Do I need to do anything to prepare for the simulation?
There are different things that need to be done prior to simulation depending on the reason and type of radiation you will be receiving (external beam radiation vs brachytherapy). Your doctor will review specific instructions with you at the time of your consultation but below are some general instructions for common radiation indications:
External beam radiation after surgery for endometrial or cervical cancer
About an hour prior to your simulation we will have you come to the clinic and the physician will place 3 small gold marker seeds near the top of the vagina (vaginal apex). The purpose of doing this is so that the physician can easily identify the vaginal apex on your CT scan. This is important because it helps us determine “how high” and “how low” to treat you.
This marker seed placement is done in one of the clinic rooms, takes about 5 minutes, and is very easy. No sedation or pain medications are needed. You will be put into the same position as you would be for a regular pelvic examination. The doctor will gently place a speculum inside the vagina and will then place the marker seeds. You may feel a brief pinch when the seed is placed. Significant bleeding is not expected or anticipated during this.
The marker seeds are left in permanently. It is safe for these to remain in the body and it is not expected that you will experience any reactions in the short or long term because of these marker seeds. These seeds will not cause you to set off alarms when going through the airport.
After the marker seeds have been placed we ask that you drink 30 ounces of water starting about 30 minutes prior to your simulation. In addition, it is best if you try to evacuate your bowels prior to coming to the clinic.
What happens during simulation?
The purpose of the simulation is to perform a CT scan of the area that we are going to treat in a position that we can reproduce for daily. The most typical treatment position is having the patient laying down flat on their back with their arms up on their chest. The CT scan from this simulation is sent to our dosimetrists and physicists and is used to plan how your radiation will be delivered based on your specific anatomy. The position that you are simulated in is very important because all of the radiation treatment planning is based on this position. Since the room that you are simulated in is different from the room where your radiation treatments occur we need to make sure that we can set you up the same way in both rooms. So in essence we are “simulating” what’s going to happen for your actual radiation treatments.
The type of simulation that is performed will depend on whether you are going to receive 3D-conformal radiation to the pelvis or intensity modulated radiation therapy with daily image guidance (IMRT/IGRT).
3D conformal radiation to the pelvis
For this type of simulation the patient is asked to come in with a comfortably full bladder. She will lie down on the CT scanner with her arms, most typically, on her chest. A special cradle will be molded around the legs below the knees to keep them in place. Once the patient is in position a CT scan will be performed of the pelvic region. No oral or IV contrast is used for this simulation and you do not need to fast prior to this simulation. At the end of the simulation a few small tattoos will be placed to help with alignment when you return to start your actual treatments. The entire simulation takes about 1 hour.
The simulation process when a patient is going to receive IMRT/IGRT takes an extra step (a bladder empty scan is done in addition to a bladder full one). The reason for this can be seen and explained through the following cartoons:
In these cartoons the yellow circle represents the bladder, the red oval represents the vagina, the brown circle represents the rectum, and the blue outline represents the area that will be treated with radiation. The first figure represents a typical example of the radiation field for 3D-conformal radiation. A large enough radiation field is used so we can ensure that all the targets are included with a generous margin. In treating with a larger margin organ motion (ie bladder/rectum being full vs empty) aren’t as relevant because the target will always fall within the radiation field.
When using IMRT we are able to sculpt the radiation dose to the areas at risk for cancer while limiting the dose to normal tissues that don’t need to be treated.
So in this cartoon one can see that the target for radiation is really the upper vagina (red oval) and tissues around it and the radiation field in blue is just covering this area with a small margin extending into the bladder and rectum.
Because we are using smaller margins it is imperative that we understand how organ motion (ie rectal/bladder filling) moves the target so that we can ensure we are properly treating the intended target. To accomplish this we do the simulation with an empty rectum (ie making sure the patient has a bowel movement prior to simulation and is not constipated) and do a simulation with the bladder full and another one with the bladder empty. What this allows us to do is to see how the target moves based on your bladder filling. The target is contoured on both the bladder empty and the bladder full scans and is then fused together. This fused target volume gives us confidence that the target will fall within this volume on a daily basis.
In order to be 100% sure that the target is being appropriately treated on a daily basis an image is obtained prior to your treatment daily and is reviewed to ensure that the target is indeed within the treatment volume. This is what is referred to as the image guidance portion of the treatment.
Here is an axial CT scan slice of an actual patient with her bladder full on the left and her bladder empty on the right. You can see that with the bladder (yellow) empty that additional bowel falls within the pelvis and that the marker seeds (red) are in a different place (also in part due to increased air in the rectum (brown). This example demonstrates the importance of daily image guidance and making sure that your bladder is consistently full during the course of your treatment.
We will start working on your plan and patients typically start treatment within 1 week from the time of their simulation. Prior to starting your treatment a port film is done. Sometimes this is done on the same day that you will be starting treatment and other times it’s done the day before. The purpose of the port film is to make sure that we are setting you up in the treatment room in the same position that you were in for the simulation.
Prior to each treatment you should have a comfortably full bladder and to the best of your ability try to stay regular with your bowel movements so that you don’t get constipated or have too much gas.
When you come in for your simulation before you leave you will be given a schedule with your treatment start date and time. For external beam radiation we start treatments at 7 AM and complete treatment at 6 PM.
For the actual external beam radiation treatments you will be brought to the treatment room that has a linear accelerator. This is the machine that actual generates and delivers the radiation. You will be put onto the radiation treatment table in the exact same position that you were in for your simulation. Radiation therapists are involved in helping to get you set up on the table. After you are set up the therapist will step out of the room. There is a camera and microphone in the room should you need to communicate with the therapist. In all cases weekly imaging will be performed to make sure that you are setting up properly and these films are reviewed by your physician. In some cases daily imaging may be performed prior to your treatment. These films give us information about your set up but don’t really give us information about whether you are or are not responding to treatment.
After your position has been verified the treatment will begin. You will see and hear the linear accelerator moving around you. You will be laying still. You will not see anything coming out of the machine or feel anything while you are being treated. The treatment takes about 5-10 minutes to complete. After the treatment is done you will be helped off of the table and you will be ready to leave the clinic. For your daily treatments you will not typically see your physician as the treatment set-up and delivery of the radiation is done by the therapists who are specially trained to do this.
For external beam you will see your doctor at least one time per week to discuss how you are doing on treatment. If you need to see him/her more often than you can let one of the therapists or nurses know and they can help coordinate this.
The most common chemotherapy agent given at the same time with radiation for gynecologic malignancies is cisplatin. This medication is given intravenously once per week by a medical oncologist. On the day that you get chemotherapy you should get your chemotherapy first and then come in for your radiation treatment afterwards.
Planning Session (simulation)
Vaginal cuff cylinder brachytherapy after surgery for endometrial or cervical cancer
About an hour prior to your simulation we will have you come to the clinic and the physician will place 3 small gold marker seeds near the vaginal apex. The purpose of doing this is so that the physician can easily identify the top of the vaginal apex on your CT scan. This is important because it helps us determine “how high” and “how low” to treat you.
**If you will be getting external beam prior to brachytherapy then you will already have marker seeds in place and you will not have to have this done again.
After the marker seeds are placed a foley catheter will be inserted into the bladder. This is done so that the bladder is drained for the simulation as well as so that we can place contrast into the bladder at the time of the simulation. This helps us better visualize it on the CT scan. Because a foley catheter is used we will write a prescription for an antibiotic (most commonly Cipro) to take once in the morning and once in the afternoon on the day of the simulation. In addition, it is best if you try to evacuate your bowels prior to coming to clinic.
Simulation for intracavitary cases
During this planning session you will be asked to lie on your back on a CT scanner. Your legs will be placed in stirrups and you will be positioned in the same way as you would be for a pelvic examination. The physician will then do a pelvic examination and evaluate which applicator will work best for your anatomy. The doctor will then gently insert the applicator into the vagina. After the applicator is properly inserted it will be stabilized. Your legs will then be brought down in the stirrups, contrast will be placed in the bladder via a foley catheter, and then a CT scan will be performed of the pelvis. The position of the applicator on the CT images will then be reviewed by your physician. If everything is positioned properly then the applicator will be removed, your legs will be brought down from the stirrups, and the simulation will be completed. If the applicator is not in the ideal location then it will be adjusted and another CT scan of the pelvis will be performed to verify its position. This entire simulation process takes about 1 hour. No intravenous contrast is used during this simulation.
Simulation for interstitial cases
This planning session is similar to the intracavitary one except for the fact that the small hollow tubes that are used for interstitial cases are placed in the operating room and then you are brought down to the Radiation Oncology Department for your CT simulation as opposed to having the applicator placed in the CT simulation room as is done with intracavitary cases.
Once you are brought to the CT simulation room you will be transferred from a gurney to the CT table. You will be lying down flat on your back for the simulation. Contrast will be placed in the bladder and the rectum. A CT scan will then performed of the pelvis. The images will be reviewed by your physician and he/she will decide whether any adjustments to the hollow tubes are needed. If adjustments are necessary then they will be made and another CT scan will be performed to assess the final location of the hollow tubes. This process takes about 1 hour. No intravenous contrast is used during this simulation. After the simulation you will be taken off of the CT table and a therapist will do some measurements of each of the hollow tubes that have been placed. These measurements are used to help us with treatment planning
Treatment can start the following day after the simulation. Treatment is typically given either two times per week (with at least 48 hours in between treatments) or every other day. Usually 3-6 treatments are given depending on the clinical scenario.
Treatment will start either later the same day as the simulation or the following morning. Treatments are standardly given two times per day (once in the morning and once in the afternoon).
You will be asked to empty your bladder prior to the insertion of the applicator and to the best of your ability try to stay regular with your bowel movements so that you don’t get constipated or have too much gas.
You will be an in-patient for this treatment so there is nothing extra that you need to do prior to your treatments.
When you come in for your simulation before you leave you will be given a schedule with your treatment start date and time. For brachytherapy we start treatment at 8 AM and complete treatment at around 6 PM.
You will be set-up in the same position as at the time of simulation. For the actual treatment you will not have marker seeds placed again and you will not have a foley catheter in the bladder. The applicator will be placed gently and secured into place. A CT scan will be performed to verify the position of the applicator. If minor adjustments need to be made they will and a CT will be done again. Once the applicator is in the proper position you will be transferred while in stirrups and with the applicator in place onto a gurney. You will then be transported next door to the brachytherapy suite and the applicator will be connected to the HDR remote afterloader. The doors will be closed (there is a camera and microphone in the room so you can communicate with us) and then treatment will begin. During the treatment you will hear the motor from the afterloader pushing and pulling the radiation source in and out of each of the channels of the applicator. You won’t feel or see the radiation being delivered. The treatment will take about 5-10 minutes. Once the treatment is done you will be disconnected from the afterloader and the applicator will be removed. This whole process takes about 1-1.5 hours.
The position of the hollow catheters will be confirmed on the CT scanner or with fluoroscopy prior to your treatment being delivered to ensure that nothing has moved out of place. If it has then minor adjustments will be made. Once this has been done you will be transported to the brachytherapy suite and the implant will be connected to the HDR remote afterloader. The doors will be closed (there is a camera and microphone in the room so you can communicate with us) and the treatment will then begin. During the treatment you will hear the motor from the afterloader pushing and pulling the radiation source in and out of each of the channels of the applicator. You won’t feel or see the radiation being delivered. The treatment will take about 10-15 minutes. Once the treatment is done you will be disconnected from the afterloader.