Analog to Digital: The Role of the Film Digitizer

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.


FACILITATING PRACTICE

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 at 8K, and there are four images they need to read," says Janet Sterritt, vice president, medical products for Howtek Devices. Considering that a mammography clinic could have up to six machines running daily, they could generate terabytes of information every day. IT departments must develop networks that can manage the high volume of data produced.


IMPORTANT DESIGN FEATURES

Film digitizer vendors have worked to improve the capabilities of their devices in a variety of ways.

Vidar Systems serves as the digitizer supplier to all of the major imaging and CAD vendors as well as PACS developers.

Brian Beardslee, vice president of sales and marketing for Vidar, suggests that the reliability level of their devices is what drives their adoption by so many vendors. Their warranty calls for replacement if something should go awry.

"We include Automatic Digitizer Calibration Routines as firmware that resides within the digitizer," explains Beardslee. The Diagnostic Pro Advantage Film Digitizer features an internal prompt for the device to calibrate automatically before each film is digitized, which eliminates user intervention for this task. Because a batch of up to 25 mixed-size films can be loaded into the machine and digitized two times faster than previous models, this feature is designed to provide a reliable end product.

Fujifilm Medical Systems USA includes Vidar digitizers as a component in their Synapse PACS. Bill Urban serves as the product manager for network systems at Fujifilm, and reports the Vidar products are quite reliable.

"Most of the RFPs request a digitizer solution, so we consider it to be a valuable and necessary portion of our Synapse portfolio," says Urban.

Steve Haas, vice president of sales and marketing for iCRco in Torrance, Calif., describes their hybrid CR (computed radiography) with integrated film digitizer system, the CR 2000. Built on the film digitizer pipeline called Cobrascan from RDI, this system offers two-products-in-one, thereby placing the CR scanner and digitizer in one room. If the patient brings old films, the technologist can scan them in at the point of examination, and push the images into the PACS.

"The other benefit to this system is that the radiologist derives value from having common algorithms for processing both studies," explains Haas. Post-processing procedures employ different algorithms to suppress, subtract or enhance certain structures to provide additional information in reading the soft-copy. This has proven valuable in radiation therapy planning where they take scanned films, apply the algorithms and further enhance the diagnostic quality depending on how the data set is handled. These activities provide latitude of diagnostic capabilities rather than just a static impression of the film, according to Haas.

Array's Nardozzi describes a feature for the 2905 that addresses added productivity. "With auto-divide, we can take an MR or CT film that has 12-on-one, or 15-on-one slices, and we can auto-divide that film to become separate DICOM images," he says. "This means that as radiologists sit in front of their workstations, they can look at MR slices in stack mode."

Howtek's Sterritt describes their new product, the Fulcrum film digitizer, which is designed to be used with third-party computer-assisted detection (CAD) systems for mammography.

"There are new films developed by Kodak, Agfa and Fuji that raised the optical density," explains Sterritt. Film used to be graded below 4.0 optical density (OD), but they have now evolved to 4.2 OD. They have re-designed the sensor completely, called a Contact Imaging Sensor (CIS), that runs the full width array.

With CCD technology, a system of lenses and mirrors focuses the full width of a 14-inch image onto a one-inch wide chip, resulting in some areas with aberrations. Howtek designed a sensor that runs the full width of the film area on this non-traditional scanner. "The good news is that we now go up to 12 line pairs /mm, which is the top end of resolution, and we go up to 4.4 optical density…and it does it twice as fast as our other family [of systems] does," says Sterritt.


WHAT DOES AN IT PROFESSIONAL NEED TO KNOW ABOUT FILM DIGITIZATION?

Kodak's Minnigh says, "Look at the digitizer much the same way you would look at a CR system. You want your database to be clean, so you'll want DICOM worklist management on the digitizer so you can identify these images. You'll want DICOM store so you can output them, and DICOM print so you can print them."

Array's Nardozzi advises IT personnel to be involved in decision-making about which films should be processed, because the resulting digital images will reside in the short and long-term storage system.

"Attrition will take care of a great number of the files, and they should only do [films] of patients who are coming through the door, and not the entire catalog of images from the preceding 5 to 7 years," says Nardozzi. He notes that it doesn't make economic sense to process all of the old priors.

IT professionals are critical members of the team involved in film management. They must be involved in decision-making processes that determine which films will be scanned on the digitizer, and what will happen to those images.