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High doses of radiation have been proven to kill cancer cells and to shrink
tumors. Intensity Modulated Radiation Therapy (IMRT), uses x-rays of varying
intensities along with computer generated images to plan and deliver highly
targeted radiation directly to cancer cells while significantly reducing
the amount of radiation to surrounding healthy tissue. This technique
is the most precise form of radiation therapy available today, and can
increase the rate of tumor control by conforming to the shape of the tumor
while minimizing adverse side effects. Because of its extreme accuracy,
tumors which were formerly considered untreatable because of their proximity
to vital organs can now be controlled.
A computer program optimizes the treatment plan based on the physician's
instructions as relates to dose, and tumor size, shape, and location.
The radiation is then delivered by a machine called a medical linear accelerator,
equipped with a special device called a multileaf collimater which shapes
the radiation beam, and delivers it in accordance with the treatment plan.
This equipment can be rotated around the patient sending beams as small
as the size of a pencil tip and of varying intensities to the tumor at
preferential angles.
In a treatment planning session, semi-permanent ink is often used to mark
the patient's skin, to assist in aligning the radiation equipment with
the targeted area. A CT scan may be used to generate three-dimensional
diagnostic images of the patient and to determine the dose of radiation
the tumor will receive. On the day of the treatment, the patient is positioned
on a treatment table, and the process begins. Since external radiation
is essentially like having an x-ray taken, the patient will not see or
hear the radiation being administered, and the procedure will be painless.
Journal article on IMRT for malignant mesothelioma