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Conformal radiation: Making radiation oncology an exact science

Cancer treatment
08/28/2004

New technology has taken some of the guess-work out of treating cancer patients with radiation. The premise behind radiation treatment is simple: Target the cancer with the amount of radiation necessary to eradicate the cancer. The problem arises, however, in sparing the normal surrounding structures from damage.

"We want to treat the cancer with as much radiation as necessary while keeping patient complications to a minimum," said Robert Murray, MD, radiation oncologist at Moses Cone Health System Regional Cancer Center. "If we can limit the radiation to just the cancer and not to surrounding structures, we can apply more radiation to better treat the cancer."

In traditional planning, radiation oncologists used a series of CT scans and X-rays to estimate where the tumor is and where the radiation should be administered. The difficulty, however, is that because both images are two-dimensional, the physician is unable to get a complete picture of the cancer and surrounding organs. This has meant that radiation is extended to encompass surrounding normal tissue to ensure complete treatment of the cancer.

In conformal radiation, special computer software creates a 3D image of the cancer and surrounding organs. This provides a complete picture of the radiation site and allows direct targeting of the cancer with minimal spill-over into the surrounding tissue. This, therefore, allows the radiation oncologist to better visualize the cancer, and thus, treat the patient with fewer complications.

"With traditional planning, we could be accurate. Now, with 3D technology, we can be more precise," said Murray.

Creating the 3D model is a complicated process that takes between six and eight hours. As with normal radiation planning, the process begins with a CT scan. The image is then loaded into the computer, and a dosimetrist identifies the body structures and builds a 3D model by stacking the images from the CT scan on top of each other.

Once a 3D computer image is created, the radiation oncologist and the dosimetrist can determine the suitable treatment plan. Because a better image of the anatomy is available compared to that of traditional planning, a higher dose of radiation can be used without threatening surrounding structures. The computer also displays the exact amount of radiation affecting the different areas of the cancer and surrounding tissue.

"Because we can see the entire structure and not just a slice from the CT scan, we can pinpoint where treatment should be administered," said Murray.

According to Murray, many patients with different types of cancer will benefit from Conformal Radiation Therapy.

August 27, 1998

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