IMRT & IGRT
What is Image Guided Radiation Therapy?
Image-guided radiation therapy (IGRT) is a type of conformal radiotherapy that allows higher doses of radiation to be given to the tumor while limiting the impact on healthy tissue. The method uses advanced imaging technology before and during radiation therapy to enhance the precision and accuracy of treatment delivery.
“Patients often ask us what image-guided radiation therapy is,” says Steven G. Lester, M.D., FACRO at Central Florida Cancer Care Center. “We use IGRT to be more precise on a daily basis because what we’ve learned over the last twenty years is that there’s more organ motion than many patients and physicians realize.”
How is Image Guided Radiation Therapy Used?
Precise tumor locations can shift as a result of normal, subtle movements in the body due to breathing, bladder, and bowel function. Image-guided radiation treats tumors situated on or near vital bodily structures prone to movement including the lungs, liver, and prostate.
“Organ motion is due basically to your breathing and the normal displacement of tissue,” explains Dr. Lester. “Take your prostate, for example. If your rectum is full (of volume), your prostate is going to move in a different direction than when it’s empty. You can be as still as you want (during treatment) but we need to account for those internal motions.”
IGRT is often used alongside intensity-modulated radiation therapy (IMRT), a method of advanced-precision radiotherapy that uses computer-driven x-rays to carry targeted radiation to a malignant tumor.
Before IGRT, doctors had to treat a larger area of the body just to be sure the cancer tumor was receiving the needed radiation. The expanded treatment area meant more damage to the surrounding healthy tissues.
“Before IGRT, the way we had to account for organ motion was with a bigger margin, treating more tissue,” says Dr. Lester. “IGRT allows us to precisely localize where the cancer and the normal tissue is right before treatment, so we’re able to treat a smaller volume.”
What Are the Advantages of IGRT?
Radiation therapy machines are equipped with imaging technology to allow your doctor to image the tumor before and during treatment. The images show the size, shape, and position of cancer as well as the surrounding tissues and bones. This can help:
- Deliver accurate doses of radiation
- Define, localize, and monitor tumor position, size, and shape before and during treatment
- Determine the possibility of greater and more precise radiation to enhance tumor control
- Lower the radiation exposure of healthy tissues around the tumor
“Image guidance assists us in giving patients the most precise treatment possible,” says Dr. Lester. “Now we’re able to treat a smaller area, which we hope creates fewer side effects and allows us to be just as effective but with less normal tissue being affected.”
A radiation oncologist puts together a patient’s treatment plan through a planning process, called a simulation session. Other imaging procedures might be used to determine the exact shape and location of the tumor further, and then the patient may be secured in place to help them stay in the correct position throughout the treatment.
Ultimately, state-of-the-art SmartBeam IMRT technology gives hope to cancer patients who would have been deemed untreatable just a generation ago. “The goal of image guidance is to assist us in giving you the most precise treatment possible,” says Dr. Lester.
Today, IMRT is employed to treat prostate, head and neck, breast, thyroid, and lung cancer, as well as tumors in the liver and brain, lymphomas, and sarcomas.
Central Florida Cancer Care Center features one of the most advanced forms of radiation treatment available delivered by the powerful Varian 23EX linear accelerator. This provides Intensity Modulated Radiation Therapy (IMRT) and Image Guided Radiation Therapy (IGRT). This complex technique of delivering radiotherapy is a powerful method of precisely delivering conformal doses of radiation to tumor tissue, while simultaneously sparing nearby healthy tissue. To plan and deliver IMRT/IGRT treatments, our centers use the SmartBeam IMRT, a state-of-the-art planning and delivery system designed by Varian Medical Systems.
SmartBeam IMRT uses computer-generated images to plan and then deliver tightly focused radiation beams to cancerous tumors. Clinicians use it to precisely “paint” the tumor with a customized radiation beam that conforms as closely as possible to the shape of the tumor.
SmartBeam IMRT can be used to treat tumors that might have been considered untreatable in the past due to close proximity of vital organs and structures. Currently, IMRT is being used to treat cancers of the prostate, head and neck, breast, thyroid and lung, as well as in gynecologic, liver, brain tumors, lymphomas and sarcomas.