IMRT Radiation: What Is It?

IMRT radiation, which is also called Intensity modulated radiation therapy, has revolutionized cancer care by giving the ability to radiation doctors to deliver radiation to the target area while minimizing damage to surrounding normal tissues.
Prior to the introduction of IMRT radiation, radiation doctors utilized a technique called 3 dimension treatment planning technique. This involved delivering a calculated amount of radiation through two or four different directions aimed at the area of the body containing cancer. The radiation beam was shaped to conform to the contour of the target as seen from each angle of entry of the beam. But there was no way that the beam would conform precisely to the target area and at least a part of a vital structure located close to the target volume would receive the same amount of radiation as the target. This limited the ability of radiation doctors to deliver higher, more effective doses of radiation to the target volume. This was especially important in such situations as prostate carcinoma where the dose to the adjacent part of the rectum caused horrendous long term side effects such as bleeding, stricture and frequent bowel movements. Sometimes these side effects required surgical procedures to correct the problem. Other areas where 3 D treatment planning and delivery caused problems was in the treatment of cancers in different areas of the head and neck. Poor ability to control radiation to the salivary glands, spinal cord and other vital structures resulted in long term disabling side effects and poorer rate of control of these cancers.
IMRT radiation came into main stream practice in the treatment of cancer because of the entry of powerful computers into the medical field. The radiation doctor now had the capacity to outline very precisely the target volume and the surrounding normal structures and dictate to the computer the amount of radiation that he would allow for each of these areas and the volume of these organs that were allowed a certain amount of radiation. The treatment planning computer would now go through multiple calculations sometimes lasting for hours while modulating the intensity of radiation through each entry point into the patient. Modulation of the beam is performed by the movement of metallic leaves that go in and out blocking and unblocking the exit of radiation from the head of the radiation machine. Thus, different areas of the target volume would get different intensities of radiation from each beam entry. The sum result of multiple beams entering the patient from different angles would result in radiation dose literally painted very precisely over the target volume while giving the radiation physician the amount of radiation that he has allowed to vital organs located close to the target.
In simple terms, 3 D treatment planning and delivery is the same as carpet bombing an entire block in a city while IMRT radiation is the equivalent of a smart bomb that would hit precisely the exact building in that block while leaving the adjacent buildings relatively unscathed thus sparing innocent lives while annihilating the bad guys in the target building.
IMRT radiation technology is utilized to treat cancers located deep within the body, are irregular in shape and are adjacent to vital structures. Good examples are prostate cancers, head and neck cancers, pancreatic cancer and tumors in the brain among several others.
Patients who are exploring radiation therapy as an option in the treatment of their cancer will do well when they are fully informed. They should not hesitate to ask their cancer radiation doctors regarding the age and the technology utilized to treat them.