Advanced Imaging Technology: "Radiation Risk Tiny"

You may have read a recent article stating that Advanced Imaging Technology used at TSA checkpoints is not safe. Because of the discussion the article has created, I wanted to share this with you.

The American College of Radiology posted an article titled: ACR Statement on Airport Full-body Scanners and Radiation and then WebMD followed up with an article titled New Airport Scanners: Radiation Risk Tiny which quoted the ACR article.

From the ACR article: "An airline passenger flying cross-country is exposed to more radiation from the flight than from screening by one of these devices. The National Council on Radiation Protection and Measurement (NCRP) has reported that a traveler would need to experience 100 backscatter scans per year to reach what they classify as a Negligible Individual Dose. The American College of Radiology (ACR) agrees with this conclusion. By these measurements, a traveler would require more than 1,000 such scans in a year to reach the effective dose equal to one standard chest x-ray."

"The ACR is not aware of any evidence that either of the scanning technologies that the TSA is considering would present significant biological effects for passengers screened."

We also asked the Johns Hopkins University of Applied Physics Laboratory to perform an independent radiation safety engineering assessment of our Advanced Imaging Backscatter Technology and they determined that the radiation dose to scanned individuals from this general use system is within the requirements of ANSI N43.17 2002 and 2009.

In the coming weeks, the FDA will be posting similar information on their web page.

For your reference:

Backscatter technology projects an ionizing X-ray beam over the body surface at high speed. The reflection, or "backscatter," of the beam is detected, digitized and displayed on a monitor. Each full body scan produces less than 10 microrem of emission, the equivalent to the exposure each person receives in about 2 minutes of airplane flight at altitude. It produces an image that resembles a chalk-etching.

Millimeter wave technology bounces harmless electromagnetic waves off of the human body to create a black and white image (not a photograph). It is safe, and the energy emitted by millimeter wave technology is the energy projected by the system is thousands of times less intense than a cell phone transmission. This technology is not new. TSA is not the first to use this technology. It's currently being used in Canadian airports and U.S. courthouses in Colorado and Texas as well as international locations.

This Standard limits the reference effective dose2 delivered to the subject to 0.25 microsieverts (25 microrem) per screening.

For your reading pleasure, here are some documents relevant to security screening of humans using ionizing radiation:

ANSI/HPS N43.17-2009 Radiation Safety for Personnel Security Screening Systems Using X-Ray or Gamma Radiation

NCRP commentary 16, Screening of humans for security purposes using ionizing radiation scanning systems

NCRP Statement 10, Recent Applications of the NCRP Public Dose Limit Recommendation for Ionizing Radiation (2004)

NCRP report no. 116 Limitation of Exposure to Ionizing Radiation (1993) ISBN 0-929600-30-4 recommends annual limits on radiation dose for the general public. Report 116 also introduces the concept of a negligible individual dose.

NCRP report no. 160, Ionizing Radiation Exposure of the Population of the United States (2009)

Screening Individuals with Backscatter X-Ray Systems by Daniel Strom

HPS Position Statement Use of Ionizing Radiation for Security Screening Individuals

HPS Public Information Radiation Exposure During Commercial Airline Flights

American College of Radiology (ACR) Statement on Airport Full-body Scanners and Radiation

EPA.gov Ionizing Radiation

Information on laws and regulations applicable to manufacturers of people screening security systems that use x-rays is on FDA's X-Ray & Particulate Products other than Medical Diagnostic or Cabinet page.

ANSI/HPS N43.17 is not a mandatory standard. More information on the ANSI standards setting process is available on the ANSI website.

The concept of justification based on a societal benefit appears in the International Commission on Radiological Protection (ICRP) report 60 (see paragraph S14).

Random Facts:

For comparison, the energy projected by millimeter wave technology is 10,000 times less than a cell phone transmission.

We, and all objects around us, generate millimeter wave energy - and we are exposed to it every single day.

Backscatter technology uses low level X-ray and a single scan is the equivalent of two minutes of flying on an airplane.

Full Body Scanners at Security Okay by Travelers - When it comes to the newest addition to airport security, 79 percent of travelers said they are comfortable with U.S. airports using full body scanners that can see through clothes.

We've written many posts on Advanced Imaging Technology and you can read them all HERE.

Blogger Bob
TSA Blog Team

Response to: “Oops: Backscatter X-ray machines tear apart DNA"

This article has been receiving quite a bit of attention and it’s leading people to believe the Backscatter Advanced Imaging Technology (AIT) used by TSA emits terahertz radiation. Recent studies are showing that terahertz radiation may “unzip double-stranded DNA, creating bubbles in the double strand that could significantly interfere with processes such as gene expression and DNA replication.”

(I know… who knew that your DNA could be unzipped? Hey buddy, your barn door’s open!!!)

I forwarded the article around to a few subject matter experts here at TSA and was provided with some interesting information:

“TSA has not tested nor procured any terahertz AIT systems.”

That sentence should sum it up for most of our readers, but for those who like to get into the weeds, here is some more interesting information that was given to me from the fine folks at the Office of Security Technology (OST):

The Transportation Security Administration (TSA) has assessed multiple types of AIT systems including X-ray backscatter and millimeter wave. Both offer safe and effective whole body screening for weapons and explosives concealed on a person’s body. Backscatter X-ray technology uses X-rays that penetrate clothing, but not skin, to create an image. Millimeter wave technology uses sensors to collect millimeter wave energy to measure the difference in radiated energy relative to each object against a common background (the human body produces these signatures in typical screening applications) to construct a composite image.

Backscatter - Relies on a narrow, low intensity X-ray beam scanned over the body’s surface at high speed that is reflected back from the body and other objects placed or carried on the body, where it is converted into a computer image of the subject and displayed on a remote monitor. For comparison purposes, the X-ray dose received from the backscatter system is equivalent to the radiation received in two minutes of airplane flight at altitude (0.003* millirem by backscatter (2 scans) compared to .0552 millirem for two minutes of flight). Newer technologies require less scanning time, reducing individual X-ray exposure to .002 millirem for the entire process. The backscatter AIT meets and exceeds the American National Standards Institute (ANSI) standard for personnel security screening systems using X-rays.

Millimeter Wave - Uses non-ionizing radio frequency energy in the millimeter wave spectrum to generate an image based on the energy reflected from the body. The frequency range for millimeter wave technology exists in the range between 30-300 gigahertz. The three-dimensional image of the body is displayed on a remote monitor for analysis. The energy projected by the system is 10,000 times less than a cell phone transmission (.00000597 mW/cm2 for millimeter wave technology compared to 37.5 mW/cm2 for a cellphone).

Other Safety Information

“TSA security screening technologies are required to meet consensus standards, such as those issued by the American National Standards Institute (ANSI), as well as regulatory requirements such as those issued by the Food and Drug Administration (FDA). Our systems are independently tested as well by such laboratories as Johns Hopkins Applied Physics Laboratory (APL) and the National Institute for Standards and Technology (NIST) and FDA. We also apply an aggressive maintenance program to ensure that these systems continue to meet these performance standards. Additionally, TSA Occupational Safety Health and Environment (OSHE) is an active participant in our project integrated project teams. TSA OSHE assists in the development and validation of technology safety requirements. We also conduct safety evaluations as part of our laboratory, TSA Systems Integration Facility (TSIF), operational and site acceptance testing procedures.”

TSA tells its employees, namely Transportation Security Officers (TSOs), about the safety of advanced imaging technology machines, including the radiation exposure, during training on the equipment. In addition, TSA’s Office of Occupational Safety Health and Environment has individuals who work directly with TSOs to communicate safety information about operating the equipment. Information is available to TSOs through the OSHE Web site and employees can contact members of OSHE directly with questions.

*.04 was posted in error. The corrrect number was added. 0.003 millirem. Edited on 1/5/10

Thanks,

Blogger Bob

TSA Blog Team