C-arms and mini C-arms have become standard equipment in many outpatient surgery facilities, where they're used for orthopedic, pain management, urological and many other types of procedures. Well-connected facilities might have access to a staff of radiology experts to help maintain C-arms, provide safety training and often perform all of the fluoroscopy procedures. Independent facilities, however, might be left on their own to determine their compliance with radiation safety and operator-training requirements, which vary from state to state.
The primary beam exits the X-ray tube and passes through the patient. Some of the radiation is absorbed by the patient, some is transmitted to the image intensifier and some is emitted as scatter radiation, which is the primary source of radiation exposure for personnel. About 5 percent to 15 percent of the beam reaches the image intensifier, where it is converted into the image. The C-arm's kVp (peak kilovolts) determines the penetration of the beam, which affects image contrast and radiation dose. The C-arm's mA (milliamperes) determines the number of X-rays, which affects radiation dose and image noise.
The lack of universal guidance on these issues might cause many facilities to become lax in their C-arm safety procedures, says G. Donald Frey, PhD, a medical physicist at the Medical University of South Carolina in Charleston. "You can't smell, taste or immediately feel radiation, so people tend to get casual about it," he says. Personnel sometimes stop wearing lead aprons because they're uncomfortable to wear. Perhaps they neglect to get their C-arms serviced properly. Or they employ untrained operators who use high doses of radiation to achieve the best image quality, when, as Dr. Frey says, "the goal of fluoroscopy is not to shoot the best image possible, but to get the best balance between image quality and radiation dose."
We asked a number of experts for their best tips on C-arm safety. Here's what they recommend.
1 Check your state's requirements.
State requirements for C-arm monitoring and operator credentialing vary. California, for example, requires weekly monitoring of fluoroscopy tube current (mA) and kilovolt potential (kVp) on C-arm units that are equipped with automatic brightness control. Maryland will begin requiring all C-arm operators to have at least four hours of radiation safety training starting next month.
Mahadevappa Mahesh, PhD, a medical physicist at Johns Hopkins University School of Medicine in Baltimore, says he's seen cases where facility management didn't get the proper safety guidance when they first started fluoroscopy, prompting concerned personnel to call OSHA. "This tends to trigger a whole lot of regulatory alerts," says Dr. Mahesh. Much better, he says, to know your state's requirements before the first C-arm is delivered. Dr. Mahesh suggests calling your state's Department of Health or Department of Environmental Services; some states might have a Department of Radiation Safety that can help make sure your facility is compliant. Alternatively, you could call a neighboring hospital that performs fluoroscopy or a professional organization such as American College of Radiology (www.acr.org), the American Association of Physicists in Medicine (www.aapm.org), the American College of Medical Physics (www.acmp.com) or the Health Physics Society (www.hps.org).
2 Call on the expertise of a medical physicist.
Medical physicists can ensure that your C-arm setup is safe, advise you on monitoring and radiation safety training issues, and suggest ways that you can fine-tune your system to ensure optimal image quality. "The physicist adds perspective to the overall process of fluoroscopy, taking both image quality and safe operation into account," says Dr. Frey.
Ask your department of health or a local hospital to recommend a qualified medical physicist who is certified by the American Board of Radiology or the American Board of Medical Physics. You could also contact the previously mentioned professional organizations for guidance.
3 Make sure your C-arm operators are properly trained.
There's no universal credentialing standard for C-arm operation; in many states, physicians operate C-arms and mini C-arms with little or no safety training. Fortunately, more and more medical groups are becoming aware of the need for radiation safety training; the American College of Cardiology and the American Heart Association, for example, now strongly recommend it.
At some facilities, such as the Indiana Surgery Center North in Indianapolis, only qualified radiation technologists perform fluoroscopy procedures, says executive director Shannon Meier. Physicians may operate C-arms at the Oak Park Surgery Center in Arroyo Grande, Calif., but only if they've received fluoroscopy and radiation safety training, says director Lisa Evans.
The level of training an operator needs depends on the intensity and the duration of the procedures, says Dr. Frey. Training courses should include instruction on C-arm operation and at least the basics of radiation physics, radiobiology and radiation safety.
Not only do trained personnel know how to get the best images, but they use less fluoroscopy time as well, which results in less patient and staff exposure to unnecessary radiation, says Dr. Frey. Your medical physicist or one of the national radiology organizations can advise you on C-arm operator training and radiation safety training for your physicians and staff.
The Effects Of Radiation
Radiation can have two types of effects on humans: stochastic and nonstochastic, says Mahadevappa Mahesh, PhD, a medical physicist at Johns Hopkins University School of Medicine in Baltimore.
4 Wear proper protection.
C-arm safety apparel usually consists of an apron of at least 0.5mm lead equivalence, which attenuates scattered radiation beams by a factor of 20, according to the American Association of Physicists in Medicine. Aprons used to be heavy and difficult to wear, but now, many manufacturers offer lightweight, more comfortable lead composite varieties that provide just as much protection as their heavier counterparts, says Dr. Mahesh (Dr. Frey notes that some states require 0.5mm aprons, so check your local regulations). At the Ohio State University Medical Center in Columbus, director of perioperative services Lynda Petty is gradually switching to lightweight 0.35mm thickness aprons; Ms. Petty also stocks different sizes so everyone can be assured of a good fit.
Maintain your aprons carefully. Test them every six months by simply imaging them with the C-arm and examining the image for cracks or imperfections, says Dr. Mahesh. "In the absence of any standard to quantify the extent of damages, the experienced operator can determine whether the apron should be reused or discarded," he says. He adds that it's important to keep a log of apron examinations, as they're often requested during JCAHO inspections.
Personnel who work within a three-foot radius of a full-sized C-arm may want to wear extra protection, such as thyroid collars and wraparound glasses, suggests Areg Bejanian, PhD, a California-based medical physicist.
Don't let protective apparel give you a false sense of security, warns Dr. Mahesh. He's seen instances where fluoroscopy operators don lead-lined gloves, which can be as thin as latex gloves, believing that they provide complete protection, and then repeatedly place their hands in or near the primary beam, causing stray radiation to scatter off the fingers. Experts agree that no matter how well you're protected, it's best to stay as far from the X-ray tube as possible. Also, never place you hands in the primary beam, and turn the beam off before manipulating patients.
5 Monitor radiation exposure.
In most cases, radiation monitoring badges, or dosimeters, are worn outside the apron at the collar level. State requirements for dosimeter usage vary - in South Carolina, for example, anyone who enters the room where a C-arm is being used needs to wear one, says Dr. Frey. Experts agree that pregnant staff should wear one badge at collar level and another below the apron on the abdomen.
You should test dosimeters once a month, or as often as the manufacturer or testing company recommends. Depending upon your C-arm usage, you might be able to relax monitoring requirements, says Ms. Meier. With the help of her medical physicist, her facility ran a study of dosimeter badges and determined that the level of radiation was too low to require consistent monitoring. She points out, however, that pregnant personnel always wear aprons and radiation badges. Experts recommend always starting out with regular monitoring; don't discontinue it without an expert's approval.
6 Pay attention to C-arm, patient and staff positioning.
The major source of radiation scatter is the patient. To minimize the patient entrance dose, experts recommend positioning the X-ray tube as far from the patient as possible. To absorb the scatter, they recommend moving the image intensifier as close to the patient as possible; this will also minimize patient skin exposure and help create sharper images. According to the American Association of Physicists in Medicine, personnel standing three feet from the patient receive 1/1000 of the patient's exposure if they take no protective measures. Taking one step back from the table can cut exposure radiation rate by a factor of four; using a lead shield cuts the dose by a factor of 10.
Position the X-ray tube under the patient, if possible. During lateral or oblique fluoroscopy, the AAPM recommends that personnel stand on the side of the patient furthest from the X-ray tube and closest to the image intensifier.
Radiation Dose Limits
The National Council on Radiation Protection and Measurement suggests an upper limit of 5 rems per year for the entire body (Note: the traditional unit of radiation exposure is the Roentgen; rem stands for Roentgen Equivalent in Man). The lens of the eye should receive no more than 15 rems per year, and the skin, individual organs and extremities should receive no more than 50 rems per year. Pregnant personnel should not receive more than 50 millirems during any month of their pregnancy. Radiation experts agree that lower exposures result in a lower likelihood of short-range and long-range effects, so they recommend that any radiation safety program be built around the core principle of ALARA, or keeping radiation exposures As Low As Reasonably Achievable.
7 Don't get lax around mini C-arms.
"Mini C-arm safety tends to fall through the cracks," notes Dr. Mahesh. "Mini C-arms do output less radiation than full-sized units, but operators still need to use caution around them."
If mini C-arms are used for more than 10 minutes, the amount of scatter radiation is quantifiable. So it's important that you take precautions, such as wearing aprons and dosimeters, unless, as was the case at the Indiana Surgery Center North, your radiation safety expert advises otherwise. "Our medical physicist determined that the level of radiation around our mini C-arms was so low that aprons and dosimeters weren't necessary," says Ms. Meier. "Therefore, we leave the decision to wear them up to the staff." Dr. Mahesh adds that before deciding whether to use an apron, it's important to check state regulations to ensure compliance.
8 Take a fluoroscopy timeout.
The Indiana Surgery Center North has instituted C-arm timeouts, which work sort of like a surgical timeout. "Before we take the shot, we take a moment to check if everything is in place and all personnel are properly protected," says Ms. Meier.
9 Check for safety features.
The FDA's Center for Devices and Radiological Health already requires that manufacturers incorporate certain safety features on C-arms; the agency is currently considering making features such as increased filtration and last-image-hold features mandatory as well. Here's a brief rundown on some C-arm features that affect the radiation dose.
- Last-image hold. This feature enables the operator to freeze the last image on the monitor after turning off the beam. It lets the clinician take time to study the image without exposing the patient to unnecessary radiation.
- Pulsed mode. In this mode, radiation is emitted in short pulses, providing images at 15 frames per second instead of the standard 30 frames per second, says Dr. Mahesh. It can be useful for orthopedic procedures, which don't typically involve imaging fast-moving body parts (such as the heart). When used properly, the pulsed mode can provide significant dose reduction, in some cases up to 40 percent. One caveat: The dose reduction only occurs if the radiation exposure is lower at the lower frame rates. If the operator sets the tube current too high in order to get high-quality images, it defeats the purpose of the pulsed mode, says Dr. Mahesh.
- Beam collimation. The C-arm's X-ray tube contains the collimator, which contains lead strips that size and shape the radiation beam. Tightly focusing the beam on the area of interest with the collimator improves image quality and decreases patient and staff exposure to radiation by limiting the amount of scatter, says Dr. Mahesh.
- Magnification and recording modes. These modes almost always increase the radiation dose, says Dr. Mahesh. He suggests using them only when appropriate and for as little time as possible.
- X-ray grids. Grids between the patient and the image intensifier help increase the contrast and the image quality by absorbing scatter from the patient while allowing the primary beam to pass through. This helps improve picture contrast and improves image quality. However, using a grid requires the operator to increase the radiation dose by a factor of two or more, says Dr. Mahesh. For smaller fields, thinner patients and pediatric patients, where there is less scatter to be removed, the operator may remove the grid without compromising on image quality.
With proper care
C-arms might be the most indispensable, widely-used pieces of surgical equipment in your facility. Use them properly and maintain them carefully, and they'll serve you steadfastly and safely for years to come.