Terminology, Positioning, and Imaging Principles C H A P T E R 1
Fig. 1-189 Thyroid shields with regular neck cutout apron.
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exposure under normal working conditions if recommended practices are followed. Therefore, with the possible exception of very busy interventionalists, eyeglasses with lenses containing lead offer no practical radiation protection value. Radiation-attenuating surgical gloves offer minimal protection of the operator’s hands, provide a false sense of protection, and are not recommended. The instantaneous dose from scatter radiation is reduced when the hands covered with one layer of glove material are located near the radiation field. However, the total time near the radiation field depends on the speed at which the procedure is performed as well as the distance from the imaged anatomy when the x-ray beam is activated. The increased thickness of these gloves reduces dexterity and can increase procedure time. The automatic exposure control system in fluoroscopy increases the radiation output to penetrate the glove when the hand is present in the beam. This can be confirmed by noting that anatomy is seen even though the glove is present. The dose to the hand is comparable to the dose when the radiation-attenuating glove is not present. The cost of radiation-attenuating surgical gloves and the minimal dose reduction do not justify the use of these devices according to the ALARA principle.
Image Wisely cutouts around the arms and low necklines. These allow greater exposure to the thyroid and breasts. Although some protective aprons have a thyroid shield built into them, most do not. A separate thyroid shield can be worn with the apron to protect the neck region (Fig. 1-189). Although a thyroid shield is not required for an individual participating in fluoroscopic procedures, a thyroid shield should be available (provided by the health care facility) for use at the option of the radiation worker. Wearing the thyroid shield is consistent with the ALARA principle, but the overall reduction in effective dose provided this device is small. For an individual approaching a significant fraction of the dose limit, the thyroid shield is recommended. The threshold for a vision-impairing cataract is at least 5.5 Gy (550 rad) accumulated in a period of more than 3 months. This threshold value exceeds the radiation dose that can be reasonably accumulated by the lens of the eye during a lifetime of occupational
Image Wisely is an awareness program, developed jointly by the American College of Radiology, Radiological Society of North America, American Association of Physicists in Medicine, and American Society of Radiologic Technologists, to promote radiation safety in adult medical imaging. The goal is to eliminate unnecessary radiation associated with adult imaging by avoiding non–medically indicated imaging procedures, by conducting the most appropriate imaging procedure, and by using the lowest optimal dose in all imaging practices. Printed and electronic educational resources have been developed for radiologists, medical physicists, radiologic technologists, referring physicians, patients, and the general public. Topics include dose, dose reduction techniques, appropriateness of imaging procedures, and risks. The information is directed at each respective target audience. A similar campaign, called Image Gently, is designed to minimize the radiation exposure in children, whose long life expectancy and increased radiosensitivity contribute to higher lifetime cancer risk.
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