Radiation exposure can lead to injury via deterministic or stochastic effects. Deterministic effects are dose-related damage to tissue, such as skin burns, hair loss, radiation sickness, cataract formation, and congenital abnormalities of fetuses that were exposed to radiation. Stochastic effects are observed in the statistically increased risk of cancer due to radiation exposure. This risk is not directly dose-related, but a higher cumulative lifetime dose increases the risks of radiogenic cancer.
During angiography, x-ray beams are emitted from the x-ray generator and directed through the patient and angiography table towards the image intensifier (Fig. 19.1). The majority of the radiation passes between the generator and the image intensifier, but when the x-ray beams hit the patient and table, radiation scatter occurs and impacts the surrounding healthcare workers.
Fig. 19.1
X-ray generator and image intensifier
The amount of radiation employed during a given procedure varies significantly between operators. Diligent radiation management by the operator can produce the greatest modification of the radiation exposure to the patient and healthcare staff. Before starting the procedure, the interventionalist operating the fluoroscopy pedal should ensure that all members of the healthcare team are wearing adequate protective equipment. Healthcare workers operating within 4 feet of the image intensifier should wear a two-piece 0.5 mm lead equivalent apron, thyroid shield, and leaded glasses. A radiation dosimeter should be worn to ensure that personnel exposure remains below allowable limits. There should be routine monitoring and feedback of dosimetry results. A movable below-table lead skirt and ceiling-mounted leaded glass shield should be used to block and reduce scatter exposure (Fig. 19.2).
Fig. 19.2
Angiography suite with below-table lead skirt and ceiling-mounted shield
The operator should use fluoroscopy only when looking at the image and should make liberal use of last-frame hold to review imaging. Use of magnification should be minimized when possible, because magnification generates higher radiation doses. Pulse fluoroscopy should be used in place of cine fluoroscopy whenever possible. Cine runs are automatically stored, but pulse fluoroscopy runs are not, so the operator should be sure to store the run if he or she wishes to save it for later review. For cine fluoroscopy, the lowest frames per second that achieves adequate image quality should be used. Careful timing of contrast injection also can decrease the duration of cine fluoroscopy runs. The power injector has an option for radiation delay. For example, if the tip of the catheter is in the common femoral artery and the tibial arteries are being imaged, a 2-second radiation delay allows time for the contrast to reach the target vessel, minimizing radiation exposure. Longer radiation delays are needed if significant arterial occlusive disease is present. Maintaining the image intensifier as close to the patient as possible also decreases scatter and maximizes the image area. Positioning the patient closer to the x-ray generator decreases scatter radiation but increases the dose to the patient. Collimation—shutters to limit the x-ray field—should be utilized whenever possible (Fig. 19.3). Collimation should exclude areas at the far ends of the exposure spectrum (air, metal) and allow enough context for image identification afterwards.
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