Austin Center RADIATION Oncology

CT Simulation

CT simulation

Once it is decided that radiation therapy is the best treatment option for you, you will be scheduled for a CT simulation planning “mapping” session here at the radiation center. The purpose of the CT simulation is to determine the exact location, shape and size of the tumor to be treated. This appointment will take approximately one hour.

The CT technician will come and get you from the waiting room and take you to the CT room. A signed consent will be obtained before you start the scan. You will be asked to remove your clothes from the waist down and will be given a sheet for cover. You will be positioned on the table in the same position that you will be in for each treatment.

Next, a small tube will be placed in your rectum. A tube will also be placed in your urethra and filled with water. A soft clamp will be placed on your penis to hold in the fluid.

Several stickers will be placed on your hips and lower abdomen and lined up with the laser light cross points on the machine. You will be asked not to move. You will be asked to breathe normally during the scan.

After the scan is complete, Dr. Garza will review the images and confirm the exact body placement for treatment. A body mold called a Vac-lok will be placed under the bottom half of the body. This mold will be wrapped and held around your legs and feet to create the exact mold. This individualized mold will be used for each treatment.

After Dr. Garza has approved the images, the stickers will be removed and dot-sized tattoos will be made in place of the stickers. The tattoo marks are used by radiation therapists to ensure proper alignment for each treatment. This will conclude the CT simulation session.

A schedule for treatment will be given to you at this time. Treatment will begin approximately two weeks after your CT simulation. If there are any special instructions before you begin treatment, the radiation therapists will contact you.


Patient instructions for CT Simulation

Goal: “Empty Rectum and Full Bladder”

Keep your rectum empty prior to the scan by using two enemas.

  1. Use the first enema (i.e. Fleets Brand enema) three hours before bed the night before your appointment.
  2. Use the second enema the day of your appointment, starting three hours before your appointment time.

Keep your bladder full prior to the scan by urinating and defecating one hour prior to your appointment followed by drinking 16 ounces of water,  one hour before your appointment time.  Do not urinate until after completion of simulation.

Simulation process

  • We will ask you to remove your clothes from waist down.
  • You will be placed on the treatment table in the same position for all of your treatments.
  • A small soft tube will be inserted in your rectum. This will be used as a marker for your rectum on the imaging.
  •  A small amount of fluid will be inserted in your urethra. A soft penile clamp will be placed on the penis to keep the fluid in place.
  • You will not need pain medications or sedatives for the imaging.
  • If you drove yourself to the appointment you will be able to drive yourself back.
  • You do not need to fast; you may have a normal breakfast and lunch.

Optional:  Three days before your simulation, start taking Simethicone (Gas X) 120-125 mg ORALLY four times daily after meals and at bedtime for maximum dose of 500 mg/day.  If you choose not to use the Simethicone and a rectal bubble is seen on the scan, we may have to use a small rectal tube to evacuate any air in the rectum.  You may stop the Simethicone after the simulation is complete.

We will confirm your treatment start date, after the simulation is complete. If you have questions about this procedure, contact the Austin Center for Radiation Oncology.