Kirstine Wilson Reviews X-ray Technology and it's Applications

The invention of the x-ray by Roentgen in 1895 created an amazing step forward in the history of medicine. Today we see X-ray technology used in many different fields as a non-invasive inspection tool and not least in the field of security where x-rays are used for baggage scanning at airports, mailscanning in postrooms, vehicle scanning at border controls and more recently through body x-ray scanners for identifying contraband, weapons and IEDs concealed on a person. For field use, specially adapted portable systems have been developed to meet the different investigative needs of military theatres and national military and civil search.

X-ray technology today uses the same basic principles in that x-rays are passed through an object and a latent shadow image is captured on an imaging panel placed behind it. Different materials will absorb different numbers of photons so that the relative densities of the object can be seen as differences in grey scales when viewed on a screen.
Pre 9/11 many field based x-ray systems were still operating manual Polaroid film technology where an x-ray source was placed in front of the object requiring scanning and a cassette placed behind. The x-ray generator was manually fired by the operator and then the target area would be reapproached for the film to be retrieved for chemical processing.

Although the resulting image was fairly good, it could be quite a time consuming process as the processing itself could take up to 2 minutes and if the development was not carried out in the correct conditions, several attempts were often needed before getting a picture of sufficiently good resolution. Each attempt meant another sheet of Polaroid film which involve significant weight and cost factors when carrying out multiple x-rays of a large target.

In addition film had dead areas where edges of cassettes were joined or unexposed and where potentially an IED could go unseen. If dead areas are found additional x-rays need to be taken which increases time on target for EOD personnel.

The range of portable x-ray equipment available in the security market is growing. Conventional Polaroid film systems are gradually being replaced by “real time” systems where images are displayed in digital form on a laptop or other portable device.

Fundamentally there are 2 primary technologies available off the shelf to upgrade older Polaroid film systems to a digital platform whilst operating the same safe, tried and tested x-ray generators.

The first is DR – Direct (Digital) Radiography which use either a rugged CCD X-ray Imager or a very high resolution amorphous silicon (aSi) flat panel imager to capture x-ray images before sending them directly back to a laptop and the second is known as CR – Computed Radiography which utilises very flexible reusable digital film and an image plate processor that scans the x-ray image onto the laptop via a USB data connection.

Each has its own benefits dependent on the requirements of the job but all of the imaging panels described in this article are lightweight and can be handled easily even by someone wearing heavy body armour.

If we look first at the picture in overseas theatres such as Iraq and Afghanistan, their needs will be quite different from the requirements of a postal inspector needing to check a suspect package or a special projects team carrying out a room search.

The homemade IED is the extremist’s deadliest weapon and our troops' biggest challenge. In 2003 there were 81 recorded IEDs in Afghanistan. In 2009 there were over 8,000. Half of all soldiers killed in Iraq were killed by IEDs and currently in Afghanistan it is two thirds.
Early detection (or better, prevention) of IEDs is mission critical which is why current Counter IED methodology is focused on Defeat the Device (finding the weapon and protecting against its effects) Attack the Network (identify what an IED cell looks like so that the networks can be identified and attacked) and Train the Force.

Detection of IEDS is a daunting challenge. IEDS are being concealed in everyday items such as drinks cans, toy cars, key rings and mobile phones and can be very easily disguised in rubbish, potholes and craters and a high percentage are frequently spotted by soldiers noticing something doesn’t look right. In this instance x-ray equipment may be deployed as a confirmatory tool or to remotely diagnose the insides of an object without picking it up.

In such instances where the equipment is going to be used regularly by someone often operating on foot, for Special Forces a highly portable lightweight system that can be carried in a backpack would be the key requirement. A CCD imaging system also represents a very cost effective solution.

A real time CCD x-ray system is combination of camera and x-ray source at the target and laptop or other viewing console at the control point. CCD systems produce a latent x-ray image on photoluminescent screen. A camera sends the image back to the laptop directly down a cable or by wireless transmission and multiple exposures can be made to gain the best possible image without having to return to the target.

The most compact and portable solution on the market and one which represents some of the latest improvements in cameras and processing is the Scanwedge system which has a unique flat panel CCD X-ray imager The entire system weighs less than 10kgs in a backpack comprises only 3 components (x-ray generator, image panel and a small handheld tablet pc), x-ray investigation of an item can be carried out quickly and rapidly in even the most difficult to access areas. Unlike other CCD systems it does not use a mirror and is extremely rugged and flat.

Many CCD systems, including Scanwedge, can be fully integrated onto EOD robots allowing the EOD team to move the x-ray equipment into place as well as controlling the x-ray system over the robot communications link or over wireless communication where applicable.

In order to attack the IED network, our military teams need detailed information on the construction and composition of IEDs. Following discovery or activation of an IED every fragment is essential to the forensic team to understand both its makeup and its likely provenance. These teams gather evidence from blasts and each device is reconstructed, replicated and tested.

X-ray investigation enables forensic teams to recognise a signature and also to identify patterns in bomb making that may identify a change in tactics or identify components from a common source. Recent investigation of wires, charges and other explosive components used in a series of bombs have indicated materials are being sourced from specific areas which means strategies to block these trade routes can be put into place.

Forensic procedures and post blast analysis associated with IEDs do not need to be carried out where the device is found. Therefore ruggedness and portability are less of an issue and image resolution becomes the determining factor.
Computed Radiography (CR) systems really come into their own for this type of task.

Modern computed radiography, using storage phosphor imaging plates, can be traced to 1973, when George Luckey, a research scientist at Eastman Kodak Company, filed a patent application titled Apparatus and Method for Producing Images Corresponding to Patterns of High Energy Radiation. His abstract states, “A temporary storage medium, such as an infrared-stimulable phosphor or thermoluminescent material, is exposed to an incident pattern of high energy radiation.

With phosphor imaging plates, you can shoot one image instead of the five or more you may need to shoot on film. That’s because a phosphor imaging plate has ten times the dynamic range of film.

Unlike DR systems where the x-ray image transmits directly to the laptop, CR imaging plates need to be manually retrieved and fed through an image plate processor before the image can be viewed. For post blast investigation this time factor is less of a concern.

In all types of EOD tasks, in theatre or otherwise there will be the requirement to identify the type of IED/UXO in question and discern the makeup and location of the component parts within the device in order to carry out a render safe procedure. For this application a CR system is also ideal.

Where an IED/EOD team has a vehicle, the resolution provided by a CR or aSi x-ray system is often of greater relevance than the cost, weight or rugged factor of a CCD system.

The real benefit of a CR system is that the imaging plates are extremely flat and flexible and can be taped onto any flat surface. In addition, multiple imaging plates can be taped together to x-ray a larger object in a single x-ray exposure. More importantly CR x-ray systems can produce extremely high resolution images with pixel sizes down to 50 microns and capable of seeing 10 line pairs which is critical for the forensic analysis and for render safe procedures.

In addition, Extra clarity makes detection much faster, easier and leads to a real reduction in false alarms
The national terrorist threat has evolved rapidly since the events of 9/11 and the emphasis on traditional targets such as military bases has shifted. Any public area, building or event where large numbers of people congregate is now considered a viable target.

More typically, IEDs are placed inside a building and secreted in places with relatively easy access including toilet facilities, reception areas, hallways and stairwells
The primary use of portable x-ray equipment in these scenarios is to help military, police or specialist forces examine inside suspect packages.

A suspect package could be a parcel left in a reception area, a suitcase left unattended at airport, a sports bag left by the side of the road or any object that is unexpected or looks out of place in its surroundings. Early identification of bags that do not represent a threat and eliminating those false alarms is essential.

The deployment of large numbers of military teams in Iraq and Afghanistan means that traditional EOD resources in some countries are vastly overstretched, so that the responsibility for the search and detection of suspicious bags and packages is often passed to the police and to individual premises managers.

Of the Quarter of a million suspect packages found on the railway system in the UK less than 1% will need attendance by bomb disposal squads, which again demonstrates the importance of x-ray screening by police and civil security teams.

Context, location and deployment all come into the equation when selecting the correct x-ray system for operation.
In the USA, Postal inspectors are trained to screen suspicious mail for IEDS. They are performing regular confirmatory actions and carry conventional realtime CCD based x-ray systems on their vehicles which mean they can usually resolve incidents without tying up valuable first responder resources.

For fast deployment on foot to perform a simple confirmation of a package or bag’s contents a lightweight CCD x-ray system is normally the most applicable.
For a vehicle, building and room search requiring more indepth information a CR system may be more suited to the job. The image plates used with CR x-ray system are able to flex around corners. They can be taped onto walls, or be placed in overhead plane luggage bays, for example, come in a range of sizes, and can be combined on a freestanding mount for checking large items such as suitcases. The dynamic range is such that even a tiny wire hidden inside a wall or ceiling cavity would be visible.

Unlike Polaroid film, digital x-ray plates have a 100% active area so a complete and accurate picture of the entire contents can be taken. and can be mounted in multiple configurations to cover a large area. Flexible plates can be wrapped around pipes or bent over an aircraft wing.

Image plates are scanned in individually and the software seamlessly stitches them together into a single large format image so that single large items such as a suitcase or a wall area can be checked in a single scan.

Where there is a risk of chemical, biological, radiological, or nuclear (CBRN) material being present in an IED additional precautions are required and in these instances an Amorphous Silicon or aSi flat panel system would be the most applicable tool for this job.

Large area aSi imaging systems have a dynamic range so high it allows penetration and details previously unavailable. Their high resolution 143 micron pixel size will capture the finest detail of wiring or circuitry with a fast readout times of 1 second. Such systems can be backpacked for lightscale operations.

To provide information on organics which are helpful to CBRNE responders, Asi panels can be used with Dual energy modules fitted onto a pulsed x-ray source. Dual energy allows x-rays to be measured in two different energies, which the x-ray separates into different colours to enable bomb responders to identify and differentiate organic and inorganic materials.

The image processing software used to control, view and manipulate digital x-ray images is just as important as the imaging panels them. Today’s powerful image visualization software lets you focus on suspect areas and draw out details. With fewer images to examine and the ability to adjust them, a more thorough analysis is possible.

Some x-ray systems are provided with imaging software proprietory to the imaging panel so that security teams operating more than 1 type of x-ray equipment often have to learn different software programs. Other software platforms such as Scanview from Scanna will operate across the entire range of x-ray imaging panels (CCD, CR and aSi) so that training requirements are greatly reduced.

Scanview software is so intuitive that you can quickly master it. The X-ray image is saved within an incident record. The image file encompasses other key information such a User Name, Date, Time, Place, Type of X-ray source used, KV, Exposure time, Description, etc. The image is saved in the System Database which can be queried and sorted for fast image retrieval using any of the parameters. As the images are digital files they are easily stored & transferred to colleagues by email, CD, memory stick or even across the internet.

The x-ray image data is used in a number of ways including the analysis of X-ray data for identification of explosives/initiators/booby traps, to produce technical reports on findings and develop device profiles and to maintain and document chain of custody of x-ray data.
It is clear that x-ray technology available today is a quantum leap from the very first x-ray Roentgen took over a century ago and that there are many considerations to make when selecting a system.

What is also clear that whatever the demands of the job, whether you need a lightweight system, a system with flexible plates, a high performance system with a wide dynamic range, a system that will operate off vehicle power or an x-ray product capable of dealing with CBRNE requirements, there are systems available off the shelf to meet those needs.

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