Personnel Protection

Personnel Protection

Radiographers must avoid unnecessary radiation exposure to themselves and strive to keep patient dose to an absolute minimum. The sources of radiation exposure to the radiographer are the primary beam and secondary radiation (scatter and leakage). Radiographers must never be exposed to the primary, or useful, x-ray beam.

Radiographers must follow the ALARA (as low as

reasonably achievable) principle as they carry out their tasks. New radiologic staff participates in radiation safety orientation, and regular inservice education on radiation safety is conducted. Proper radiation monitoring and review of monthly radiation reports is essential.

 SCATTERED RADIATION

When primary x-ray photons intercept an object and undergo a change in direction, scattered radiation results.

INVERSE SQUARE LAW

Reducing the length of time exposed to ionizing radiation, results in a reduction of occupational exposure. Increasing the distance from the source of radiation, as illustrated by the inverse  square law. Placing a barrier, like a lead wall or lead apron, between you and the source of radiation results in a reduction of occupational exposure. We must minimize the time of exposure to the source of radiation, provide effective shielding from the radiation source, and, most importantly, maximize the distance from the source

of radiation.

GUIDELINES

Primary radiation barriers protect against direct exposure from the primary (useful) x-ray beam and have much greater attenuation capability than secondary barriers, which protect only from leakage and scattered radiation. Examples of primary barriers are the lead walls and doors of a radiographic room, Primary protective barriers of typical installations generally consist of walls with 1/16 inch (1.5 mm) lead thickness and 7 feet high. Secondary radiation is defined as leakage and/or scattered radiation.

The x-ray tube housing protects from leakage radiation as stated previously. The patient is the source of most scattered radiation.

PROTECTIVE APPAREL AND ITS CARE

During fluoroscopic procedures requiring the radiographer’s presence in the radiographic room, the radiographer must wear protective apparel, to include a lead apron, lead aprons must provide the equivalent of at least 0.50 mm Pb, and lead gloves at least 0.25 mm Pb equivalent. Other useful protective apparel includes thyroid shields, Lead aprons, lead gloves, and other apparel are secondary barriers; they will not provide protection from the useful beam. Proper care of protective apparel is essential to ensure effectiveness. Lead aprons and gloves should be hung on appropriate racks,not dropped on the floor or folded. Careless handling can result in formation of cracks. Lead aprons and gloves should be imaged annually(either fluoroscopically or radiographically) to check for cracks.

 PROTECTIVE ACCESSORIES

Another device available for individuals required to remain in the fluoroscopy room is a mobile leaded barrier. Mobile barriers provide full body protection from scattered radiation and are available in a variety of lead equivalents.

SPECIAL CONSIDERATIONS

PREGNANCY

Deserving special consideration in protection from occupational exposure is the pregnant radiographer. As soon as the radiographer knows she is pregnant, it is advisable that she declare her pregnancy in writing. At that time, her occupational radiation history will be reviewed. The gestational dose limit to the fetus during the gestation period must not exceed 500 mrem (5 mSv)

MOBILE UNITS

Each mobile x-ray unit should have a lead apron assigned to it. The radiographer should wear the apron while making the exposure at the furthest distance possible from the x-ray tube. The mobile unit’s exposure cord must permit the radiographer to stand at least 6 feet from the x-ray tube and patient. In mobile fluoroscopic units, there must be a source to patient skin distance of at least 12 inches.

FLUOROSCOPIC UNITS AND PROCEDURES

All fluoroscopic equipment must provide at least 12 inches (30 cm), and preferably 15 inches (38 cm), between the x-ray source (focal spot) and the x-ray tabletop (patient). The tabletop intensity of the fluoroscopic beam must not exceed10 R/min or 2.1 R/min/ma. With under table  fluoroscopic tubes, a Bucky-slot closer/cover having at least the equivalent of 0.25 mm Pb must be available to attenuate scattered radiation. Fluoroscopic mA (milliamperes) must not exceed 5, image-intensified fluoroscopy usually operates between 1 and 3 mA. Because the image intensifier functions as a primary barrier, it must have a lead equivalent of at least 2.0 mm. A cumulative timingdevice must be available to signal the fluoroscopist (audibly, visibly, or both) when a maximum of 5 minutes of fluoroscopy time has elapsed.Beam collimation must be apparent through visualization of unexposed borders on the TV monitor, and total filtration must be at least 2.5 mm Al equivalent. Because occupational exposure to scattered radiation is of considerable importance in fluoroscopy, a protective curtain/drape of at least 0.25 mm Pb equivalent must be placed between the patient and fluoroscopist. As in radiography, high kV andlow mAs(milliampere-seconds) values are preferred in an effort to reduce dose.