Treatments and Technology

Image Guided Radiation Therapy


Overview


Image-guided radiation therapy (IGRT) is the use of frequent imaging during a course of radiation therapy to improve the precision and accuracy of the delivery of treatment.

In IGRT, machines that deliver radiation, such as a linear accelerator (for x-ray or photon) or cyclotron/synchrotron (for proton), are equipped with imaging technology so that the physician can image the tumor immediately before or even during the time radiation is delivered, while the patient is positioned on the treatment table. Using specialized computer software, these images are then compared to the images taken during simulation. Any necessary adjustments are then made to the patient’s position and/or radiation beams in order to more precisely target radiation at the tumor and avoid healthy surrounding tissue.

Computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), ultrasound (US) and x-ray imaging may be used for IGRT. Newer methods for IGRT use a non-radiation light-emitting diode (LED) light on the patient’s body surface or implanted magnetic transponder inside the patient’s body.

IGRT is used to treat tumors in areas of the body that are prone to movement, such as the lungs (affected by breathing), liver, and prostate gland, as well tumors located close to critical organs and tissues. It is often used in conjunction with intensity-modulated radiation therapy (IMRT), proton beam therapy, stereotactic radiosurgery, or stereotactic body radiotherapy (SBRT), which are advanced modes of high-precision radiotherapy that utilize computer-controlled x-ray accelerators to deliver precise radiation doses to a malignant tumor or specific areas within the tumor.

In IGRT, imaging equipment is mounted on or built into the machine that delivers radiation, such as a linear accelerator. Imaging equipment may also be mounted in the treatment room. Imaging technologies used in IGRT include x-rays, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), and ultrasound (US). Sometimes, IGRT is performed by a special camera in the room that emits LED light and tracks the patient’s body surface. For selected areas affected by breathing, a special small device is placed on the patient’s chest or abdomen that emits light. This gives feedback regarding the respiratory stage.

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