Since Wilhelm Conrad Röntgen revealed the power of cathode rays and X-rays in 1895, physicians and surgeons have expanded the use of X-rays as a valuable clinical tool. Today, X-rays are used in single frame radiographs, computed tomography (CT), radiotherapy, and real-time fluoroscopy. Each of these modalities has improved accuracy in diagnosing clinical conditions, locating foreign bodies, allowing placement of percutaneous devices, and, in the case of radiotherapy, treating diseases.
In the early 20th century, scientists like Hermann Muller began to show the harmful, long-lasting effects of X-ray radiation. His 1926 paper outlined the potential for deleterious mutational effects on DNA. It has become evident that X-ray radiation can cause a host of secondary diseases, including malignancy, burns, and cataracts.
In 1928, the International Commission on Radiological Protection (ICRP) was formed to provide recommendations and guidance on protection against the risks associated with ionizing radiation. The commission, through extensive research and review, determines safe practices involving radiation and offers dose-limit guidance for patients and employees commonly exposed to radiation. The ICRP recommendations are dynamic and change as new evidence is discovered, often through observational studies such as those focusing on the victims of the atomic bomb or occupational exposures.
Limiting patient exposure
Orthopaedic surgeons rely on radiographs and CT scans for diagnosis and preoperative planning. As physicians, we must actively engage in practices that keep patients safe from exposure and minimize cumulative radiation dosages. This begins with ordering only the radiology tests essential for patient care. Remember, a single CT scan may provide a radiation dose up to 7 times the recommended maximum annual patient exposure.
Body parts known to be sensitive to radiation should be shielded whenever practical. These include the thyroid, gonads, and eyes.
Finally, it is our duty to stop ordering repeat radiographic tests simply because the studies are not available for review or in our own picture archiving and communication system. We should do everything possible to have the patient bring all previous studies and attempt to integrate them into our system before ordering another test. As treating physicians, we are responsible for doing all we can to eliminate unnecessary tests.
Limiting surgeon/surgical team exposure
The safety of the physician and healthcare team is also important. As orthopaedic surgery becomes more reliant on fluoroscopy due to the percutaneous nature of newer, minimally invasive procedures, surgeons should be cognizant of safety recommendations.
Studies have recommended that surgeons and others in the radiation field wear 0.5 mm lead-equivalent aprons during fluoroscopy (Fig. 1). Those whose backs are to the fluoroscope during activation should wear aprons with closed backs. Because the thyroid is very sensitive to ionizing radiation, thyroid shields should be worn anytime fluoroscopy is used. Personnel who are wearing leaded glasses should orient their heads to avoid exposing the sides to the radiation.
When hands are directly exposed to the radiation beam, exposure is markedly increased, so surgeons should always attempt to keep their hands out of the field of view when using the fluoroscope. If the surgeon’s hands must be exposed, leaded gloves or bismuth-based x-ray attenuating hand creams can provide some protection.
Closing the collimator down increases the concentration of exposure to the patient’s skin but also reduces the surface area of exposed skin and decreases scatter from the fluoroscope. Surgeons should always use the lowest possible kVp setting to achieve satisfactory images.
Placing leaded shields on stands or hanging them from the ceiling, when possible, can decrease radiation exposure to the patient, the surgeon, and other personnel.
The generator should be positioned as far away from the patient and surgeon as possible to reduce exposure. To avoid receiving an increased dose of radiation due to scatter, the surgeon and other personnel should stand on the image-intensifier side of the fluoroscope, not the generator side. All radiology staff should wear detection badges that calculate dose limits, and the badges should be read and updated regularly.
Radiation equipment options
C-arm selection is important when determining the risks of ionizing radiation with fluoroscopy. A 2005 study showed that the radiation exposure from a mini C-arm was one to two orders of magnitude lower than with the larger C-arm. Whenever possible, a mini C-arm should be used to provide adequate imaging.
Lead aprons must be properly maintained to ensure their protective efficacy. Lead aprons should be hung properly—never folded—when not in use. Lead can fracture during folding and allow harmful radiation to penetrate and injure the wearer. Aprons should also undergo annual or semi-annual quality control tests to ensure they are working properly.
Newer radiation protection is available in several forms but is not yet in widespread use. A 2006 study that tested three forms of radiation-protective gowns found that only one offered the same protection as lead. The others only offered equal protection at frequencies lower than those used most. All three, however, were lighter and more comfortable than lead.
In 2012, the ICRP focused on ocular exposure to ionizing radiation because new evidence confirmed that radiation exposure leads to cataract formation and posterior lens opacities. Despite the fact that a recent study found a greater than 90 percent reduction in the lens exposure to harmful ionizing radiation with the use of leaded eyeglasses, many orthopaedic surgeons do not wear leaded eyeglass protection during cases requiring fluoroscopy.
Orthopaedic surgeons are relying more heavily on X-rays, CT scans, and fluoroscopy during advanced procedures. For this reason, we must be well versed in the safety concerns of all forms of ionizing radiation. Many measures exist to protect the patient, surgeon, and medical personnel from the harmful effects of radiation. Each situation involving X-ray radiation should be carefully evaluated to limit adverse effects, and ICRP guidelines should be followed to prevent potential harm to healthcare providers and patients.
Bradford S. Waddell, MD, and William J. Robb III, MD, are members of the AAOS Patient Safety Committee. Jeffrey E. Martus, MD, is assistant professor, orthopaedics and rehabilitation, and assistant professor, pediatrics, at the Vanderbilt University Medical Center; Paul Zemaitis, MPH, is a regulatory analyst in the AAOS department of research and scientific affairs.
- Badman BL, Rill L, Butkovich B, Arreola M, Griend RA: Radiation exposure with use of the mini-C-arm for routine orthopaedic imaging procedures. J Bone Joint Surg Am 2005;87(1):13-17. http://dx.doi.org/10.2106/JBJS.D.02162
- Scuderi GJ, Brusovanik GV, Campbell DR, Henry RP, Kwon B, Vaccaro AR: Evaluation of non-lead-based protective radiological material in spinal surgery. Spine J 2006;6(5):577–582.http://dx.doi.org/10.1016/j.spinee.2005.09.010
- Burns S, Thornton R, Dauer LT, Quinn B, Miodownik D, Hak DJ: Leaded eyeglasses substantially reduce radiation exposure of the surgeon's eyes during acquisition of typical fluoroscopic views of the hip and pelvis. J Bone Joint Surg Am 2013;95(14):1307–1311. doi: 10.2106/JBJS.L.00893.
Dose terminology and units
The radiation energy absorbed per unit mass is called the absorbed dose and is dependent upon the tissue type (ie, skin or bone). The units of absorbed dose are expressed in joules (J) per kilogram, where 1 J/Kg = 1 gray (Gy) = 100 rad.
Equivalent dose describes the potential biologic damage that may result from different radiation types and is calculated by multiplying the absorbed dose by the radiation weighting factor (WR) of the radiation type. The radiation types used in diagnostic radiology and nuclear medicine (X-rays, gamma rays, and beta particles) have a WR of 1, whereas alpha particles have a WR of 20. Equivalent doses are used for radiation protection purposes and are expressed in sieverts (Sv) or roentgen equivalent in man (rem), where 100 rem (or 1 Gy) is equivalent to 1 Sv (1 mrem = 0.01 mSv).
Because most radiologic studies provide a nonuniform dose distribution within the patient and because organs vary in radiosensitivity, an effective dose can be calculated to provide a comparative uniform whole-body dose that has the same risk as a particular nonuniform dose distribution. The effective dose is calculated by the summation of the product of the equivalent dose for each exposed organ and the organ weighting factor (w). The weighting factors (w) range from 0.01 for skin and bone surfaces to 0.04 for thyroid, 0.08 for gonads, and 0.12 for bone marrow. The formula for determining the effective dose is as follows:
T = Tissue or organ of interest
WT = Tissue Weighting Factor
HT = Equivalent Dose absorbed by tissue T
People are exposed to radiation every day, primarily from naturally occurring radioactive materials such as radon gas from soils and cosmic radiation from the atmosphere. The average person experiences approximately 2 mSv to 3 mSv per year from these sources. A simple chest X-ray has an approximate radiation dose of 0.1 mSv. A CT scan of the chest delivers a dose of up to 7 mSv. An extremity radiograph has a radiation dose of 0.001 mSv; a spine radiograph has a dose of approximately 1.5 mSv.
In 2007, the ICRP made the following recommendations for physicians and patients:
- a maximal occupational exposure of 20 mSv per year, averaged over 5 years with no single year greater than 50 mSv
- a patient exposure of no more than 1 mSv per year from medical sources
- a maximum lifetime occupational exposure of 1 Sv, or 1000 mSv
In 2008, the ICRP estimated the incidence of fatal cancer from radiation exposure at 4 percent per Sv, when averaged across gender and age.
In 2012, the ICRP lowered the annual occupational threshold for ocular ionizing radiation exposure from 150 mSv per year to 20 mSv averaged over 5 years with no single year having more than 50 mSv exposure. The exposure potentially necessary to form cataracts is 0.5 Gy.