A new software program that enhances the quality of CT images allowed doctors to cut in half the radiation dose needed for a colon scan and still produce clear images, U.S. researchers said on Monday.

A series of recent studies has suggested that computed tomography or CT scans can increase a person's lifetime risk of cancer, especially younger people who have multiple scans.

This new technique allows us to use far less radiation than even a typical abdominal CT scan without compromising image quality, said Dr. Daniel Johnson of the Mayo Clinic in Scottsdale, Arizona, whose study appears in the American Journal of Roentgenology.

CT scans of the colon, sometimes called a virtual colonoscopy, are meant to replace the more invasive test in which a camera is inserted into the rectum and threaded through the colon to look for signs of cancer.

The scans have been shown to be effective, but concerns about radiation exposure have scared many doctors off.

One of the reasons people say not to get a virtual colonoscopy is because of radiation dose. This is a method you could use to minimize that concern, Dr. Amy Hara of Mayo, who worked on the study, said in a telephone interview.

The fact that we can now screen patients with an increasingly lower dose can allay concerns, attract more patients to be screened and ultimately save tens of thousands of lives each year, Johnson said in a statement.

Medical equipment makers General Electric, Siemens AG and Philips have been working on ways to reduce the amount of radiation required to produce an image.

Johnson studied a technique launched by GE in 2008 called Adaptive Statistical Iterative Reconstruction or ASIR.

The software allows radiologists to reduce the noise or fuzz in an image, making for a clearer picture with less radiation. The team studied image quality using both standard and reduced radiation doses in a phantom or dummy colon and in 18 patients.

They saw no significant difference in image quality between the patients who got the test with the standard dose, and those who got less radiation with the ASIR technique. And the phantom study showed much less fuzz when images were made with ASIR.

GE provided the software for the study. Hara said other equipment makers are testing similar products, but so far, GE appears to be in the lead with the technology.

In May, researchers at the International Society for Computed Tomography conference in San Francisco presented the first results of studies using GE's next-generation version of ASIR, which may allow doctors to cut the radiation dose by 80 percent, the company said last month.

(Editing by Maggie Fox and Todd Eastham)

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