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| What is Intensity-Modulated Radiation Therapy and how is it used? |
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Intensity-modulated radiation therapy (IMRT) is an advanced mode of high-precision radiotherapy that utilizes computer-controlled x-ray accelerators to deliver precise radiation doses to a malignant tumor or specific areas within the tumor. The radiation dose is designed to conform to the three-dimensional (3-D) shape of the tumor by modulating-or controlling-the intensity of the radiation beam to focus a higher radiation dose to the tumor while minimizing radiation exposure to surrounding normal tissues. Treatment is carefully planned by using 3-D computed tomography (CT) images of the patient in conjunction with computerized dose calculations to determine the dose intensity pattern that will best conform to the tumor shape. Typically, combinations of several intensity-modulated fields coming from different beam directions produce a custom tailored radiation dose that maximizes tumor dose while also protecting adjacent normal tissues.
Because the ratio of normal tissue dose to tumor dose is reduced to a minimum with the IMRT approach, higher and more effective radiation doses can safely be delivered to tumors with fewer side effects compared with conventional radiotherapy techniques. IMRT also has the potential to reduce treatment toxicity, even when doses are not increased. |
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Currently, IMRT is being used to treat cancers of the prostate, head and neck, breast, thyroid and lung, as well as in gynecologic, liver and brain tumors and lymphomas and sarcomas. IMRT is also beneficial for treating pediatric malignancies.
Radiation therapy, including IMRT, stops cancer cells from dividing and growing, thus slowing tumor growth. In many cases, radiation therapy is capable of killing cancer cells, thus shrinking or eliminating tumors. |
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| Who will be involved in this procedure? |
Most facilities rely on a specially trained team for IMRT delivery. This team includes the radiation oncologist, medical radiation physicist, dosimetrist, radiation therapist and radiation therapy nurse.
The radiation oncologist, a specially trained physician who heads the treatment team, sets an individualized course of treatment with the help of the radiation physicist, who ensures the linear accelerator delivers the precise radiation dose and that computerized dose calculations are accurate. A dosimetrist, under the supervision of the medical radiation physicist, calculates the IMRT exposures and beam configurations necessary to deliver the dose prescribed by the radiation oncologist. A highly trained radiation therapist positions the patient on the treatment table and operates the machine. The radiation therapy nurse provides the patient with information about the treatment and possible adverse reactions. |
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| What equipment is used? |
| A medical linear accelerator generates the photons, or x-rays, used in IMRT. The machine is the size of a small room-approximately 10 feet high and 15 feet long. The patient lies on the treatment table, while the linear accelerator delivers beams of radiation to the tumor from various directions. The intensity of each beam's radiation dose is dynamically varied according to treatment plan. |
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