Intensity Modulated Radiation Therapy
Greater Baltimore Medical Center (GBMC) is the first community hospital in the area and one of very few hospitals nationwide to offer the sophisticated Intensity Modulated Radiation Therapy (IMRT) technology to oncology patients. The first patient recently completed seventeen treatments, which began on October 19, 2001.
"IMRT is radiation therapy," explains Robert Brookland, MD, Chairman of GBMC's Radiation Oncology, "with a very advanced delivery. The radiation beam that normally comes from an accelerator is a uniform dose in a flat field. With IMRT, we are able to modulate the intensity of that beam so different areas of the treatment field get varied amounts of radiation and ultimately optimize the dose distribution."
For patients with cancers of the prostate, head and neck, and those that are near critical normal tissues and organs, IMRT allows patients to be treated with higher doses of radiation to the cancer and lower doses to normal tissues. "This," states Dr. Brookland, "increases the chances for greater cancer cells to be destroyed while decreasing chances for injury to normal tissues."
IMRT shapes the treatment field by modulating the radiation intensity along the path of the beam. It is a very customized distribution of the radiation dose. IMRT allows treatment of a tumor adjacent to a critical structure, such as the spinal cord, while still protecting the normal tissue in a way that standard technology does not always permit.
Preparation for IMRT included the addition of multi-leaf collimation (MLC) to Radiation Oncology's technological arsenal. A sophisticated computer-generated blocking technology, MLC replaces the use of lead blocks to protect normal structures during radiation treatments. The collimator generates digital blocks for the accelerator in just a few minutes time.
The first IMRT patient treated at GBMC was a man with prostate cancer. The IMRT field was started after he completed treatment to a larger area. The "boost" treatment used IMRT to take the prostate itself to high dose, limiting the dose to the patient's uninvolved normal adjacent tissues. The patient's course of IMRT cancer treatment included seventeen treatments, which began on October 19, 2001 and were completed in early November.
A treatment field of the prostate, represented by the red line, showing how parts of the field receive different doses of radiation.
