Intensity Modulated Radiation Therapy (IMRT)

The University of Maryland Marlene and Stewart Greenebaum Comprehensive Cancer Center has helped perfect IMRT treatment by developing Direct Aperture Optimization, or DAO.

What is IMRT?


Using DAO radiation from seven beam directions, the tumor is targeted while sparing surrounding normal tissues.

Intensity Modulated Radiation Therapy, or IMRT, is considered the most advanced photon beam radiation therapy available to destroy cancer cells without damaging normal tissue. IMRT uses varying beam intensities to send radiation to the tumor site from the most favorable paths. This method of radiation therapy allows higher doses of radiation to be delivered to the tumor while minimizing damage to surrounding vital organs. This type of radiation has become an option for patients who may not have been candidates for radiation in the past because their tumors were located near vital organs.

Recognized as a national leader in IMRT, the University of Maryland Greenebaum Comprehensive Cancer Center has helped perfect this method of treatment by developing Direct Aperture Optimization, or DAO. This is an IMRT planning technique that dramatically reduces treatment time. It also increases patients' comfort and helps ensure that they remain still and therefore receive the most effective dose of radiation, right at the site of the tumor.

How does IMRT work?

Conventional radiation therapy techniques use radiation beams of uniform intensity to destroy the tumor cells in a patient's body. Although the tissues outside the radiation field can be protected by shaping the radiation beam to encompass the tumor, a column of tissue from the beam's entrance to its exit is indiscriminately irradiated.

Using the fact that not all tissue reacts to radiation in the same way, IMRT varies radiation intensity across the field. The radiation beam can also rotate around the patient, sending beams from a more favorable angle and location. By cross-firing the tumor with these beams of varying intensity from all possible angles and locations, a uniform dose of radiation is delivered to the tumor, while the effects on the sensitive structures surrounding the tumor are minimized.

During the IMRT treatment planning process, a computer-generated planning system acquires information about the location of the tumor and its surrounding structures from a patient's CT images. The computer maps the optimal angles and locations, and higher beam intensities are then assigned to these angles and locations. Once the treatment plan is generated, the computer sends it to the radiation machine to deliver the treatment.

What types of tumors are being treated with IMRT?

Because almost all tumors are surrounded by healthy tissues, IMRT can be applied to virtually any part of the human anatomy. The benefits of enhanced tumor control and reduced damage to normal tissue can be realized for most tumors suitable for radiation treatment, regardless of their size and shape.

What are the side effects of IMRT?

Because the radiation is sent to the tumor only through allowed paths, the side effects of IMRT, if any, are much less than with conventional treatment methods. The treatment is administered mostly on an outpatient basis. After the completion of treatment, most patients can resume their normal daily routine.

IMRT involves the latest technology, advanced equipment and a group of very knowledgeable doctors. The Radiation Oncology Department at the University of Maryland Greenebaum Comprehensive Cancer Center is dedicated to serving the needs of the Maryland community and providing hope to cancer patients and their families.

For more information, contact the Department of Radiation Oncology at 410-328-6080.