Film processor QC: the German model.
During the past 10 years, Germany has developed a stringent set of quality standards for a number of aspects of radiology. The framework for developing these standards is the Deutsche Institut fur Normung. DIN is similar to the American National Standards Institute (ANSI), but DIN standards have more legal influence than the voluntary ANSI standards. DIN standards are not law, but they can be considered in the legal environment. For example, if a legal case is brought against a medical facility, the judge may ask whether the institution followed the DIN standard. If it did not, the institution would have to prove its own system was as good or better than the DIN standard.
A single DIN standard can be divided into many parts. For example, DIN 6868, which focuses on film processing, covers how testing equipment is manufactured, how medical facilities process radiographic film and how daily quality control is performed. As a result, the development of a DIN standard can involve experts from the government, industry, academia and professional practice.
Because of the traditionally strong role of the German federal government, DIN standards are recognized by all German states. In the United States, by contrast, the U.S. Food and Drug Administration controls the manufacture of medical equipment, but individual states oversee the daily use of that equipment. The U.S. approach results in a more varied implementation of standards than the German model, with the Mammography Quality Standards Act a notable exception.
DIN 6868, Part 55
The centerpiece of DIN 6868 is Part 55, "Image Quality Assurance in X-Ray Diagnosis," which covers test methods for "blue and ultraviolet-sensitive, as well as orthochromatic screen films, fluoroscopic films, duplicating films, films for photography from monitors and films for cineradiography" (DIN 6868, Part 55, February 1992). Other parts of the DIN 6868 standard cover all types of medical films and processing equipment.
In September 1987, the first draft version of DIN 6868 Part 55 went into effect. The final version will take effect later this year or in 1998. It requires large medical facilities to conduct sensitometric studies with the type of film that is most commonly used in the facility. Each film processor must be checked every day that it is used. For example, hospitals that use 20 film processors 5 days a week must perform 100 tests every week. In addition, separate sensitometric tests must be performed on mammographic film, significantly increasing the work load for facilities that perform mammograms.
The DIN requires radiology departments to collect key statistics, such as relative speed, average gradient, D-max, base + fog and temperature, and chart this information daily. Statistics must fall within the film manufacturer's published specifications. Equipment such as sensitometers and densitometers must have a tight range of repeatability and must provide information on long-term stability.
Medical physicists, government regulators and others who check the medical facility's QA/QC programs must use calibrated sensitometers that are recertified every 2 years by a licensed laboratory.
During the early stages of implementation of DIN 6868, equipment improvements were market-driven. Using traditional single-point reading densitometers and charting statistics by hand would have required additional personnel at most facilities. Anticipating this problem, in 1986 Peha Medicine Gerate GmbH of Sulzbach, Germany, introduced the first scanning densitometer, a device that could automatically read all 21 steps of a densitometric reading, calculate all necessary statistics and print a report. During the next several years, a number of other firms developed PC-based software to collect and analyze data. Today, these types of scanning densitometers and computer programs are manufactured by many companies and are commonly used throughout the world.
Subsequent revisions of DIN 6868 have set exacting specifications for equipment. In the first stage, members of the DIN committee, including representatives of the government, medical professions, film companies, processor equipment companies and testing equipment manufacturers, decided to develop a "master" sensitometer. The DIN members concluded that only the use of calibrated test equipment would permit an institution's film processing to be judged fairly. More importantly, calibrated equipment would be essential when trying to compare the processing of a type of film on two different machines.
Developing a master sensitometer has proven to be more difficult than expected, but manufacturers have produced "reference sensitometers" that are matched within 1% of an ideal reading and within 2% of each other. Using two of these reference sensitometers as quality control guides, manufacturers can produce calibrated sensitometers.
Densitometers also have stringent specifications. They have not, however, gone through the rigorous upgrading that sensitometers have. Densitometers should be provided with an independent means of density verification. With most densitometers, this is accomplished by using a calibrated filmstrip.
How the Talk Translates Into Action
Under DIN 6868, three parties are responsible for ensuring that radiographic films are processed correctly at a medical facility: the facility, the film manufacturer and the government. Perhaps the most unusual part of the German DIN system is that each film manufacturer must provide technical data about the expected performance of its film when it is processed under optimal conditions, including ranges of speed and contrast. The medical facility does not have to use the same chemicals or equipment as the film manufacturer, but its results must be within an acceptable tolerance.
Klaus Schwuchow, a member of the DIN 6868 committee and the president of Peha Medicine, recently told me that daily data collection, data evaluation and recordkeeping for processor quality control has become less burdensome with the implementation of automated densitometers and computerized programming. In addition, medical institutions indicate that the DIN requirements are not overly burdensome and that they have resulted in quality improvements in film processing.
Perhaps most important, the system encourages medical facility personnel and government representatives to work in unison. For example, when a medical facility introduces a new film, the DIN requires the film manufacturer to verify that the institution's processing chain produces results in tolerance with the film's published performance statistics. This quality check is verified by a government inspector, and only then is the medical facility permitted to begin using the new film.
Although this may seem like overregulation, everyone benefits. The film companies educate medical facilities to produce films that match the quality their films are designed to produce. The medical facilities know that their equipment is working at optimal levels, so they produce images of higher quality. The German government, as the watchdog for the medical consumer, gains an added level of confidence that its citizens are being better served.
What Is the Price of Quality?
When I first learned about DIN 6868, I assumed that the cost of ensuring such a high level of quality would be substantial. I have seen no studies that indicate whether my assumption is true or false. However, with a population of 80 million, a strong medical infrastructure and the innovative products to counteract potentially higher labor costs associated with the DIN standards, it appears certain that the competitive German market forces eventually will drive down the cost of implementation.
Although it is true that "quality always has a higher price," it also is true that in today's worldwide economy, market forces can make quality more affordable.
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|Title Annotation:||quality control|
|Author:||Giesberg, Daniel J.|
|Date:||Jul 1, 1997|
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