Which radiation safety measures are needed during therapeutic injections for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

To measure the effective dose (whole body dose) from occupational radiation exposure, the measure termed rad is converted to the unit of occupational exposure, which is designated as the radiation-equivalent-man (REM). The unit of dose equivalent to REM is measured by using the sievert (Sv); one REM is equivalent to 1 rad, and 100 REM is equivalent to 1 Sv. Radiation dose equivalents of 0.25 Sv (25 REM) may lead to measurable hematologic depression. Whole body total radiation doses exceeding 100 REM may lead to nausea, fatigue, radiation dermatitis, alopecia, testicular disturbance, and hematologic disorders.

A maximal permissible dose (MPD) is the upper limit of the allowed radiation dose that an individual may receive without the risk of significant side effects. The annual whole body MPD limit for physicians is 50 mSv. The annual MPD for the lens of the eye is 150 mSv, and for the thyroid, gonads and extremities it is 500 mSv. The fluoroscopy's x-ray tube should be kept as far away from the patient as possible. Federal regulations limit the maximum output for C-arm fluoroscopy to 10 R/min at 12 in (30 cm) from the image intensifier. Beam collimation reduces the area being irradiated, thereby reducing the amount of x-rays received by the patient. The use of live fluoroscopy should be minimized as much as possible. Furthermore, magnification should be limited since it increases the amount of radiation to human tissue. Image magnification by a factor of 2 increases the amount of radiation by 4 times.

Radiation exposure to ionizing radiation is unavoidable when performing fluoroscopic procedures. Only necessary personnel should be present in the fluoroscopy room. The primary source of radiation to the practitioner during such procedures is from scatter that is reflected back from the patient. Less prominent is the role of radiation leakage from the equipment. The cardinal principals of radiation protection are (1) maximize the distance from the radiation source, (2) use shielding materials, and (3) minimize exposure time. Radiation scatter can also be reduced by using the lowest tube current (mA) that is compatible with a good x-ray image. In conventional fluoroscopy, the x-ray tube is located beneath the table and the image intensifier is above the table.

With a horizontal table, in this arrangement, most of the radiation scatter is in a downward direction and is absorbed into the floor or side panels of the table. In the opposite arrangement, it is often difficult to get adequate shielding to medical personnel. As mentioned, the beam-on time is the most important variable for controlling radiation exposure and should be kept to a minimum; most fluoroscopy machines are armed with a 5-minute alarm.

X-ray shielding can be fixed or mobile, including the commercially available protective apparel. Fixed shielding includes the thickness of walls, doors, and protective cubicles, which should have a lead equivalent of 1-3 mm. Mobile shielding is appropriate during fluoroscopy when a member of the staff needs to remain near the patient. Specific items of apparel that are used for personal shielding include lead aprons, gloves, thyroid shields, and glass spectacles.

Typically, practitioners and assisting personnel are supplied with monitoring equipment in the form of a radiation or film badge that is packed with photographic film. These clips are typically light and slim for convenient placement on conventional clothing and apparel. Usually a "color badge" is worn outside the apron on the upper portion of the body, usually on the upper edge of the thyroid shield. This badge approximates radiation exposure to the lens of the eye. A second "behind the apron" badge is worn underneath lead apparel and clipped onto the waist of the practitioner. X-ray readings from this badge represent the actual dose to the gonads and major blood-forming organs.

Also, a finger or ring badge can be worn with the film facing the underside part of the hand nearest the radiation source. Badges may also be placed on protective eyewear. These badges are usually processed monthly to monitor the type and amount of radiation exposure received by each clinical participant. Results are reported as monthly and 12-month accumulated dosages. Prompt exchange of badges on a monthly basis is required in most medical facilities.


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