Analog to Digital: The Role of the Film Digitizer

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X-ray film digitizers are enablers - integrating prior films into a PACS environment, increasing productivity for radiology practices and permitting remote radiology and image sharing functions where analog images from film-based centers or modalities must enter the digital domain. With the help of a DICOM network to store, retrieve and move images for the clinicians' use, digitizers play a vital role in uniting the analog to the digital world.


Inland Imaging's staff of 45 radiologists in six locations read x-ray images for outlying rural hospitals 24x7, says Jon Copeland, chief information officer for Duvoisin & Associates that manages Inland Imaging. What is the enabler? About 20 digitizers.

"Because these image data sets are large [10-13 megabytes apiece], we require a T1 line or higher speed digital network," explains Copeland. At any given time, they can have 20 to 25 radiologists reading films in six or seven locations.

With this system, the outlying hospitals are not required to maintain radiologists on staff, and patients benefit from having sub-specialist radiologists to read their films. "If it's a neuro case or a musculoskeletal case, we can send that image to a fellowship-trained radiologist who specializes in those images," concludes Copeland.

Besides providing these services to outlying communities, they have incorporated digitizers (the Array 2905) into each of their four imaging centers. If a patient brings films to the center, they process the images at the front desk and return the originals to the patient. Films are not kept in the centers.

Thomas J. Nardozzi, president of Array Corp., describes another application for digitizers at image storage sites that serve as the repository for older films. A storage service can scan images and send them to print in the radiology department or to be read as soft-copy on a radiology workstation.

"The predominant use we see for our scanner is for relevant priors," says Nardozzi. "It makes no sense for a radiologist to be reading soft-copy images with great display on a workstation, and then have to look at older films on a lightbox." From a productivity standpoint, having all images available in digital format improves the time management for busy radiologists.

Brad W. Smith, PACS manager for Baptist Memorial Health Care Corp. in Memphis, uses digitizers (Array 2905 units) in the radiology department file rooms of each of the 15 hospitals in their system. He reports that they have found the digitizers easy to install, support and use. They use the devices, with an auto-feed system, to copy films for referring physicians while forwarding the digital images into their PACS.

Besides direct clinical applications, the digitizers are used to create teaching files, once patient identifiers are stripped from the image data sets. "Outside the realm of DICOM, they can export images in a wide variety of file types, from DICOM jpgs in or out of compression, TIFF files or raw files for research," Nardozzi says.

Additionally, using standard system software, they can burn images to a CD, including appropriate HIPAA warnings, for a patient to take to a referring physician. The resulting images on the CD can be visualized on any standard computer because a viewer is included in the package.

Most of the digital images created for remote radiology or teleradiology purposes, such as chest x-rays or gross anatomy studies that are scanned in 2K format (2,000 pixels on the long axis of the image) with three line pairs per millimeter (lp/mm) that can be transmitted over regular phone lines.

Orthopedic cases are usually scanned at 4K, which is higher resolution than most CR, according to Todd Minnigh, senior marketing manager for CR and DR for Kodak's Health Imaging Group. The Kodak LS75 scans up to 4K, which refers to greyscale resolution from a density perspective.

Kodak digitizers use a laser to scan through the film, and then they use a multiplier similar to that on a CR device, to create a digital image, explains Minnigh. "This results in accuracy in density in the duplicate and a good penetration of light." When reading soft-copy, the radiologist wants the best possible separation of greyscale and shadow.

Another application where film digitizers have proven their value is in mammography, where prior films are digitized at 8K (11.75 lp/mm) to produce appropriate resolution for breast cancer diagnosis.

"One 8x10 or 18x24 mammogram is roughly 38 megabytes