 minutes before your appointment. Drink the same amount at the same time every day before radiation. The therapists will give you feed back when they perform your pre-treatment scan. You can raise your water intake if they say that your bladder is not full enough, and vice versa if your bladder is too full, lower the amount that you'll drink the next time. The purpose of having a full bladder is that your bladder will act as a barrier. A full bladder can push your small intestine up and away from the radiation area. This will reduce the likelihood of any uncomfortable gastro-intestinal side effect.
Your rectum can also make trouble for the position of your prostate. If it is full and you are in need of a bowel movement, the material can push your prostate forward. The problem with this is that the rectal walls will receive more radiation dose than they are intended to, this might lead to some uncomfortable gastro-intestinal side effects down the road.