Exposure
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EXPOSURE
# Springer-Verlag GmbH Germany, part of Springer Nature 2020
Guidance on using shielding on patients for diagnostic radiology applications. A joint report of the British Institute of Radiology, Institute of Physics and Engineering in Medicine, Public Health England, Society & College of Radiographers, and the Society for Radiological Protection. March, 2020. https://www.bir.org.uk/media/414334/final_patient_ shielding_guidance.pdf This consensus document is supported by evidence-based research on patient-contact shielding. The authors concluded that contact shielding provides minimal or no benefit in diagnostic and interventional radiology, can adversely interfere with imaging, and can result in increased radiation exposure from repeat examinations or interference with automatic dose controls. They recommended cessation of all patient-contact shielding including gonadal, eye, thyroid and breast shielding. In the past, gonadal shielding was used to protect against concerns for heritable disease. In the United Kingdom, the mean entrance surface dose for pelvic radiographs has been reduced 60-fold since 1904, 6-fold between 1958 and 2010. Further, there is no evidence that radiation exposure results in excess of heritable disease in humans. Thus, the main reason to use contact shielding is to reduce the risk of carcinogenesis or radiation-induced posterior subcapsular cataracts. Rather than focus on contact shielding, the authors argued for “as low as reasonably practicable” (ALARP), balancing the risks and benefits by optimizing the examination. Contact shielding best protects against the primary beam and not secondary sources of radiation including scatter; however, shielding can interfere with the automatic dose control, increasing dose, or obscuring pathology and necessitating repeat exposure. Reject analysis should include causes of reject from shielding. Ovarian shielding is also problematic because the ovaries’ exact location is variable within the pelvis. Collimation is one way to optimize the examination because the primary radiation drops to 1% at 25 mm from the edge of the collimator. Secondary sources include tube leakage, scatter from collimator housing, extra-focal radiation, internal scatter from irradiated tissue, and backscatter. Internal scatter is the major source of secondary radiation to organs and is not reduced by contact shielding. Specific recommendations for radiography,
fluoroscopy, interventional radiography, CT, mammography and dental radiography are addressed. Pregnant patients and pediatric patients are discussed by modality. The document is an excellent review of the research, with literature citations supporting the recommendations along with simple steps to optimize radiation protection for different types of examination and modalities. Finally, because patients might expect shielding, there is a chapter discussing communications and a separate, downloadable frequently-asked-questions brochure for patients (https://www.bir.org.uk/media/427407/ bir_patient_shielding_folded_
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