A nuisance. Thing of the past. Dead stuff walking. You hear it every day, in all its colorful variations. But despite the digital revolution and soothsayers’ warnings of its imminent demise, film is still everywhere.
Not only is film alive and well, but it seems to be thriving. The latest film products give electronic imaging a serious run for its money, while the new dry media are stealing major turf from wet formats. Film may not be anything new, but it certainly isn’t boring.
Forever yours
“Film is never going to go away,” says Janet Sterritt, V.P. of medical products at Howtek Devices Group (in Nashua, N.H., a division of iCAD, Inc.). “There’s a section of the market share of what film does that’s never going to be replaced. The final films, which are 36 inches long — there’s no CR or DR to do that. Then there are special-sized films that CR and DR haven’t been bothered to go after yet. Spinal films are something I don’t see anybody making a move to replace.”
Another area that continues to be dependent upon film, all vendors agree, is mammography. “FFDM [full field digital mammography] is coming on strong,” says Sterritt, “but the truth is that film’s got the same resolution, if not better, than FFDM has, and FFDM is very expensive. Look at the installed base on film products; it’s easier for people to switch from one film to a better film than it is for them to switch to a different technology.”
One more factor in film’s favor, says Sterritt, is that current CR and DR may never be adequate for mammography. “Mammography film captures imaging up to about 12 lp/m; CR, DR and FFDM are only about 9-10 lp/m. The newer films that were announced in December can go up to 15 lp/m. That says that with digital modalities, you’re not seeing as fine a microcalcification and you’re not catching it early. Mammography’s all about early detection, and film is still running ahead of the game.”
Sterritt points to emergency departments as another stronghold of film use, for two main reasons: Some accident injuries, heart attacks, and pediatric cases can’t be adequately imaged with CR, and many hospitals have limited equipment budgets.
“If an ER advertises that it can support accidents, it needs to be able to take skull and spine shots. CR and DR aren’t really at a level that shows hairline fractures of the skull, and they can’t do the spine in one shot.”
Pediatric emergencies also are better served by x-ray, says Sterritt. “The resolution in CR and DR isn’t suitable for hot-belly cases in small babies because it’s well below the resolution of film and digitized film. The causes of hot belly [i.e., intestinal tract blockages] tend to be very, very dark, very small objects. CR is about half to two-thirds where it needs to be against the FDA regulations on what’s acceptable for scanning that.”
Film therefore looks to remain a staple in facilities with limited budgets, says Sterritt, as they’re likely to prefer do-it-all equipment out of necessity. “A little community hospital only has to make an investment in one thing if it chooses x-ray for its ER. As far as a standard piece of gear that can get you a whole bundle of different uses, film is the best.”
Old dog/new tricks
A lot of people have misconceptions about analog imaging, says Bob Dickerson, senior research chemist for Eastman Kodak Co. (Rochester, N.Y.). “One is that the image quality of digital is better than that of analog. That’s not true.”
Dickerson illustrates what he means with the example of InSight, Kodak’s newest conventional film product. “You have wide differences in x-ray absorbencies, for instance in the area behind the mediastinum, the diaphragm and the heart. These materials absorb a great deal of x-rays, and as a result a film has to have enough sensitivity to image anything in those areas.” On the other hand, he says, “the lungs are essentially water- and air-filled, and are very radiotransparent. They have very high information content and very fine detail. And because such things as tumors are not very finely detailed, you want to image the chest with as low a noise as possible. A film has to have a very wide dynamic range to image all the anatomy in the chest. InSight does that. It’s an asymmetric film and it’s exposed using two asymmetric screens. It captures the same area of the body as if you were using two different films with perfect registration, but in one exposure.
“For neonatal imaging for preemies, InSight Pediatric has very low imaging noise. Noise obscures very fine information in a premature baby, particularly in the lungs. They’re very porous.” A disease called hyaline membrane disease, for instance, is patchy-looking on a radiograph. “Standard imaging noise obscures that. InSight features something called zero-crossover technology. It’s a layer coated between the emulsion and the support that prevents light crossover from the intensifying screens” that would cause a fuzzy image on the other side.
Another new film from Kodak, X-Sight, has what Dickerson calls “visually adaptive contrast. If a tumor was in a part of the body where the film was very dark, you wouldn’t be able to see it well. To overcome this deficiency of the eye, we increase the contrast of the film at the higher densities. You can see things equally well at low densities as at high densities. This improves the detection of lesions.” X-Sight G/RA and L/RA films produce high-contrast, wide-latitude radiographs that provide finer detail and 70 percent improvement in line-pair visibility over Kodak’s popular T-Mat films.
Dry film: Coming on strong
While PACS may not be pushing film aside in one broad stroke, there’s plenty of bumping and shoving over on film’s side. Large-format films are challenging CR and DR, dye is replacing silver, environmentally friendly processing is replacing pollution-causing methods and, perhaps most notably, dry technologies are overtaking wet ones. When the dust settles, the world of film imaging will be quite a different place than it once was.
“The statistics I see show that the usage of wet and dry films at this point is fairly equal, indicating a significant growth in the dry market,” says Jim McLain, senior manager for hard copy at Agfa HealthCare (Ridgefield Park, N.J.). Agfa’s line of dry film is called Drystar. Their biggest seller is the 3000 product, designed for radiology, CT, MRI, ultrasound, CR and DR.
“Most users of dry film are finding the image quality to be equal” to wet film, says McLain, “and the convenience factor is a major one, obviously. Dry pretty much eliminates all the environmental issues. You don’t have wet chemicals or processing, drains, or water supplies with dry media.”
Fuji’s new DryPix 7000 is a medical dry laser imager that delivers the performance and image quality of most wet laser imagers, making it ideal for high-throughput centralized imaging and replacement of wet laser imagers with throughput of 180 14″ x 17″ films per hour and 240 10″ x 14″ films per hour.
“Laser imaging is the area of the market that has been growing quite rapidly. As a subset, dry imaging has been growing at an extremely rapid rate,” says Robert Neary, national marketing manager for imaging systems at Fujifilm Medical Systems (Stamford, Conn.). “Dry laser film represents more than 50 percent of the film sold in the U.S. market. The double-emulsion conventional x-ray film market is shrinking at a similar rate to the growth of the dry imaging. The mammography film market represents about 5 percent. So we have put almost all of our resources into the development of dry imaging film technology. Fuji has developed technology that uses aqueous solvents instead of organic solvents,” which pollute. The latest of these is DI-HL. Neary says, “This film also has a very low base plus fog, a high dMax, and it enables very high-quality imaging. It has more rapid processing characteristics than our DI-AL film, which uses the same technology.”
DI-HL was introduced at RSNA last year, DI-AL in 1999; the current version of DI-AL is sixth-generation. Like all film vendors, Fuji constantly tweaks its existing products to improve them and keep up with hardware advances.
“The target is to come up with image quality from a dry imaging film that is equivalent to a conventional wet silver halite film,” says Neary. “Our DI-AL and DI-HL films have reached that point.”
Less silver, more stability
One of the new-and-improved technologies for x-ray film is direct thermal processing. Among other things, it makes images more stable. Fuji’s direct thermal film is called DI-AT. It is completely silverless and uses dye technology to make the images. Agfa’s direct thermal film is a Drystar product called 5500 DT2. It utilizes non-light-sensitive silver. Also, “It has an anti-curl layer built into the film,” says McLain, who calls that a “significantly helpful” technology never before available in Agfa dry media.
Direct thermal film development is accomplished by a single expose-and-process step using heat. No fixer is involved. McLain says that after the processing step with most other types of film, “any remaining silver stays in the film forever, and is still sensitive to light. The images can change.” He says independent studies show that media containing light-sensitive silver can continue to darken when exposed over time to light.
Another relatively new and decidedly helpful technology in many films is blue base. “Agfa has offered blue base since about 1995,” says McLain. “If you look at the U.S. market for all manufacturers, it is split approximately 75 percent blue, 25 percent clear. The choice is really one of personal preference, not diagnostic difference.”
Kodak’s Dickerson confirms there’s a scientific reason why more people choose blue-based film. “We found that by increasing the amount of blue tint in the support, we could enhance the perception of contrast. The reason is that the bluer support enhanced the scotopic vision. That’s the part of [retinal light reception] that involves the rods. Rods are responsible for seeing contrast. By increasing the amount of blue, you actually preferentially stimulate the rods. That improves the visualization of contrast. So in almost all our films now, we coat on a very high blue base.”
Leading advances
Of all the medical films available today, mammography media may have evolved the most. “In the last 15 years, there’ve been a lot of changes. Mammography images years ago were completely flat,” says Bill Cioffi, national marketing manager for women’s healthcare imaging systems at Fuji. Film manufacturers have since given film higher contrast to better pick out subtle abnormalities. “The greatest improvement came about six years ago when Kodak came out with the MIN-R 2000 system. It lowered the film speed and increased the screen speed,” thereby providing finer detail. Fuji’s answer was AD-M; the newest version, available later this year, provides higher contrast in the shoulder area of the film and an increased dMax (the density of black). The currently available mammography films have increased ability to register black that is some 10 percent better than that of previous generations. Fuji’s AD-M and Kodak’s MIN-R 2000, for instance, have a dMax of 4.0-plus.
Kodak’s Dickerson says, “In mammography, you have to have a film with very high contrast and narrow dynamic range. MIN-R 2000 has very narrow latitude. If you can’t see out to the skin line,” you may miss a calcification. MIN-RL dual-emulsion film, however, has that covered. “It uses a single intensifying screen,” says Dickerson. “One side of the film is high resolution and high contrast. The other side has a secondary emulsion with much wider latitude, so you essentially get two radiographs in one. One gives you high-contrast images of the mid-area of the breast, the other images up to the skin line.”
Agfa’s Drystar line also includes mammography film. It has a higher dMax than the other Drystar media. “Conventional radiology is looking for a dMax between 3.0 and 3.2,” explains McLain. “In the mammo field, the dMax is around 3.6. Drystar Mammo is speced at 3.5+ and has a wider contrast range” than conventional film.
An interesting side note about mammography films is how they’re driving yet another market — film digitizers. The new ultra-high-density mammography films have spurred digitizer manufacturers to soup up their products to keep up with optical density increases. The use of computer-aided detection (CAD) technologies is increasing, too, which bodes well for film vendors. Most of the FDA-approved CAD systems currently available are add-ons to analog mammography systems and produce more hard copy, at least for the time being.
Driver’s seat
Far from killing the film market, PACS is driving the medium to new strengths. “The healthcare market is now asking for digital imaging, which then drives the film,” says Bill Nicholas, product manager for hard copy imaging products at Fuji. “So the market isn’t looking for new film products; it’s looking for new dry film technologies.”
That said, what will happen in the battle between dry printing technologies and wet ones? “We’re already seeing that most wet laser imagers are starting to be replaced now,” says Fuji’s Neary. “You’re going to see a gradual decline in conventional double-emulsion wet x-ray film imaging as more and more people start to go digital and convert to PACS.” Bottom line: “Dry lasers will replace wet laser imagers almost completely within two years.”
Film is dead, long live film.
