News | July 28, 2008

Redesigned Shielded Applicators Improve Safety, Effectiveness of Brachytherapy

July 29, 2008 - To treat cervical cancer, clinicians apply a high dose of radiation directly to diseased tissues, which may be administered using a device called an intracavitary brachytherapy applicator.

Imaging the treated areas using computerized tomography (CT) or magnetic resonance imaging (MRI) improves the effectiveness of treatments because the scans allow clinicians to accurately plan the radiation treatments. But when so-called "shielded" applicators, which contain metal shields to protect healthy bladder and rectal tissues from radiation exposure, are used to deliver these treatments, CT images exhibit distortion. Furthermore, the devices themselves are not compatible with MRI scanners.

A new design avoids those problems. The applicator was invented and developed by the faculty at the M.D. Anderson Cancer Center and evaluated by Ph.D. medical physics candidate, Michael J. Price or his dissertation work under the direction of Firas Mourtada, Ph.D. It is made out of special materials that makes it compatible with MRIs, and features a movable shield that both reduces the exposure of healthy tissues to radiation and permits the use of CT and MRI scans. Because the shield can be moved out of the path of the scanners' beams, the applicator can be used in conjunction with CT without distortion to the images. In addition, Price says, "the position of the shield can be adjusted as a function of specific patient anatomy," allowing clinicians to tailor treatments for each individual patient. Preliminary studies by the MD Anderson team show that the device may reduce the radiation dose to the rectum by 22 percent when compared to a commonly used CT/MRI-compatible intracavitary brachytherapy applicator.

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Source: American Association of Physicists in Medicine