A highly precise form of radiation therapy allows medical specialists to zero in on certain types of cancers.
IMRT is an advanced mode of radiotherapy that uses computer-controlled linear accelerators to deliver precise radiation doses to malignant tumors, or even to specific areas within a tumor, said Paul Mandelin, D.O., radiation oncologist at Marshfield Clinic Weston Center.
“We typically use it for head and neck, and prostate cancers,” Dr. Mandelin said. “Those are two applications where the technology is rapidly advancing. It depends on the location, the tumor site and the patient.” IMRT is not appropriate for all cancer patients.
IMRT allows the radiation oncologist to adjust the radiation dose to conform more precisely to the three-dimensional shape of the tumor by modulating – or controlling – the intensity of radiation beams from multiple directions. The precision allows higher radiation doses to be delivered to the tumor while minimizing side effects and damage to surrounding normal tissues.
The treatment is carefully planned by using 3-D computed tomography (CT) with the ability to add in magnetic resonance (MR) or positron emission tomography (PET) images of the tumor. All this information can be used with computerized dose calculations to determine the best dose intensity pattern.
“IMRT is improving cancer treatment because with more accurate tumor localization we are able to give more treatment to a smaller area, which equates to better long-term control and fewer side effects,” Dr. Mandelin said. “With conventional radiation therapy, we had to treat bigger fields, and critical organs could get in the way.”
In addition to head, neck and prostate tumors, IMRT has been used in limited situations to treat breast, lung and gynecologic cancers as well as gastrointestinal tumors and certain types of sarcomas.
Although IMRT has been in use for about a decade, newer machines and faster computers offer more precise beam control with shorter treatment times compared to the original IMRT technology.
