What is Intensity Modulated Radiation Therapy (IMRT)?
Intensity modulated radiation therapy (IMRT) is an advanced type of high-precision radiation therapy. It uses computer-controlled linear x-ray accelerators to deliver precise doses of radiation to the patient’s malignant tumors. This type of therapy allows the radiation dose to be more precisely tailored to the three-dimensional shape of the tumor by modulating the intensity of the radiation beam. Likewise, this treatment also allows higher doses to be focused on regions within the tumor, minimizing radiation exposure to healthy areas. Hence the importance of the three-dimensional study and magnetic resonance imaging (MRI) of the patient, to determine the dose intensity pattern best suited to the tumor.
Why is it performed?
Intensity-modulated radiation therapy is used to treat cancers, basically of the prostate, head and neck, and the central nervous system. However, it has also been used in some cases to treat breast, thyroid and lung cancer, as well as gastrointestinal and gynecological tumors and sarcomas. Some studies show that it may also be useful in treating some pediatric cancers.
This type of radiation therapy prevents cancer cells from dividing and growing, which slows tumor growth and may even stop it. In fact, in many cases this type of radiation therapy is able to kill all the cancer cells.
What is Intensity Modulated Radiation Therapy (IMRT)?
Intensity-modulated radiation therapy uses advanced technology to manipulate radiation beams with photons or protons that adapt to the shape of a tumor.
Intensity-modulated radiation therapy uses several small beams of photons or protons with different intensities that are precisely irradiated onto a tumor. The radiation intensity of each beam is controlled, and the beam shape is different for each treatment.
The goal of intensity-modulated radiation therapy is to match the radiation dose to the target and to avoid or reduce exposure of healthy tissue to limit the side effects of treatment.
Preparing for IMRT (Intensity Modulated Radiation Therapy)
Before any treatment planning, a complete physical examination and medical history review should be done. This is followed by a treatment simulation session, in which a CT scan is performed. Sometimes a small mark is made on the patient’s skin to help align and aim the equipment.
The radiation oncologist uses this scan to create an individual plan for each patient. In some cases, a mask may be used to keep the patient comfortable during treatment. Sometimes the patient is instructed to follow certain bowel and bladder preparation regimens, or to fast before the treatment simulation.
In addition, intravenous contrast material may be injected during the CT scan to help better define the tumor. Sometimes other diagnostic procedures, such as positron emission tomography (PET) or magnetic resonance imaging (MRI) may be necessary for IMRT planning.
These diagnostic images can be combined with the planning CT and help the radiation oncologist determine the exact location of the tumor. It is also advisable to insert radiodense markers within the target area for more precise positioning.
Generally, IMRT sessions begin approximately 1-2 weeks after simulation.
Aftercare after the procedure
As with other radiation therapy treatments there is usually no pain during treatment. However, it is possible to stop the machine if the patient experiences discomfort due to the treatment position or positioning devices.
As treatment progresses, some patients may experience certain treatment-related adverse effects. The nature of these depends on which normal tissue structures near the tumor are being irradiated.
Side effects of radiation therapy include problems that occur as a result of the treatment itself as well as damage done by the treatment to healthy cells in the treatment area. The number and severity of side effects you experience will depend on the type of radiation, the dose prescribed and the part of the body being treated.
Side effects from this radiation therapy are usually early and delayed, in that they occur during or immediately after treatment and usually disappear within a few weeks, and common early side effects that include tiredness or fatigue and skin problems.
The skin in the treatment area may become more sensitive, red, irritated or swollen. Other skin changes include dryness, itching, peeling and blistering. Depending on the area undergoing treatment, other early side effects may include:
- Hair loss in the treatment area.
- Mouth problems and difficulty swallowing.
- Eating and digestion problems.
- Diarrhea.
- Nausea.
- vomiting
- headaches
- Tenderness and swelling in the treatment area.
- Urinary and bladder changes.
Delayed side effects, which are rare, occur months or years after treatment and are often permanent. They include:
- Brain changes.
- Spinal changes.
- Lung changes.
- Liver changes.
- Colon and rectal changes.
- Infertility.
- Joint changes.
- Lymphedema.
- Changes in the mouth.
- Secondary cancer.
There is a small risk of developing cancer from radiation therapy. After radiation therapy for cancer you will be evaluated regularly by your radiation oncologist for complications as well as recurrent and new cancers. Thanks to techniques, such as IMRT, radiation oncologists maximize the cancer-destroying capabilities of radiation therapy while minimizing its effects on healthy tissues and side effects on organs.