Intensity Modulated Radiation Therapy
What is Intensity Modulated Radiation Therapy?
Intensity Modulated Radiation Therapy (IMRT) is an advanced type of three-dimensional radiation that is able to more precisely target the intended cancerous tissues. IMRT uses small beams to attack a tumor from different directions with varying intensity, minimizing the effects on healthy tissue. As the name suggests, the benefit of this delivery method of radiation therapy is the capability of modifying the amount or intensity of radiation delivered to different areas of the treatment area.
Prior to IMRT, radiation technology used large portals, or windows, and offered no ability to view or define the shape of the target or normal tissues in 3-D. Thus, treatment was usually delivered in an imprecise way, exposing healthy tissues to unnecessary radiation.
IMRT breaks those large windows into 40 small windows, which open and close as they rotate around the patient in an arc. With the precision of the radiation, the IMRT is able to greatly minimize exposure to the surrounding
healthy tissue and organs and maximize the intensity of the radiation to the cancer.
What are the advantages of Intensity Modulated Radiation Therapy?
The IMRT is the considered the ideal form of treatment by many
radiation oncologists because of its accuracy and powerfulness. A series of IMRT treatments can be anywhere between 4 to 8 weeks. Advantages of the IMRT include minimized side effects, minimized radiation to healthy tissues, higher radiation dosage to cancerous cells and shorter treatment duration.
How does Intensity Modulated Radiation Therapy work?
CT scans are taken of the patient and transferred into a treatment planning system. The target volume and normal tissues are contoured in three dimensions. In older forms of therapy, the entire tumor and small amount of healthy tissue would then be radiated with the same amount and intensity of radiation throughout.
In IMRT, however, the radiation oncology team (physician, physicist, and dosimetrist), determines the shape and amount of radiation to be delivered to any given point in the treatment area. The radiation oncology team has a greater control over the amount of radiation delivered to any given spot on or near the tumor. Since tumors are irregularly shaped, and different healthy tissues have varying tolerances for radiation, it makes sense that radiation would be delivered in different intensities to different areas. As a result of greater control over the intensity of radiation, side effects of the
radiation treatment are minimized while actually allowing the
radiation to focus more intensely on areas where needed.
