FDA offers guidance on lowering CT dose

Nov 5, 2001

The U.S. Food and Drug administration has issued a notification emphasizing the importance of keeping radiation dose during CT procedures as low as reasonably achievable, "especially for pediatric and small adult patients, who may sometimes receive more radiation than needed to obtain diagnostic images," the agency said.

The notification stresses the importance of adjusting CT scanner parameters appropriately based on a patient's weight and size, as well as the anatomic area being scanned. Because exposure latitude is so wide with CT, overexposure which might render radiographic images unusable can still be read on CT images, enabling doctors to ignore the problem.

The document recommends that CT settings be optimized by:

Reducing tube current. "With all other factors held constant, patient radiation dose is directly proportional to x-ray tube current," the notice stated.
Using charts or tables of tube-current settings based on patient weight and size, and anatomic regions of interest.
Increase table increment (axial scanning) or pitch (helical scanning).

The document also recommends that doctors reduce the number of multiple scans with contrast material by eliminating precontrast scans when medically appropriate. Finally, the agency recommends the elimination of inappropriate referrals for CT.

"In some cases, conventional radiography, sonography, or magnetic resonance imaging (MRI) can be just as effective as CT, and with lower radiation exposure," the FDA wrote.

The November 2 Public Health Notification is available on the Internet, at http://www.fda.gov/cdrh/safety/110201-ct.html .

By Eric Barnes
AuntMinnie.com staff writer
November 6, 2001

FDA draft impact assessment of Federal Performance Standard for Diagnostic X-ray Systems, August 15, 2001

Low-dose CT fluoroscopy minimizes interventional exposure, July 30, 2001

FDA's radiation concerns may lead to dose displays for scanners, May 22, 2001