![]() ![]() ![]() Interventionalists use the term “dose” on a daily basis and in a fairly casual fashion. The average interventionist may not use this terminology on a regular basis therefore, definitions and acronyms can become blurred, and terms can be used imprecisely. The IAEA also provides a document that can be printed out and posted in areas where fluoroscopy is used as a constant reminder of the appropriate radiation safety practices that should be used.Radiation safety is an important topic for interventionists, and one of the most confusing aspects of this field is the variety of terms that are used. The International Atomic Energy Agency (IAEA) addresses many of these issues in a "question and answer ( Q&A)" format. In radiation protection, we constantly emphasize the importance of maintaining radiation exposures "as low as reasonably achievable (ALARA)." Sometimes, there is too much emphasis on "low" and not enough consideration given to what is "reasonable." While it is true that your staff member who thinks she might become pregnant can eliminate the potential exposure to her unborn child by not participating in fluoroscopy procedures at all, is that a "reasonable" approach? A lead apron combined with other typical radiation safety practices, along with proper monitoring with a personnel monitoring badge should meet the ALARA concept, while still allowing that individual to participate in the procedures. Wearing a personnel monitoring badge under the lead apron at the waist will provide reasonable measurements of the radiation equivalent dose to a fetus. In terms of pregnant or potentially pregnant staff participating in fluoroscopy procedures, a "wrap-around" (i.e., covers all sides of the user) lead apron generally provides plenty of protection, especially when it is used in conjunction with other protection methods that you have suggested (e.g., stepping away from the patient during the exam). Leaded aprons, thyroid collars, and lead eyewear are very effective in reducing the scattered and leakage radiation to very low levels. Understanding the "backscatter" concept allows staff to position themselves in a location where the scattered radiation is lower. While the patient size and thickness is somewhat beyond the control of the machine operator, utilizing as small a field size as possible (referred to as "coning down") not only decreases the scattered radiation to the staff, but also reduces the area of the patient's skin exposed to x rays-a double benefit. That is where the scattered radiation is the highest. This is called "backscattered" radiation-think of it as the radiation "bouncing" off the patient in a backward direction. In fact, the area of highest scatter is on the same side where the x-ray beam enters the patient. Finally, the scattering angle is also important, mainly because people sometimes incorrectly assume that they should avoid standing on the opposite side of where the beam enters the patient because the x-ray beam would be "pointing" at them. Not surprisingly, as the field size increases, so does the scatter. Field size refers to the size of the radiation field where it enters the patient. It follows that if more radiation impinges on the patient, the amount of scattered radiation increases as well. Larger patients and thicker body parts require more radiation to produce an acceptable image for the physician. The scattered radiation at a specific location is affected by a number of factors including the patient (and machine parameters), the field size, and the scattering angle. By knowing what causes the variations in scatter, one can use that knowledge to minimize exposure. Of the two sources of exposure, it is the scattered radiation that varies considerably and is the higher contribution of exposure to the fluoroscopy staff. Regulations are in place that limit the amount of leakage radiation an x-ray tube can emit and all x-ray tubes must meet that limit when they are manufactured. Radiation exposure to staff involved in fluoroscopy procedures arises from two main sources-"scattered" radiation from the patient and "leakage" radiation from the x-ray tube. ![]()
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