This is the conclusion of a two-part white paper on the essential physics of building or modifying a diagnostic radiology facility, contributed by W. Geoffrey West of West Physics Consulting.
Step 5: Shielding design
Coincident with equipment registration or radioactive materials (RAM) licensing, the facility planner will need to contract a physicist to design the lead shielding that will be installed in the walls, doors, and windows to provide radiation protection for the staff, patients, and visitors. This design process is actually better described as analysis and specification: the physicist will review the facility plans, drawings, and blueprints, and perform calculations to determine what thickness of lead sheet (or other shielding materials) will be required in each barrier. Typically, the physicist will not need to visit the site to perform this step -- it may all be done remotely.
The physicist's goal is to shield the facility in such a way that the radiation dose to all facility workers, patients, and visitors stays well below applicable federal dose limits. The current U.S. standard in use for this analysis at the present time is called NCRP-147, which recently replaced NCRP-49, a standard which had been in use for almost three decades.
When considering a physicist for this type of work, the facility planner would be wise to gauge the individual's familiarity and experience with shielding designs under this new standard as it is significantly different and more complex than the prior guidance. Utilization of a board-certified medical or health physicist (look for board certification by the American Board of Medical Physics, American Board of Health Physics, or American Board of Radiology) is strongly advised for this particular activity due to its importance, technical nature, and liability issues. Also, many states require that physicists be registered for this type of activity in their state, so the facility planner may also wish to ask potential physicists about this credentialing.
During the shielding design process, physicists will not only require the facility room dimensions and equipment types and locations, but will also need to know the function of surrounding spaces (office area, waiting room, parking lot, etc). As radiation operates in three dimensions, qualified physicists will inquire about the function of spaces above and below x-ray rooms or nuclear medicine areas, as floors and ceilings may also require shielding. To the extent possible, diagnostic physicists will attempt to anticipate facility's postproject patient throughput, but in the absence of this information, will rely on industry averages at their disposal.
Once the physicist has specified the shielding requirements, the architect and general contractor are then legally responsible for following these shielding specifications in the design and construction of the space.
It is frequently valuable during the shielding design process to place the physicist in direct contact with the facility architect or general contractor. This can, in many cases, expedite the process and allow for the physicist's feedback to those parties should they identify any design problems vis-à-vis radiation safety. The physicist can also provide valuable construction tips to avoid common mistakes in the installation of lead shielding -- mistakes that could necessitate costly rework in some cases.
Due to the mathematical complexity of this process and its obvious potential liability implications, a good medical physicist will want enough time to perform this process methodically and check for errors. Thus, the facility planner should allow one to four weeks for the shielding design process, depending on the size and scope of the operation and layout.
Step 6: Shielding integrity survey
NCRP-147 specifies that all diagnostic shielding installations should be inspected for integrity (i.e., that the shielding was installed per the specification without voids or defects) postconstruction. In addition, many states require that proof of this inspection be sent to them or kept on file at the facility in the event of future inspection.
There are numerous methods of completing shielding integrity surveys, all of which a competent diagnostic medical physicist can explain and perform. Some of these methods are performed after construction is essentially complete and all x-ray or nuclear medicine equipment has been installed.
Other methods can be performed prior to the finishing of walls so as to allow for easier (and cheaper) corrections should the need arise. The facility planner should discuss these options with the physicist during the shielding design phase (step 5, above) and plan for the survey at that time. In all cases, physicists (or their staff) will need to personally visit the facility to complete this survey; the process normally takes roughly 30 minutes per room.
Step 7: Equipment acceptance testing
Immediately after installing a new piece of diagnostic imaging equipment, and (preferably) prior to its first clinical use, an acceptance test should be performed on the equipment by a medical physicist. This test is an extremely thorough survey of the equipment and its capabilities, designed to confirm that the device was installed and set up properly and that it meets all vendor and industry performance specifications.
Although some facilities choose to rely on the goodwill of the vendor or installer to certify the proper performance of its equipment, not having an independent and disinterested check on the performance of highly complex and expensive machinery by a qualified professional is unwise.
Additionally, the cost of such a test is typically fractions of a percent of the purchase price of the equipment in question, thus constituting a very prudent insurance policy against future operational problems. By way of analogy, having an acceptance test on newly installed equipment is akin to employing an independent home inspector during the purchase of a home. Finally, it is worth pointing out that many states require this type of test on newly installed diagnostic imaging equipment for health and safety reasons.
Many diagnostic imaging facilities negotiate the acceptance test into the actual sale of the machinery or withhold final payment on the device until such time as any performance concerns on the part of the physicist have been properly resolved. From a business perspective, this arrangement clearly provides an added incentive for the vendor or third-party installer to execute a meticulous and successful installation. For the facility planner, it is important to arrange for the acceptance testing as far ahead of the installation date as possible and to keep the contracted physicist informed of any schedule changes or other events that may affect the testing.
Step 8: Poststart-up equipment testing and consulting
Once operational, the facility will have periodic ongoing medical physics needs. For example, during the early phase of operation, the facility may wish to pursue American College of Radiology (ACR) or Joint Commission on Accreditation of Healthcare Organizations (JCAHO) accreditation of one or more modalities for various regulatory or business reasons.
In some states, ACR accreditation has become mandatory for full reimbursement in a number of modalities. In addition, many insurance carriers now require it for reimbursement. The medical physicist will assist in this process, both in terms of providing the required physics testing for the accreditation application, and in helping facility personnel navigate the administrative process. It is therefore important that facility management retain a physicist experienced with a particular modality's accreditation process, preferably one with a proven track record accrediting the particular equipment make and model in question.
Whether the newly installed equipment is ACR-accredited or not, in most cases, an annual physics test will be required on x-ray producing equipment by the applicable state regulatory authorities (or by the U.S. Food and Drug Administration in the case of mammography). Because the particular testing requirements vary considerably from state to state, it is highly advisable to consult the relevant agencies before facility start-up to ensure that the requirements are clear.
In some cases, state inspectors will perform the annual testing, but in most cases private consulting physicists are used. These consultants will generally be familiar with the particular requirements of the states in which they operate and can assist the site management in meeting those requirements. In the case of MRI, annual physics testing is required for facility accreditation by the ACR, but is not required by states at this time. However, many nonaccredited MRI facilities choose to have the annual testing done anyway because of the resultant image quality improvements, refresher training opportunities, and other advantages to the facility.
Conclusions
Building or modifying a diagnostic imaging facility successfully is a challenging and complex process that involves the participation of a multitude of professionals. This white paper described the particular set of responsibilities of one individual in that process -- the medical physicist.
By understanding the general steps that a physicist must take throughout this process, how long these steps take, and when each step must occur, the facility planner can better coordinate the physicist's activities with other parties in the process: architect, contractor, site management, equipment vendor, installers, service personnel, and applications support personnel.
By W. Geoffrey West
AuntMinnie.com contributing writer
July 6, 2006
W. Geoffrey West is president of West Physics Consulting, a Smyrna, GA-based diagnostic medical and health physics consulting and testing company. The firm currently handles more than 100 clients in 27 states and specializes in complex problems and modalities. For more information, West Physics Consulting can be contacted at 866- 275-9378 or via its Web site.
Related Reading
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Pediatric MRI and suite templates: If the shoe doesn't fit, don't wear it, April 25, 2006
MRI vendor suite templates: What they don't show, December 8, 2005
Copyright © 2006 West Physics Consulting
