Simulation is a process carried out by the radiation therapist under the
supervision of the radiation oncologist. It is a mock-up procedure of
a patient treatment. Inside the simulation room is a CT scanner specifically
designed for the radiation therapy department. Simulation is the beginning
step of starting your radiation therapy treatment.
How Is Simulation Performed?
The main goal of simulation is to assure that you will be in the same exact
position every day for your radiation therapy treatments. To help achieve
this, various immobilization devices can be used and/or made. These devices
differ depending on the area of the body in which you are being treated.
The first step in the CT simulation is to make sure you are straight; there
are lasers is the room that help the radiation therapist straighten you.
To assure that you are straight, the radiation therapist does a quick
image on the CT scanner called a scout that shows how straight you are.
The radiation therapist may come in to move you a bit if you are not completely
straight, but your main goal is just to hold still.
After you are in a reproducible position and straightened, a CT scan of
the area to be treated will be done. Once the scan is complete the radiation
oncologist will come into the CT room and look at the scan. At this point
the radiation oncologist will mark the exact area on the CT scan that
he or she wants to treat. Once this is done the lasers in the room will
move to that point, and the radiation therapist will make marks on your
skin with a Sharpie® marker. After all the marks are made you will
get a few permanent tiny tattoos. These tattoos are given to ensure that
there is a permanent record of your treatment, and to enable you to be
positioned in exactly the same way each day for treatment.
Different Types of Immobilization That May Be Used
Wingboard – A wingboard may be used to position both arms above your
head. This is commonly used with patients with lung and esophageal cancer.
Having your arms above your head allows for a better treatment plan to
be designed.
Vac Lok™ – A Vac Lok™ is like a bean bag and consists
of a cushion and vacuum compression pump. The patient is placed in the
treatment position on a partially inflated cushion. The Vac Lok bag is
molded around the area to be immobilized and then deflated so that it
becomes rigid. Vac Lok bags are typically used to keep extremities (legs
as well as arms) immobilized so that you are in the same position every day.
Aquaplast (thermoplastic) Mask – These masks become pliable when
placed in a warm oven. When pliable the mask can be molded around the
patient’s head and neck area. The masks are perforated and allow
for normal breathing. When your treatment requires a mask, the treatment
marks are made right on the mask so there is no need for marks to be made
on your face.
Breast Board – A breast board is used to position the arms and shoulders
away from the chest and at the same time elevate the patient on an adjustable-angle
board for positioning and daily reproducibility. A wingboard is typically
attached to the breast board. We have two types of breast boards in our
department: with one breast board, patients lie on their back face up;
with the other breast board, the patients lie on their stomach face down.
Your physician will work with you to determine what breast board is right for you.
Procedures That May Be Done as Part of Your Simulation
These procedures are typically done only during the time of simulation
and are not repeated during the course of your radiation therapy treatment.
Contrast Agents – When performing a CT scan, contrast media may be
used to help differentiate anatomic structures or highlight an abnormality.
Contrast can be administered via three methods: intravenously (IV), orally
or rectally. The most common methods of administering contrast during
CT simulation are orally and intravenously.
Rectal Catheterization – A rectal catheter is a hollow, flexible,
soft rubber tube which is inserted into the rectum. A special contrast
medium is injected into the rectum through this catheter. The contrast
medium outlines the rectum and makes it easier to visualize on the CT scan.
After Simulation Is Complete
Once your simulation is complete, the radiation therapist will either give
you an appointment card with your starting date of treatment or let you
know that we will be calling you within a week or two to schedule your
first appointment. Treatment planning varies depending on the type of
treatment you are having, so it may take anywhere from three days to a
couple of weeks to plan your treatment.
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