At least 50% of an estimated 4-10 million interventional pain procedures are performed yearly in the U.S. under fluoroscopy using fluoroscopic imaging equipment, such as a Fluoroscopic C-arm. Most clinicians favor fluoroscopy, because it allows for a more exact needle placement, which ensures the accurate delivery of the injected drug. However, fluoroscopic guidance as an interventional technique does pose a radiation risk to patients, physicians, and anyone in close proximity. Rest assured, federal regulations place limitations on the maximum output for these C-arms. There are also a variety of techniques and methods for reducing the risk in the private practice setting.
Radiation Exposure: Understanding the Risk
The potential for any patient radiation is a valid and real concern that should be discussed and mitigated. Furthermore, we must always remember that the goal of all interventional radiology procedures is to treat (not harm) patients and improve their overall well-being. As a physician, any radiation risks that come with interventional procedures should be discussed with patients, especially when the possible amount of radiation could be high.
In normal conditions, fluoroscopy delivers roughly 5 rads per minute in the direct beam. The patient’s particular anthropometrics — which is the study of the variances in human sizes and measurements — can greatly determine the exposure rate. Specifically, the thickness of the patient is a variable that is known to greatly effect the exposure rate: the thicker the patient, the higher the exposure. Even small doses of radiation (1 rad = approximately one chance in 100,000) can cause damage to the DNA. The damage to the DNA caused by radiation has been associated with various health problems.
Shielding the patient is not always possible. This means that time and distance become critical in helping reduce the exposure. Time: shorter fluoro times can be achieved when the physician uses intermittent fluoroscopy (as opposed to continuous), and utilizes the image hold capacity. Distance: the patient’s exposure increases exponentially the closer he/she is positioned to the x-ray tube. Positioning the patient as far as possible from the x-ray tube (maybe 12 to 15 inches away from body), and as close as possible to the image intensifier, can lower exposure. (Decreasing x-ray field size can also reduce patient exposure).
With Fluoroscopic C-arms, knowledge and education are a must to properly monitor and reduce exposure levels to your patients and staff. You should receive training from a qualified expert (radiologist or radiological health physicist) on safety procedures and proper imaging techniques to minimize risk and future liability. Good safety practices, such as the ones below, can also keep radiation amounts As Low As Reasonably Achievable (ALARA).
Radiation Safety Guidelines
First and foremost, do not allow any unauthorized visitors during x-ray exams. Only individuals required for the radiographic procedure should be present in the radiographic room during exposures. Time, distance, and shielding are the three basic guides that could and should be taken for radiation safety:
- Timing. As we mentioned before, with timing, shorter fluoro times can be achieved when the physician uses intermittent fluoroscopy. Also, analyze original radiographs before performing a fluoroscopic examination. Viewing original radiographs, especially for orthopedic studies, can dramatically reduce the repeat rate for the time required for procedures.
- Distance. Observers should stand on the image intensifier side of the C-arm if possible, to avoid radiation leakage from the x-ray tube. When not assisting, step away from the patient during fluoro, as feasible. Stepping even one foot further back can significantly reduce a person’s dose. These are things to consider when calculating the size of the room for the C-arm.
- Shielding. In interventional fluoroscopy procedures, the tissue of concern is the skin. The skin that is at the site where radiation enters the body receives the highest dose than any other body tissue. All workers in the x-ray room during studies must have a lead apron, and other appropriate shielding wear.
Guide to Shielding
- Lead Apron and Thyroid Shields. Verify that the apron is 0.5 mm lead equivalent, and be sure aprons and shields are in good condition (remove any damaged ones). Insist on well fitting protective gear with a weight your body can handle. Hang aprons and shields on racks. Do not bend or fold them as this can cause cracks and tears in the protective material, making exposed body parts susceptible to radiation.
- Wrap-around Apron. When wearing lead aprons, it is imperative to keep the lead between you and the x-ray tube. Meaning, do not turn your unshielded back to the x-ray tube. If you do need to move about the room where exposing your back may be likely, insist on using a wrap around style apron.
- Leaded Eyeglasses. Those who routinely fluoro for long or interventional procedures, lead glasses with side shields can provide additional protection to the lens of the eyes. Remember, you may need to look sideways from the C-arm x-ray tube to see the image on the monitor, which will leave the lens unprotected if glasses do not have side shields.
- Leaded Gloves. Lead gloves are required if hands are potentially close to or in the primary beam.
Additional Safety Guidelines
- For needles, try using just one hand so you can keep your other hand away from the needle, and any potential exposure. Be sure there is ample lighting for accuracy. Properly dispose of used needles immediately after use.
- If possible, structural shielding (such as ceiling-mounted lead acrylic shield and an under-the-table shield) should be implemented.
- Always check for damages. If the C-arm or fittings are damaged, the x-ray tube and intensifier may become misaligned, resulting in image degradation or loss, as well as presenting a potential injury to the staff and patient.
- The fluoroscopy beam-on time and x-ray field size should be reduced as much as possible, and the x-ray beam kept well collimated. Failure of the x-ray beam collimation may lead to primary beam x-ray exposure outside of the selected image intensifier input area. This would result in image degradation and additional exposure for the patient.
- Pulsed fluoroscopy, single pulse fluoroscopy mode, manual mode, fluoroscopy timer warning, and last image hold (“freezing the screen”) are also good safety practices.