Archival storage characteristics of 3M™ DryView™ Laser Imaging Film from Imation™

DryView Laser Imaging Systems use a dry photothermographic imaging process to develop diagnostic-quality medical imaging films. This innovative technology eliminates many of the costs, inconveniences and environmental impact associated with traditional processes that require “wet chemistry.”

DryView Laser Imaging Film-which looks and feels like traditional “ wet processed” film-is specially designed for these new laser imaging systems.

The archivability of DryView Laser Imaging Film was a key consideration in the development of this new technology, because health care facilities often must store medical imaging films for as long as 30 years.

Arrhenius testing conducted by our laboratories indicates that DryView Laser Imaging Film exceeds even the most demanding archivability requirements. In fact, the data show that when stored at the ANSI recommended temperature of 77^oF (25.0^oC), the film can be archived for hundreds of years.

How DryView Laser Imaging Film responds to Arrhenius Testing

“Arrhenius testing” is the widely accepted method for measuring the archivability of photographic materials. This method is cited in a number of ANSI and ISO standards, including ANSI PH1.66 (“ Specifications for Stability of Radiographic Films”), ANSI 1T9.19 (“Specifications for Stability of Thermally Process Silver Microfilm”), and ANSI 1T9.9 (“Method for Measuring Stability of Color Photographic Materials”).

Arrhenius testing is also frequently referenced as evidence of long-term image permanence in literature published by major photographic manufacturers.

The Arrhenius test is based on work done by Swente Arrhenius in the 1890s. He discovered the rate of many chemical changes is proportional to the temperature at which they occur. This relationship allows scientists to predict changes at room temperature by measuring those same changes at higher temperatures (where changes occur more rapidly).

To date, more than 40 incubation studies at five different temperatures have been completed on DryView Laser Imaging Film. Data from these studies have allowed Imation to predict with a high level of confidence that developed DryView Laser Imaging Films, when stored at reasonable temperatures, will retain diagnostic information far longer than required by the medical profession.

Test procedure:
There are two common methods for incubating samples during Arrhenius testing. The traditional method involves packaging material in foil envelopes to maintain consistent moisture content throughout incubation. With this method, only the temperature of the incubating enclosure is critical. Another technique, known as “free-hanging,” involves placing samples in the incubation chamber so the entire surface of the sample has air exposure. The sealed envelope method was chosen for our test, since it more closely resembles how medical films are stored. This method has also been shown to provide more conservative predictions.

Sample preparation:
Sample strips of DryView Laser Imaging Film were exposed and processed to give a continuous gray scale image from Dmin, to an optical density of 3.1. The films were then measured on a computerized densitometer which was capable of determining optical density at 0.25 cm intervals along the strip. Finally, the samples were allowed to equilibrate for at least 15 hours in a 70^oF (21.1^oC) 50% RH room, after which they were individually double-packaged and sealed inside foil pouches.

Incubation:
Incubation ovens were maintained at temperatures of 113^oF, 122^oF, 131^oF, 140^oF and 149^oF or 45^oC, 50^oC, 55^oC, 60^oC, 65^oC. Ten sealed envelopes of each new test material were placed in each oven at the beginning of the study. Individual envelopes were removed from the ovens at predetermined intervals, allowed to equilibrate to room temperature, then re-measured on the computerized densitometer. Density changes between pre-incubation and post-incubation were then calculated for each strip.

Analysis:
The study generated delta densities for each point along the continuous gray scale at 10 time intervals for each of the five incubation temperatures. The location of the maximum change along the gray scale image was determined for each film. The density change at this point was then plotted in relation to incubation time to determine time-to-failure. Once time-to-failure was determined for each incubation temperature, the reciprocal temperature (in kelvins) was plotted against the logarithm of the time-to-failure. The results are summarized in the preceding chart.

Conclusion:
Extensive Arrhenius testing, with its accepted predictive procedures and conservative assumptions, indicates that DryView Laser Imaging Film has excellent archival storage stability which consistently meets or exceeds the requirements for diagnostic medical imaging.

For more information

Contact your local Imation sales representative, or call Imation at 1-888-466-3456, ext.4-6000. Or call our Customer Resource Center directly at 1-800-328-2910.

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