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The IHS diagnostic X-ray equipment radiation protection program.

The Indian Health Service (IHS) operates or contracts with Tribal groups to operate 50 hospitals and approximately 165 primary ambulatory care centers. These facilities contain approximately 275 medical and 800 dental diagnostic x-ray machines. IHS environmental health personnel in collaboration with the Food and Drug Administration's FDA) Center for Devices and Radiological Health (CDRH) developed a diagnostic x-ray protection program, including standard survey procedures and menu-driven calculations software. Important features of the program include the evaluation of equipment performance, collection of average patient entrance skin exposure (ESE) measurements for selected procedures, and quality assurance. The ESE data, collected using the National Evaluation of X-ray Trends (NEXT) protocol, will be presented. The IHS Diagnostic X-ray Radiation Protection Program is dynamic and is adapting to changes in technology and workload

History

The IHS Diagnostic X-ray Radiation Protection Program has undergone many changes since the agency was created in 1955. The IHS Office of Environmental Health and Engineering was assigned major responsibilities for program management, especially equipment performance evaluation and personnel dosimetry monitoring. Prior to 1978, most IHS area programs were ill-prepared to implement a comprehensive radiation protection program due to inadequate staff training and survey equipment.

A major change occurred when the FDA initiated compliance regulations for implementation of The Radiation Control for Health and Safety Act of 1968[1]. This act empowered the FDA to evaluate x-ray machine performance. Towards this end, courses were developed in the late 1970s to train state and IHS surveyors to do the equipment evaluations.

The CDRH, formerly the Bureau of Radiological Health, also developed a standard test method with accurate test equipment. One important device was a test stand made of Lucite[R] with several components. The CDRH Test Stand allowed surveys to be performed with a standard geometry allowing consistent calculations of results. This was a major breakthrough because diagnostic x-ray equipment could be evaluated consistently across the country. Using the same protocol on machines of like components allowed for comparisons between machines that could be used for recalls, trends analysis, etc.

The test stand shown in Figure I consists of two upright sides with a slotted top and bottom. The uprights contain slots for mounting the slide assembly at differing heights. The slide assembly has a grid of radiopaque material mounted on it to facilitate measurements of the x-ray and light fields. One side also contains two holes for mounting the ion chamber in the x-ray beam. The focal spot assembly consists of a plastic plate with two metal strips on a film, and the known distances between the image and object allows for calculation of location of the focal spot. In addition, several sheets of aluminum of varying thickness, sheets of copper and lead, and a light meter are part of the total kit.

The radiation meter currently used was developed to CDRH specifications and has an exposure range of 0.02 mR to 99.9 R. The battery operated meter can operate in several measuring modes: pulse exposure (mR), pulse duration (milliseconds), exposure MR), and exposure rate (mR/min). The instrument uses an ionization chamber to measure the exposure incident on the sensor; the voltage in the ionization chamber is measured by the circuitry, and the appropriate measurement is displayed on a digital readout.

While the FDA'S Compliance Testing program is important, there were limitations. The standard test protocol only evaluated a limited number of test parameters, the raw data had to be analyzed by a main frame computer in FDA headquarters, and operator quality assurance performance was not addressed. The problem of delayed feedback was solved in 1984 by one of the authors when he developed a PC-based x-ray calculations program written in a compiled Basic programming language. The ability to assess machine performance data quickly was important in correcting hazardous conditions.

In 1984, the CDRH developed the Radiation Survey Procedures - Use Control survey manual[2] to evaluate quality assurance procedures. They also began development of a draft Federal Facility Survey Procedures Manual to provide a more comprehensive method of evaluating x-ray machine performance; however, it remained unfinished.

The IHS and the CDRH began a joint project in 1989 to develop a comprehensive x-ray survey procedure. This comprehensive approach would combine some features of the original compliance test with the draft Federal Facility Survey method. In addition, it would include all of the components of the use control manual. The new project required the development of survey forms, a new computer calculations program, and a complete instruction manual.

The computer software is written in Clippers[R], a database compiler, and is menu-driven. Test protocols developed to date include general purpose above table radiographic, mobile radiographic, and dental radiographic units. Copies of the forms, software, and manual have been distributed to FDA auditors and state surveyors.

One menu option for entrance skin exposure (ESE) allows the x-ray surveyor to analyze patient radiation exposure from typical diagnostic procedures. This test requires the use of a phantom, a device that is used to simulate a human body part as it would appear to an x-ray machine. Phantoms have been created from actual body parts, such as jaw section for use with a dental x-ray machine. Other times a gallon jug of water has been used to simulate soft tissue. The ideal phantom would appear as dense to an x-ray beam as the corresponding body part it represents; that is, the same percentage of incident photons should be transmitted through the phantom as would be through the true body part. In addition, it should scatter radiation similarly as the original body part would.

Examples of phantoms developed by CDRH to provide standard information on ESE include: Posterior (P)/Anterior (A) Chest, Lumbar-sacral Spine, and A/P Abdomen projections as shown in Figures 2 and 3.

These phantoms are blocks of Lucite[R] or Lucite[R] and aluminum that are used in conjunction with die radiation meter. Although they do not physically resemble a chest or abdomen, there is a strong correlation between the image of the phantom and the quality of the image of a true body section on an x-ray film for a given machine setting. The machine is set to the technique factors used by the facility for the projection being tested. A radiograph is made of the phantom and the exposure is noted. When the film is developed, the image of the phantom should be uniform and have an optical density of approximately 1.0-1.6 optical density units. This range of density should give a usable radiograph of a patient of the same body thickness. If the test film is not within this optical density range, the problem could lie with the processor rather than the x-ray machine or techniques used. The use of phantoms allows for comparison of the patient exposure of a machine to published national average data. If the machine is higher than the national average, adjustments should be made to lower patient exposures.

IHS/CDRH Training Program

Prior to 1980, there were no formal mechanisms to train IHS environmental health personnel in radiation protection survey methods. The FDA provided a one week compliance test course for IHS personnel during the years 1981 through 1987. This training emphasized survey techniques but not the concepts and rationale. It became apparent that as the test equipment and procedures became more complex, more intensive surveyor training would be necessary. This fostered an interagency agreement (IAG) between the IHS and the CDRH. The IAG allowed the IHS to reimburse the FDA for equipment purchase, calibration, and surveyor training.

The x-ray surveyor training program consists of three week-long courses. Part one emphasizes basic physics and biological effects. Part two is a techniques course. This course teaches equipment evaluation methods and is similar in approach to the old compliance course. Part three emphasizes quality assurance, especially methods to improve imaging and to reduce patient exposure.

The final phase of the training program consists of a field evaluation by an FDA radiological health representative. Candidates or evaluation are expected to have completed sufficient numbers of diagnostic x-ray facility surveys as a prerequisite. Surveyors are expected to demonstrate knowledge of test procedures and associated standards, proper interviewing techniques, and the ability to communicate survey findings in a comprehensive report. The FDA representative observes each candidate in a one-on-one situation and prepares a written critique. The critique and the surveyor's report of findings are then forwarded to headquarters to be reviewed by a panel of IHS and FDA specialists. Certificates of competence are issued to successful candidates. As of May 1992, seven of ten individuals passed the certification process. Individuals who fail to pass the first time are given the opportunity to gain additional experience and be retested. The goal of the program is to have at least one certified individual in each of 12 IHS areas. Some of the large programs such as the Navajo nation will require three certified surveyors.

The training and certification process is an important means of providing a quality radiation protection program. It is also important in meeting a standard of the Joint Commission on Accreditation of Healthcare Organization (JCAHO). The JCAHO requires that each accredited hospital or clinic identify who is qualified to evaluate radiation protection practices at the facility [3]. The above training and certification process serves this purpose.

Overview of Survey Findings

The initial focus of the IHS radiation protection program was to identify problems with the x-ray machine itself Table I lists the main parameters surveyed under the present regulations for general purpose type x-ray machines. The specific methods for calculation and test protocols can be found in the IHS Radiation Protection Manual[4].

In some locations of the Indian reservations, there are serious problems with incoming line voltage fluctuation, difficulty in obtaining fully qualified operators of x-ray equipment and qualified biomedical engineering technicians. These factors can have a severe impact on machine performance. While problems have been identified in the past, significant improvements have been made. Attempts are being made to attract qualified machine operators, areas are recognizing the value of a comprehensive biomedical engineering program, and outmoded equipment is being replaced.

The new area of focus is quality assurance. Production of quality radiographs requires properly functioning x-ray machines, proper darkroom design and procedures, optimal technique factors, patient positioning, and the correct film and intensifying screen combinations[5]. IHS x-ray surveyors have identified proper maintenance and operation of the automatic film processor as one of the key factors in assuring a quality radiograph. The CDRH developed a series of test protocols to assist the surveyor in evaluating processor performance[2]. One of the most useful is called die Sensitometric Test for the Evaluation of Processing (STEP). This standardized test allows all processors to be graded in a consistent manner. A range of scores from 80 to 120 is considered acceptable. A score of 80 or less means that the patient must receive 20% or more radiation to obtain an optimal film. Scores above 100% mean less radiation is required to achieve the same quality radiograph; however, process speeds that are too high (i.e., above 120) may result in a degraded image on the film.

One very important aspect of radiation protection is the reduction of patient radiation exposure from typical diagnostic x-ray procedures[6]. The FDA has been compiling radiation exposure information for over 20 years in programs called the Nation Wide Evaluation of X-ray Trends (NEXT). The IHS began compiling its own data in 1989. Table 2 represents the "old" 1978 NEXT study, the "new" 1987 NEXT study, and compiled IHS data for several areas from 1989 to December 1991.
Table 2. A Comparison of "Old" NEXT, "New" NEXT, and Complied
IHS Data.(1)

Examination 1978 1987 (7) IHS

Chest 30 15 15.3
Lateral Skull 300 _____ 105
Abdomen 750 300 257
Lumbar Sacral Spine 1000 350 275
Wrist n/a n/a 5.9

Values are reported in milliroentgens (mR).


The IHS data are still very preliminary, but initial results compare favorably with national averages. Some words of caution in interpreting these results are in order. First, new faster radiographic film systems have had a major impact in reducing exposure. Second, while the amount of radiation exposure is important, it is the film quality that is most important. If radiation exposure is reduced to the point where the film loses diagnostic information, the radiograph must be repeated.

IHS Radiation Protection Work Group

A work group was formed in 1990 to ensure that the IHS maintains a proper focus in addressing radiation protection priorities. The group is composed of three environmental health specialists, a radio- logical technologist, and a biomedical engineering technician. The group's first project was the revision of the IHS Radiation Protection Policy. This process was cumbersome, taking the better part of a year to complete, but it ensured an opportunity for policy development by all affected parties. Other tasks for the group include the development of a new quality assurance survey system and a fluoroscopy survey procedure. Both documents will require the development of computer software and extensive field testing.

The process of developing policy and programs is painfully slow, but the final product will be of direct benefit to the IHS and other radiation protection programs.

Discussion

The IHS diagnostic x-ray radiation protection program evolved over the past 15 years from its infancy to one of the nation's leaders. This success can be traced to the benefits derived from the cooperative efforts of the CDRH and IHS. This cooperation allowed the modification of survey protocols and training procedures, resulting in a practical, comprehensive system. This system will in turn benefit the U.S. healthcare system, in that improvements in x-ray equipment performance and radiological quality assurance will reduce the number of repeated radiographs and reduce patient radiation exposure.

References

[1.]Regulations for the Administration and Enforcement of the Radiation Control for Health and Safety Act of 1968, DHHS Pub. FDA 88-8035. CDRH, FDA, USPHS, DHHS. Section 1020.31, 45-58. [2.]Radiation Survey Procedures - Use Control, Field Manual CDRH, FDA, USPHS, DHHS. [3.]The Joint Commission on Accred. of Healthcare Org. (1993), "Diagnostic Radiology Service" Hospital Accreditation Manual. [4.]Diagnostic X-ray Radiation Protection Survey Procedures Manual. IHS, USPHS, DHHS. [5.]NCRP Report No. 99 (1988), Quality Assurance for Diagnostic Equipment, The Natl. Council on Radiation Prot. and Meas.,Inc. (NCRP), Bethesda, MD, 2-3. [6.]Public Law 97-35, Consumer-Protection Radiation Health and Safety Act of ]981, (42 USC 10001, Subtitle 1). [7.]Average Patient Exposure Guides (1992), Pub. 92-4, Com. on Quality Assurance in Diagnostic Radiology, Conference of Radiation Control Program Directors, Inc., 3.
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Title Annotation:Indian Health Service
Author:Suleiman, Orhan
Publication:Journal of Environmental Health
Date:May 1, 1994
Words:2433
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