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Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards (2015)

Chapter: Appendix B: Glossary, Acronyms, and Abbreviations

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Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
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B

Glossary, Acronyms,
and Abbreviations

AAPM American Association of Physicists in Medicine
absorbed dose The amount of energy from ionizing radiation deposited at a given point. Absorbed dose is measured in Gray.
advanced imaging technology (AIT) Technology is intended to screen passengers at airports or other secure facilities (such as prisons) that allow for visual detection of both metallic and non-metallic threat items, including weapons, explosives, and other concealed objects on passengers. These items would not be detected by walk-through metal detectors.
air kerma Radiation quantity often used to express the radiation concentration delivered to a point, such as the entrance surface of the body. It is measured in joules/kilogram (J/kg).
ALARA as low as (is) reasonably achievable
ANSI American National Standards Institute
AS&E American Science and Engineering, Inc.
ATR automatic target recognition
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
backscatter The reflection of waves or signals back to the direction from which they came.
BMI body mass index
bystanders Persons—for example, operators or persons waiting in line to be scanned—not being scanned but who may receive dose from the operation of the backscatter X-ray machine because of their proximity to the inspection area.
CDC Centers for Disease Control and Prevention
CPE charged particle equilibrium
DDE deep dose equivalent
DHS Department of Homeland Security
effective dose Effective dose is a dose parameter that takes into consideration the type of radiation and the sensitivity of the body parts exposed. Effective dose is expressed in sieverts (Sv).
EMO emergency-off (button)
FAT factory acceptance test
FDA Food and Drug Administration
HPS Health Physics Society
HVL half-value layer
ICRP International Commission on Radiological Protection
ICRU International Commission on Radiation Units and Measurements
interlocks Systems (devices or processes) used to prevent failure of a machine. Interlocks can be electrical, mechanical, or software.
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
JHU/APL Johns Hopkins University/Applied Physics Laboratory
KERMA kinetic energy released in matter (known as kerma)
Linear-nonthreshold (LNT) dose reponse model of radiation effects Model used for radiation protection purposes to estimate risks at low radiation doses where there is not sufficient epidemiological or biological evidence to draw direct conclusions about risks. The linear nonthreshold model assumes that there is a linear relationship between dose and effect and therefore allows for extrapolation from the outcomes observed at higher radiation doses to lower doses.
NCRP National Council on Radiation Protection and Measurements
NIST National Institute of Standards and Technology
NRC National Research Council
NURBS Non-Uniform Rational Basis Spline
organ dose The absorbed dose averaged over an organ. Organ dose is measured in Gray.
OSHA Occupational Safety and Health Administration
OSL optically stimulated luminescence
PDD percent depth dose
primary and secondary screening Primary screening is screening that all passengers are subject to. Secondary screening is additional screening that may be used based on the response to the primary screening, randomization, or other metrics that suggest that further information is needed about a passenger (e.g., to possibly resolve an alarm during primary screening).
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
radiation The energy that comes from a source and travels through some matter or through space. There are two types of radiation: ionizing and nonionizing. Ionizing radiation, which includes X-rays, is considerably more energetic compared to nonionizing radiation such as that found in microwaves. Ionizing radiation is more harmful to living organisms per unit of energy deposited than is nonionizing radiation as it has the potential to cause DNA damage and, consequently, cancer. Currently, there is no convincing evidence that nonionizing radiation can cause cancer, with few exceptions; for example, ultraviolet and skin cancer.
RFP request for proposals
SAT site acceptance test
scan The operation necessary to produce one image (e.g., front view) from one radiation source. One radiation source simultaneously producing multiple images also constitutes one scan. Two sources simultaneously producing two images constitute two scans. In some cases several scans may be required for a single screening of the subject.
screening The sum of radiation exposures or scans necessary to image objects concealed on all sides of the body as intended by the system design under normal conditions. Examples: (1) for backscatter systems a screening typically consists of four scans, one from each side; (2) for transmission systems a screening typically consists of one scan.
SDE shallow dose equivalent
Sievert (Sv) The international (SI) name for the unit of dose equivalent radiation measured in J/kg, calculated by multiplying the absorbed dose (in Gy) with a weighting factor.
SP single pose
SSD source-skin distance
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
TMR tissue-maximum ratio
TSA Transportation Security Administration
TSIF Transportation Systems Integration Facility
uncertainty Lack of sureness or confidence in predictions of models or results of measurements (NCRP Report No. 158).
USAPHC U.S. Army Public Health Command
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
Page 158
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
Page 159
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
Page 160
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
Page 161
Suggested Citation:"Appendix B: Glossary, Acronyms, and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2015. Airport Passenger Screening Using Backscatter X-Ray Machines: Compliance with Standards. Washington, DC: The National Academies Press. doi: 10.17226/21710.
×
Page 162
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Passenger screening at commercial airports in the United States has gone through significant changes since the events of September 11, 2001. In response to increased concern over terrorist attacks on aircrafts, the Transportation Security Administration (TSA) has deployed security systems of advanced imaging technology (AIT) to screen passengers at airports. To date (December 2014), TSA has deployed AITs in U.S. airports of two different technologies that use different types of radiation to detect threats: millimeter wave and X-ray backscatter AIT systems. X-ray backscatter AITs were deployed in U.S. airports in 2008 and subsequently removed from all airports by June 2013 due to privacy concerns. TSA is looking to deploy a second-generation X-ray backscatter AIT equipped with privacy software to eliminate production of an image of the person being screened in order to alleviate these concerns.

This report reviews previous studies as well as current processes used by the Department of Homeland Security and equipment manufacturers to estimate radiation exposures resulting from backscatter X-ray advanced imaging technology system use in screening air travelers. Airport Passenger Screening Using Backscatter X-Ray Machines examines whether exposures comply with applicable health and safety standards for public and occupational exposures to ionizing radiation and whether system design, operating procedures, and maintenance procedures are appropriate to prevent over exposures of travelers and operators to ionizing radiation. This study aims to address concerns about exposure to radiation from X-ray backscatter AITs raised by Congress, individuals within the scientific community, and others.

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