Low-budget digitizing solution focuses on digital cameras

Off-the-shelf digital cameras can be used as a low-budget teleradiology solution to digitize film, according to a poster presented at the Society for Computer Applications in Radiology meeting last month.

"In scenarios needing only comparison to diagnose digitally generated images, digital cameras offer a fast, cheap alternative to classic film scanners," said Dr. Yaron Rado of the University of Duesseldorf in Germany.

Rado was looking for an inexpensive way to digitize conventional x-ray film into the university's PACS database in order to compare foreign studies on film with studies taken in a filmless environment.

"We compared the ability of digital cameras to capture radiographs," Rado said.

Using the American College of Radiology standard for teleradiology as a reference, Rado measured the capturing abilities of camera from consumer to professional level in a price range of $500 to $5000. A Vidar Diagnostic Pro film scanner was used as the gold standard (600 dpi/16 bit) for comparison.

"Modern digital cameras fulfill the technical requirements of the ACR teleradiology standard," Rado said. "But to deal with the high optical density of x-rays, bracketing is necessary."

All the digital cameras tested (CoolPix 995, Canon D30, Nikon D1X) met the ACR requirement of small image resolution (greater than 1024 x 1024 pixels) and can resolve greater than 2.5 line pairs per millimeter on 10 x 12-inch film. They can capture the required color depth (8/10 bit) and therefore fulfill ACR requirements from the technical point of view, he said.

"However, the captured image's quality was insufficient for our purposes because the high optical density of conventional x-rays is too high," Rado said.

The solution he found is the classical photographic technique of bracketing, which over- and underexposes an image to spread the available capturing ability into the lighter and darker zones of an image.

"Using that technique, a picture quality comparable to that of the Vidar scanner was achieved," he said.