Answer to Question #3668 Submitted to "Ask the Experts"

What should a health physics auditor look at when inspecting a medical clinic with only a diagnostic x-ray machine?

Assuming that you are referring to a standard radiographic x-ray unit, that is, ceiling-mounted overhead unit for x-ray imaging of extremities, head, chest, etc., and not a fluoroscopy unit, a wide range of items can be reviewed during an audit.

At the very least, the auditor should refer to the state regulations that cover the use of this type of equipment where it is located. An audit at this level would probably include testing the unit for various technical parameters, such as kVp and timer accuracy, mAs linearity, exposure reproducibility, beam output, beam quality, light field/x ray/image alignment, etc. Also, the auditor should observe any other requirements that may exist, such as warning signs/lights, warning label on control panel, audio/visual indication of x-ray production, technique factors visible from operator's console, dead-man switch, etc. Scatter radiation should be measured to verify that radiation doses to the operator and members of the public are within acceptable limits. For a new installation, shielding recommendations are usually made and a survey is performed to verify the integrity of the installed shielding.

Since states typically register or license x-ray machines, an auditor should verify that the machine is properly registered and a copy of the registration is available. In addition, the facility is probably required to have dosimetry or proof that dosimetry is not needed. When dosimetry is present, records should be reviewed to determine if personnel with dosimeters are not exceeding dose limits and are using dosimeters properly. A review of the facility’s training program may also be needed to verify that all personnel who access the x-ray room have received training corresponding to the risk they are subjected to.

Some states have quality-assurance programs that require additional items to be in place such as quality-control tests for film processors, dark room fog testing, film/screen contact testing, lead apron integrity checks, repeat/reject analysis, etc. A review of image quality may also be needed. Usually the quality-control tests are performed by an x-ray technologist and are reviewed by a physicist.

In summary, the x-ray machine auditor should review the applicable rules for the state in which the x-ray unit is located to determine the minimum amount of effort needed to perform an adequate audit. A comprehensive review can be found in National Council on Radiation Protection and Measurements (NCRP) Report No. 99 (1998). The auditor should work with the facility to determine the extent of an audit, helping to make sure the facility is producing quality images, using the ALARA principle, and keeping within state regulations, all while trying not to duplicate someone else’s effort. States also vary widely on who performs inspections of x-ray equipment. Some states do their own inspections whether or not a physicist has evaluated the equipment and/or the program, while other states license or certify physicists to perform the inspections for them. In these cases, there may be state-provided forms that the auditor must complete and submit on behalf of the facility. It may also be necessary to enlist the assistance of a medical physicist regarding image quality issues. Auditors must determine for themselves if the work is within their scope of practice.

Ken "Duke" Lovins, CHP

Reference
National Council on Radiation Protection and Measurements. Quality assurance for diagnostic imaging equipment. Bethesda, MD: NCRP; NCRP Report No 99; 1998. Available at: http://www.ncrppublications.org

Editor’s Note: Individual state radiological programs can be found at the Conference of Radiation Control Program Directors Web site.