Difference between Medical and Airport scanner radiation

Difference between Medical and Airport scanner radiation

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What is the difference between radiation doses of a medical scanner and airport security scanner (X-Ray full body scan)? Is it the same kind of radiation? Does it pose any danger for people who fly often?

The type of radiation is quite different in a medical X-ray vs. an airport scanner.

Medical X-rays are high frequency (beyond ultraviolet) radiation, typically on a wavelength of a few angstroms. While I would emphasize that @Ram is right to point out that there is not very much radiation in a medical X-ray since electronic detectors have been in place over film, the radiation itself is capable of penetrating the entire body and causes ionization. The body can tolerate a certain amount of this, but that's why we use X-rays - they go through just about anything but bone/minerals and metals.

Airport security scanners emit terahertz radiation, which has a wavelength between microwave and infrared. This is a very low level of energy per photon. Terahertz radiation will not penetrate more than a centimeter of light material, which is more suitable to find hidden metal objects (which reflect terawaves). Relative to X-rays it causes practically no radiation damage. The intensity of the radiation is also pretty low since these scans are also detected by digital cameras, which are quite sensitive.

Compare the machinery. X-ray technicians, who might have to take dozens of X-ray exposures a day, usually go behind a protective screen to take a medical x-ray. The airport body scanners are open to the air and the terahertz radiation spills out into the crowd and the workers stand by it every day. It has practically no expectation of being hazardous. This device is pretty good as frequent fliers can have as many scans per year as are needed and health concerns are not significant.

Its always possible we might find some issues with Terahertz radiation in the future, but its hard to imagine it - its safer than standing 2 feet away from a working, closed oven.

As per the American Association of Physicists in Medicine the radiation exposure from full body airport scanners is equivalent to what an individual receives every 1.8 minutes on the ground from natural background radiation or equivalent to every 12 seconds during an airplane flight.

The Back scatter full body scanners at airports use X-rays.


Tomography is imaging by sections or sectioning through the use of any kind of penetrating wave. The method is used in radiology, archaeology, biology, atmospheric science, geophysics, oceanography, plasma physics, materials science, astrophysics, quantum information, and other areas of science. The word tomography is derived from Ancient Greek τόμος tomos, "slice, section" and γράφω graphō, "to write" or, in this context as well, " to describe." A device used in tomography is called a tomograph, while the image produced is a tomogram.

In many cases, the production of these images is based on the mathematical procedure tomographic reconstruction, such as X-ray computed tomography technically being produced from multiple projectional radiographs. Many different reconstruction algorithms exist. Most algorithms fall into one of two categories: filtered back projection (FBP) and iterative reconstruction (IR). These procedures give inexact results: they represent a compromise between accuracy and computation time required. FBP demands fewer computational resources, while IR generally produces fewer artifacts (errors in the reconstruction) at a higher computing cost. [1]

Although MRI and ultrasound are transmission methods, they typically do not require movement of the transmitter to acquire data from different directions. In MRI, both projections and higher spatial harmonics are sampled by applying spatially-varying magnetic fields no moving parts are necessary to generate an image. On the other hand, since ultrasound uses time-of-flight to spatially encode the received signal, it is not strictly a tomographic method and does not require multiple acquisitions at all.

Full-Body CT Scans - What You Need to Know

Using a technology that "takes a look" at people's insides and promises early warnings of cancer, cardiac disease, and other abnormalities, clinics and medical imaging facilities nationwide are touting a new service for health-conscious people: "Whole-body CT screening." This typically involves scanning the body from the chin to below the hips with a form of X-ray imaging that produces cross-sectional images.

The technology used is called "X-ray computed tomography" (CT), sometimes referred to as "computerized axial tomography" (CAT). A number of different types of X-ray CT systems are being promoted for various types of screening. For example, "multi-slice" CT (MSCT) and "electron beam" CT (EBCT) - also called "electron beam tomography" (EBT) - are X-ray CT systems that produce images rapidly and are often promoted for screening the buildup of calcium in arteries of the heart.

CT, MSCT and EBCT all use X-rays to produce images representing "slices" of the body - like the slices of a loaf of bread. Each image slice corresponds to a wafer-thin section which can be viewed to reveal body structures in great detail.

CT is recognized as an invaluable medical tool for the diagnosis of disease, trauma, or abnormality in patients with signs or symptoms of disease. It's also used for planning, guiding, and monitoring therapy. What's new is that CT is being marketed as a preventive or proactive health care measure to healthy individuals who have no symptoms of disease.

No Proven Benefits for Healthy People

Taking preventive action, finding unsuspected disease, uncovering problems while they are treatable, these all sound great, almost too good to be true! In fact, at this time the Food and Drug Administration (FDA) knows of no scientific evidence demonstrating that whole-body scanning of individuals without symptoms provides more benefit than harm to people being screened. The FDA is responsible for assuring the safety and effectiveness of such medical devices, and it prohibits manufacturers of CT systems to promote their use for whole-body screening of asymptomatic people. The FDA, however, does not regulate practitioners and they may choose to use a device for any use they deem appropriate.

Compared to most other diagnostic X-ray procedures, CT scans result in relatively high radiation exposure. The risks associated with such exposure are greatly outweighed by the benefits of diagnostic and therapeutic CT. However, for whole-body CT screening of asymptomatic people, the benefits are questionable:

  • Can it effectively differentiate between healthy people and those who have a hidden disease?
  • Do suspicious findings lead to additional invasive testing or treatments that produce additional risk with little benefit?
  • Does a "normal" finding guarantee good health?

Many people don't realize that getting a whole body CT screening exam won't necessarily give them the "peace of mind" they are hoping for, or the information that would allow them to prevent a health problem. An abnormal finding, for example, may not be a serious one, and a normal finding may be inaccurate. CT scans, like other medical procedures, will miss some conditions, and "false" leads can prompt further, unnecessary testing.

Points to consider if you are thinking of having a whole-body screening:

  • Whole-body CT screening has not been demonstrated to meet generally accepted criteria for an effective screening procedure.
  • Medical professional societies have not endorsed whole-body CT scanning for individuals without symptoms.
  • CT screening of high-risk individuals for specific diseases such as lung cancer or colon cancer is currently being studied.
  • The radiation from a CT scan may be associated with a very small increase in the possibility of developing cancer later in a person's life.
  • The FDA provides additional information regarding whole-body CT screening on its Computed Tomography (CT) Web site.

FDA's Recommendation:

Before having a CT screening procedure, carefully investigate and consider the potential risks and benefits and discuss them with your physician.

You vs. TSA: How to Choose Between Body Scanners and Pat-Downs

Sarah Pascarella has a master's degree in writing, literature, and publishing from Emerson College, where she specialized in magazine writing and nonprofit publishing. She is a member of the North American Travel Journalists Association and the New England Writers association.

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To go through the security scanner or get a pat-down? Many travelers grapple with this question each time they go to the airport. I know many of you are skittish about the body scanners found at airports around the world, yet the alternative of pat-downs also may hold little appeal.

How do you determine which option works better for you? Unfortunately, there are no hard and fast rules, says Chris Calabrese, legislative counsel, ACLU: &ldquoIf you can&rsquot bear the thought of someone seeing a naked photo of you, avoid the scanner. If you don&rsquot want to be touched, the scanner is a better option over a pat-down. It&rsquos a choice between two not-great options, and each person will have to decide which is better based on their own preferences.&rdquo

Radiation, DXA Scans, and You

Concerns about radiation are some of the most frequent questions we get from prospective clients looking to do a BodySpec DXA scan.

When we think about radiation, we tend to think of explosions or nuclear meltdowns. But actually, radiation is all around us, and our bodies safely absorb small amounts of natural radiation on a daily basis.

Not all radiation is of the same type, so scientists use the unit “sievert” to measure the health risks of radiation. One sievert of radiation causes immediate sickness. But one sievert is a pretty massive dose of radiation, and most radiation doses are much, much smaller.

1 sievert (Sv) = 1000 millisieverts (mSv) = 1,000,000 microsieverts (uSv)

And it turns out that in the grand scheme of things, getting a BodySpec DXA scan is very safe, even if you scan multiple times a year (or within the same day). In fact, getting a DXA scan gives you about the same amount of radiation as eating 4 bananas.

See below for a comparative chart of radiation exposure levels from different everyday (and not so everyday) sources.

Radiation Exposure Source
0.05 uSv Sleeping next to someone
0.1 uSv Eating one banana. Bananas are slightly radioactive because of their potassium. Many foods contain trace radioactive elements occurring naturally
0.25 uSv Airport security screening
0.4 uSv BodySpec full body composition DXA scan
1 uSv Using a CRT computer or TV monitor for a year
10 uSv Background radiation received by an average person over a normal day. This comes from cosmic rays, the Earth’s crust and soils, buildings, food, and medical scans
40 uSv Round trip flight from New York to LA
70 uSv Living in a stone, brick, or concrete building for a year
400 uSv Mammogram
1.5-1.7 mSv
(1,500 - 1,700 uSv)
Average annual dose for flight attendants
2 mSv
(2,000 uSv)
A head CT scan
5-6 mSv
(5,000 – 6,000 uSv)
A chest CT scan
13 mSv
(13,000 uSv)
Smoking 1.5 packs of cigarettes daily for a year
50 mSv
(50,000 uSv)
Annual dose limit for nuclear power plant workers
200 mSv
(200,000 uSv)
Average dose of survivors within 2.5 km of the Hiroshima and Nagasaki atom bombs. Out of 50,000 survivors, about 850 died from leukemia or cancers directly attributable to radiation
1 Sv
(1,000,000 uSv)
Measured in water leaking from Fukushima No. 2 reactor over one hour. Direct exposure at this level causes symptoms such as nausea and decreased white blood cell count, but not immediate death. However, exposure at this level is correlated with increased risk of future death from cancer
6 Sv
(6,000,000 uSv)
Typical for Chernobyl workers who died within a month.

Anyone receiving a dose of over 5 sieverts has only a 50% chance of survival

How Millimeter Wave Scanners Work

On Christmas Day in 2009, Umar Farouk Abdulmutallab tried to detonate explosives in his underwear on a flight from Amsterdam to Detroit. Like all other post-9/11 terrorist acts involving airplanes, Abdulmutallab's failed attempt led to new passenger screening techniques and technologies.

By December 2010, the Transportation Security Administration (TSA) had introduced 500 whole-body scanners -- what the U.S. government agency refers to as advanced imaging technology units -- at airports across the country. All of the scanners do the same thing: detect metallic and nonmetallic threats, including weapons, explosives and other objects, concealed under layers of clothing. But they use completely different technologies.

One type of scanner relies on something known as backscatter technology. Backscatter machines use a device called a collimator to produce a parallel stream of low-energy X-rays, which pass through a slit and strike a passenger standing in the machine. A single scanner includes two radiation sources so that both the front and the back of the person can be imaged. The images form when X-rays, which penetrate clothing, bounce off the person's skin and return to detectors mounted on the machine's surface. The radiation also bounces off weapons, explosives or other threats concealed in clothing or lying against the skin.

The other type of scanner uses a competing technology known as millimeter wave (mmw) imaging. These machines work on the same principles, except they emit a special type of microwave, not X-ray. Two rotating transmitters produce the waves as a passenger stands still inside the machine. The energy passes through clothing, bounces off the person's skin -- as well as any potential threats -- and then returns to two receivers, which send images, front and back, to an operator station.

Unfortunately, what was supposed to ease the public's worries has only caused agitation and anxiety -- among passengers, pilots and TSA agents. Many people have voiced concerns about the health risks of the scanning process for both technologies. How much radiation do these machines produce? How does it compare to medical imaging devices? And is it enough to increase cancer rates in the general population? Then there are the questions about privacy. Can TSA agents see bits and pieces they shouldn't be seeing? And do they ever store or archive scans instead of deleting them immediately?

The rush to answer these questions has spawned a number of myths and misconceptions. It's almost as if whole-body scanners, machines capable of peering deep into our soul (or at least beneath our clothes), are themselves opaque. In reality, they're not. They take advantage of well-understood scientific principles that have been around for years. Let's throw back the curtain on millimeter wave scanners to understand how they work and how they're used at airports around the world.

How Contrast Dye Works

Contrast can be swallowed as a drink or injected into a vein. The kind of exam you are receiving will determine what kind of contrast you’ll need. It will also determine how it needs to be administered (orally or intravenously). Your body will naturally absorb or eliminate the contrast materials after your exam.

Contrast dye works by using substances that interfere with how the medical imaging equipment takes your images. For example, the contrast used in an X-ray or CT exam is made of a substance that will block or limit radiation in certain parts of your body. This changes how the tissues that contain the medical imaging contrast appear on your images.

Similarly, contrasts used in magnetic-powered exams like MRIs and ultrasounds alter the way magnetic fields interact with the parts of the body containing contrast. So, contrast doesn’t alter anything inside of you, it only alters the way medical imaging equipment sees the inside of you.

If you need contrast, your exam will probably take longer than if you weren’t having contrast. For example, it could add four hours of prep time to a five-minute CT scan or make a thirty-minute MRI last two hours. This is because of the time it takes to administer the contrast and for it to start working. Although it takes longer, the clearer images it provides for your doctor are worth the wait.

Are Full Body Airport Scanners Harmful?

Many experts raise questions about personal privacy being invaded because of the detailed imaging that comes from a full body scan, while others are more concerned about the potential for damage to a person’s health because of X-ray (radiation) exposure. The United States Transportation Security Administration addressed the question of additional X-ray exposure and stated that the machines emit doses similar to what a person would experience in two minutes of flying on an airplane.

In the past, full body scanning was only used as a last resort when all other diagnostic tools had failed in finding tumors in a person that had cancer. During the early 2000’s, more than 32 million individuals had their body’s X-rayed using a full body imaging machine. Since that time numbers have dwindled, possibly due to the fact that medical professionals warned that too many scans could actually be harmful instead of beneficial.

Undergoing scan rises the chances of dying from radiation-related cancer

A team of scientific researchers at Columbia University reported in a Radiology journal precise levels of radiation a person is exposed to when undergoing a full body scan. The levels are actually startling researchers found that the levels of radiation in a full body scan are equal to that received by a Hiroshima survivor living within a ½ mile of the atomic bomb explosion. While the risks associated with one scan are moderate, each time a person undergoes another scan the chances of dying from radiation-related cancer rise 0.8%.

Other experts have found that the radiation levels from one scan alone can be enough to produce a cancer tumor in one of every 1,200 people. For people that have an annual scan or frequent flyers that undergo routine full body airport scanning, the levels of radiation exposure can be very dangerous and risky. When used for diagnostic purposes, a full body scan is undeniably beneficial, but when used for airport security reasons, the line becomes blurred by controversy. Furthermore, the American Cancer Society, the Environmental Protection Agency, the Food and Drug Administration and the American College of Radiology strongly advise against using full body scanning for reasons other than medical purposes.


When used for diagnostic reasons, a full body scan can be a life saving option for many people. However, the question still remains, are full body airport scanners harmful to humans? Medical professionals and research experts are divided and further studies are needed in order to determine a better understanding of just how harmful routine body scanning can be in humans. Because use of the machines is fairly new and there has not been enough time, researchers are not able to make a definitive determination of just how full body scans directly relate to an increased risk of cancer and tumors in people and but will be able to do so at some point in the future.


Cross-section ultrasound image of a fetus Source: Phillips Health Care- iu22xMATRIX system

Medical ultrasound falls into two distinct categories: diagnostic and therapeutic.

Diagnostic ultrasound can be further sub-divided into anatomical and functional ultrasound. Anatomical ultrasound produces images of internal organs or other structures. Functional ultrasound combines information such as the movement and velocity of tissue or blood, softness or hardness of tissue, and other physical characteristics, with anatomical images to create “information maps.” These maps help doctors visualize changes/differences in function within a structure or organ.

Therapeutic ultrasound also uses sound waves above the range of human hearing but does not produce images. Its purpose is to interact with tissues in the body such that they are either modified or destroyed. Among the modifications possible are: moving or pushing tissue, heating tissue, dissolving blood clots, or delivering drugs to specific locations in the body. These destructive, or ablative, functions are made possible by use of very high-intensity beams that can destroy diseased or abnormal tissues such as tumors. The advantage of using ultrasound therapies is that, in most cases, they are non-invasive. No incisions or cuts need to be made to the skin, leaving no wounds or scars.

Source: Terese Winslow

Ultrasound waves are produced by a transducer, which can both emit ultrasound waves, as well as detect the ultrasound echoes reflected back. In most cases, the active elements in ultrasound transducers are made of special ceramic crystal materials called piezoelectrics. These materials are able to produce sound waves when an electric field is applied to them, but can also work in reverse, producing an electric field when a sound wave hits them. When used in an ultrasound scanner, the transducer sends out a beam of sound waves into the body. The sound waves are reflected back to the transducer by boundaries between tissues in the path of the beam (e.g. the boundary between fluid and soft tissue or tissue and bone). When these echoes hit the transducer, they generate electrical signals that are sent to the ultrasound scanner. Using the speed of sound and the time of each echo’s return, the scanner calculates the distance from the transducer to the tissue boundary. These distances are then used to generate two-dimensional images of tissues and organs.

An ultrasound transducer.

During an ultrasound exam, the technician will apply a gel to the skin. This keeps air pockets from forming between the transducer and the skin, which can block ultrasound waves from passing into the body.

Diagnostic ultrasound. Diagnostic ultrasound is able to non-invasively image internal organs within the body. However, it is not good for imaging bones or any tissues that contain air, like the lungs. Under some conditions, ultrasound can image bones (such as in a fetus or in small babies) or the lungs and lining around the lungs, when they are filled or partially filled with fluid. One of the most common uses of ultrasound is during pregnancy, to monitor the growth and development of the fetus, but there are many other uses, including imaging the heart, blood vessels, eyes, thyroid, brain, breast, abdominal organs, skin, and muscles. Ultrasound images are displayed in either 2D, 3D, or 4D (which is 3D in motion).

The ultrasound probe (transducer) is placed over the carotid artery (top). A color ultrasound image (bottom, left) shows blood flow (the red color in the image) in the carotid artery. Waveform image (bottom right) shows the sound of flowing blood in the carotid artery.

Functional ultrasound. Functional ultrasound applications include Doppler and color Doppler ultrasound for measuring and visualizing blood flow in vessels within the body or in the heart. It can also measure the speed of the blood flow and direction of movement. This is done using color-coded maps called color Doppler imaging. Doppler ultrasound is commonly used to determine whether plaque build-up inside the carotid arteries is blocking blood flow to the brain.

Another functional form of ultrasound is elastography, a method for measuring and displaying the relative stiffness of tissues, which can be used to differentiate tumors from healthy tissue. This information can be displayed as either color-coded maps of the relative stiffness black-and white maps that display high-contrast images of tumors compared with anatomical images or color-coded maps that are overlayed on the anatomical image. Elastography can be used to test for liver fibrosis, a condition in which excessive scar tissue builds up in the liver due to inflammation.

Ultrasound is also an important method for imaging interventions in the body. For example, ultrasound-guided needle biopsy helps physicians see the position of a needle while it is being guided to a selected target, such as a mass or a tumor in the breast. Also, ultrasound is used for real-time imaging of the location of the tip of a catheter as it is inserted in a blood vessel and guided along the length of the vessel. It can also be used for minimally invasive surgery to guide the surgeon with real-time images of the inside of the body.

Therapeutic or interventional ultrasound. Therapeutic ultrasound produces high levels of acoustic output that can be focused on specific targets for the purpose of heating, ablating, or breaking up tissue. One type of therapeutic ultrasound uses high-intensity beams of sound that are highly targeted, and is called High Intensity Focused Ultrasound (HIFU). HIFU is being investigated as a method for modifying or destroying diseased or abnormal tissues inside the body (e.g. tumors) without having to open or tear the skin or cause damage to the surrounding tissue. Either ultrasound or MRI is used to identify and target the tissue to be treated, guide and control the treatment in real time, and confirm the effectiveness of the treatment. HIFU is currently FDA approved for the treatment of uterine fibroids, to alleviate pain from bone metastases, and most recently for the ablation of prostate tissue. HIFU is also being investigated as a way to close wounds and stop bleeding, to break up clots in blood vessels, and to temporarily open the blood brain barrier so that medications can pass through.

Diagnostic ultrasound is generally regarded as safe and does not produce ionizing radiation like that produced by x-rays. Still, ultrasound is capable of producing some biological effects in the body under specific settings and conditions. For this reason, the FDA requires that diagnostic ultrasound devices operate within acceptable limits. The FDA, as well as many professional societies, discourage the casual use of ultrasound (e.g. for keepsake videos) and recommend that it be used only when there is a true medical need.

The following are examples of current research projects funded by NIBIB that are developing new applications of ultrasound that are already in use or that will be in use in the future:

Acoustic Radiation Force Impulse Imaging (ARFI). ARFI is a new technique developed by researchers at Duke University with NIBIB support that uses ultrasound elastography to differentiate liver tumors from healthy tissue, as well as identify the presence of fibrosis. This non-invasive method could reduce unnecessary liver biopsies, which can be painful and sometimes dangerous. ARFI has received FDA approval and is now commercially available in the U.S. (Image on left courtesy of Katharine Nightengale, Ph.D., Duke Biomedical Engineering).

Low-cost, miniature ultrasound. Just like computers, medical ultrasound imagers have been getting smaller and smaller. One of the biggest challenges is connecting the ultrasound transducer at the tip of the probe to the extensive computer chip-based signal processing and imaging electronics. NIBIB funding was important in demonstrating this level of extreme miniaturization — in effect, a “system inside the probe.”

This “system inside a probe” imaging paradigm was subsequently extended into the GE Vscan device. The Vscan is a palm-size ultrasound scanner, which has both anatomical imaging and color Doppler capability. The device is currently in clinical use and costs considerably less than a full-sized ultrasound scanner. Its small size and low cost, as well as range of applications, allow it to be used in ambulances, emergency rooms, field hospitals, or other remote locations. It is currently being used in more than 60 countries around the world. (Vscan image on right courtesy of Kai Thomenius, Ph.D., GE).

Ultrasound color Doppler shows a clot blocking blood flow in a pig. Source: Zhen Xu, Ph.D., Univ. of Michigan After 5-minute histotripsy treatment the clot is gone and full blood flow is restored in the blood vessel. Source: Zhehn Xu, Ph.D., Univ. of Michigan

Histotripsy technique for dissolving blood clots. Researchers at the University of Michigan are investigating the clot-dissolving capabilities of a high intensity ultrasound technique, called histotripsy, for the non-invasive treatment of deep-vein thrombosis (DVT). This technique uses short, high-intensity pulses of ultrasound to cause clot breakdown. The researchers have successfully demonstrated the effectiveness of this technique in pigs and its possible use in humans. They are currently working on new methods to avoid inadvertent vessel damage during clot treatment, and to provide real-time imaging feedback to monitor the treatment. This research could have a significant impact, since current conventional treatments for DVT involve drug therapy and sometimes invasive removal of the clots, which requires a several-day hospital stay, and may result in complications after treatment. In contrast, the non-invasive histotripsy technique is 50 times faster than the current technique, does not require drugs or external agents, and if successful, could be used as an outpatient procedure.

New passenger scanner uses space technology to speed up airport security

Credit: Cardiff University

A super-sensitive passenger scanner that reveals hidden security threats is being trialled at Cardiff Airport in the UK.

The walk-through scanner, which uses space technology to image human body heat, is the result of a collaboration between Sequestim Ltd. and Cardiff University scientists.

Computer learning allows the scanner to distinguish between threats and non-threats but without the need for passengers to keep still or remove outer clothing.

Globally, around 12 million passengers travel by plane every day on 120,000 flights.

The technology has the potential to cut queues at airport terminals as it screens people on the move. It will also impact on the effectiveness of security and help keep passengers safe.

"Passenger numbers are expected to double in 20 years, putting airport security facilities under immense pressure," said Ken Wood, Sales and Marketing Director of Sequestim Ltd, a joint venture between Cardiff University and QMC Instruments Ltd.

"Our scanner combines a number of world-leading technologies developed by our team here in the UK. It uses the human body as a source of "light", in contrast with existing scanners which process reflected and scattered millimetre-waves while the passenger is required to strike a pose."

"Our system only needs a few seconds to do its work. Passengers walking normally through security would no longer need to take off coats and jackets, or remove personal items such as phones."

The trial takes place privately, by invitation only, from 4 to 7 December 2018 and will not affect passenger journeys.

The project is one of eight to receive some of the £1.8m funding made available by the UK Government earlier this year through a Defence and Security Accelerator themed competition. Part of the five year Future Aviation Security Solutions (FASS) programme, the multimillion-pound initiative seeks innovative ideas such as this new passenger scanner to help strengthen aviation security.

Originally built to study the furthest reaches of the universe, the technology used is so sensitive it could see a 100W light bulb at a distance of 500,000 miles (twice the distance to the Moon.)

The scanner quickly "learns" the difference between items that can and cannot be taken onto an aircraft, reducing the risk of false alarms which inconvenience passengers and slow down screening.

"The detector technology was originally developed to study the most distant astronomical phenomena. For example, we study how stars are born from gigantic clouds of gas and dust," explained Mr Wood.

Credit: Cardiff University

"It detects millimetre-waves, which are just like visible light but at a wavelength more than one thousand times longer. The ability of the scanner to reveal hidden objects has also attracted interest from Border Force, responsible for the UK's frontline border control operations at air, sea and rail ports.

The airport trial aims to prove that passive terahertz imaging is robust, versatile, fast and convenient.

UK Aviation Minister Liz Sugg said: "We have a proud history of innovation here in the UK and passenger safety across all modes of transport remains an important priority for the government. The Future Aviation Security Solutions programme demonstrates our support for pioneering projects that can help to reduce security threats in airports. I am pleased to see that the funding awarded to Sequestim has helped the team take space technology and trial it as part of a new passenger screening system at Cardiff Airport."

Cardiff Airport was bought by Welsh Government for £52m in 2013. Nearly 1.5m passengers passed through the airport in 2017. The trial of the passenger scanner in December represents a first for Wales, and a local collaboration with enormous impact potential.

First Minister of Wales, Carwyn Jones, said: "Welsh Government and Cardiff Airport are delighted to be hosting the proof-of-concept trial of Sequestim's innovative technology. This cutting-edge security camera not only promises a huge improvement in our experience of air travel, but also brings with it the prospect of job creation as Sequestim aims to manufacture future scanners here in Wales."

The purpose of the trial is for key members of industry, the Centre for the Protection of National Infrastructure, the Civil Aviation Authority and other government bodies including BorderForce to see the technology in action.

The Electromagnetic Spectrum: Non-Ionizing Radiation

Radiation exists all around us, from both natural and manmade sources, and is in two forms: ionizing and non-ionizing radiation.

Ionizing radiation is a form of energy that acts by removing electrons from atoms and molecules of materials that include air, water, and living tissue. Ionizing radiation can travel unseen and pass through these materials.

What is non-ionizing radiation?

Non-ionizing radiation exists all around us from many sources. It is to the left of ionizing radiation on the electromagnetic spectrum in the figure below.

  • Radiofrequency (RF) radiation used in many broadcast and communications applications
  • Microwaves used in the home kitchen
  • Infrared radiation used in heat lamps

The dividing line between ionizing and non-ionizing radiation occurs in the ultraviolet part of the electromagnetic spectrum [shown in the illustration of the electromagnetic spectrum above]. Radiation in the ultraviolet band and at lower energies (to the left of ultraviolet) is called non-ionizing radiation, while at the higher energies to the right of the ultraviolet band is called ionizing radiation.

As we move to the left of the visible light band in the figure above, we move to lower frequencies. By &ldquofrequency&rdquo we mean how rapidly these waves move up and down. The lower the frequency, the lower the energy.

In these lower frequencies on the left side of the electromagnetic spectrum, we find infrared, microwave, radiowaves, and cell phone range radiation.

Put simply, non-ionizing radiation differs from ionizing radiation in the way it acts on materials like air, water, and living tissue

Unlike x-rays and other forms of ionizing radiation, non-ionizing radiation does not have enough energy to remove electrons from atoms and molecules. Non-ionizing radiation can heat substances. For example, the microwave radiation inside a microwave oven heats water and food rapidly.

We are exposed to low levels of non-ionizing radiation every day. Exposure to intense, direct amounts of non-ionizing radiation may result in damage to tissue due to heat. This is not common and mainly of concern in the workplace for those who work on large sources of non-ionizing radiation devices and instruments.

Risk from ultraviolet (UV) radiation exposure

Ultraviolet (UV) radiation is a natural part of solar radiation, and is released by black lights, tanning beds, and electric arc lighting. Normal everyday levels of UV radiation can be helpful, and produce vitamin D. The World Health Organization (WHO) recommends 5 to 15 minutes of sun exposure 2 to 3 times a week to get enough vitamin D.

Too much UV radiation can cause skin burns, premature aging of the skin, eye damage, and skin cancer. The majority of skin cancers are caused by exposure to ultraviolet radiation.

Tanning through the use of tanning beds and tanning devices exposes the consumer to UV radiation. Exposure to tanning beds and tanning devices also increases the chance of developing skin cancer.

Risk from exposure to radiofrequency (RF) and microwave radiation

Intense, direct exposure to radiofrequency (RF) or microwave radiation may result in damage to tissue due to heat. These more significant exposures could occur from industrial devices in the workplace.