John Howell, IED/EOD Security Specialist at 3DX-Ray, looks at why scanning vehicles from the top down makes more sense and why the ThreatScan® is the perfect tool for the job!

Vehicle borne improvised explosive devices (VBIEDs) present a significant risk and are very challenging to mitigate against. They require specialised equipment to inspect the vehicle, and flat panel portable x-ray systems are one of the best tools at our disposal.

Most people when x-raying a car will set up their generator on one side of the vehicle and their detector panel on the other.

The main reason that people do this is because historically portable x-ray equipment utilised low resolution (Golden) pulsed generators. The configuration of the Golden generator does not lend itself to standing it up on one end and shooting down into a car. And this has set a pattern of behaviour that is very hard to break.

The real problem with shooting from side to side is the further apart your generator and your panel, the worse your image gets.

That’s why taking side to side scans, often requires operators taking three or four sets of 99 pulses, but still ending up with a very poor image.

The distance between the panel and the generator is key.

It is a simple matter of physics, the further apart your panel and generator, the more disperse your photons, the less energy you have reaching your panel, the worse your image is.

So, why is a top-down scan a better option?

A typical car is approximately two meters wide. Add the distance required for the equipment set up, and you could be talking about two and a half meters distance between your generator and your panel.

Measuring the same vehicle from top to bottom, and you’re looking at a distance of no more than one, to one and a half meters.

Dramatically reducing the distance between your panel and generator is the single most important factor, but it’s not the only one.

There are of course other things to take into consideration. In a side-to-side scan, not only can the metal be thicker on the vehicle side panels, but there may also be framing sections within the trunk meaning overlapping layers of metal in your image.

For a top-down shot there are typically only two layers of metal, the trunk lid and the bottom of the vehicle. These tend to be made of thinner metal, perhaps as thin as one millimetre.

Then of course there may be multiple items in the trunk.

Typically, these items are likely to be closely packed together creating multiple layers at multiple angles, which is the worst scenario when trying to obtain a clear image of what’s inside the trunk.

As you can see in the image above, we are able to image the entire sidewall of the car. The top down approach provides a very high-quality image and can easily penetrate the metal of the car. Highlighted in red is the PVC pipe bomb (low density vs the metal exterior).

Here is another example of a Top-Down attack that lets you see a PVC pipe bomb and handgun that is hidden in the spare tire compartment. You can see that the system also was able to see right through the car muffler.

However, when you shoot straight down the items are usually at a straight angle and they are not all lined up, so increasing your ability to see what’s going on within the trunk.

So, let’s look at some likely scenarios where an IED is hidden in a vehicle.

The most obvious one is when the device is hidden within the cavity created for the spare tyre.

A suspect item is in the car seat and we again use the top-down x-ray technique to image the item.

IED In Dashboard Glove Box.

From the side your scanner will not only have to contend with greater distance but will have to penetrate six layers of metal in addition to the wheel rims if the spare tyre is still in place.

From the top you are only likely to encounter three layers at most. Another scenario is a package on the back seat or passenger seat, and you are unable or are unwilling to gain entry, you will need to scan.

From the side not only will you have to contend with the greater distance, but the doors have multiple layers of metal for strengthening, as well as electronic components, making it instantly, a much more challenging imaging problem.

This is a image of a car tire that has a IED hidden inside of it. We were able to image the IED and even used the probe feature to identify the organic explosive material.

Again, a top-down scan means shorter distance and less layers, and with a an under vehicle trolley it means the locating of the flat panel scanner is easily achieved.

Another scenario is when a potential IED is hidden within a door panel.

From a side scan it can be very difficult to identify which door the device is hidden within.

By taking an angled scan of a door from above, not only do you get a better image, but you also identify the exact location of the device.

The beauty of using a system like our I-Gen generator is that with its 360 degrees of rotation on an adjustable stand and rubber feet, the operator is able to place the I-Gen anywhere on top of the vehicle and change the angle of the scan.

This means that it is possible to scan virtually anywhere in the car, including under the seats, the centre consul, glove box, wings and areas of the engine bay, without actually having to access the vehicle, which is clearly a major safety concern in a VBIED scenario.

Under vehicle trolley for LS1 Detector Panel.
LS1 Panel provides 60 x 46 cm imaging area that is equivalent to two 35 x 43 panels.

There are other technologies that have been widely used up to this point, which have included a series of CR plates to scan large areas, typically a combination of six (14” x 17”) plates at a time on the side of a vehicle. This technique has a number of disadvantages in regards to the time it takes to acquire the image, but also because the area which the x-ray beam is illuminating is very large, which will mean reduced penetration. It is much more effective to take a top-down approach with a scanning panel that allows the acquisition of material discrimination images, where the system can highlight the varying material types and assist an operator in identifying contraband or parts of an IED.

Flat panel x-ray scanner systems like the ThreatScan® are a light, flexible and powerful tool that can be used in a wide range of scenarios, offering operators high-quality real-time x-ray images, enabling quick, safe decision making, so important in potential terrorist situations.

With these systems, the right training and the right techniques, side to side scans simply no longer make sense. ■


John Howell professional career: 12 years U.S. Marines Explosive Ordnance Disposal Technician and disabled combat veteran. 8 years U.S. Department of State Diplomatic Security Service Explosive Countermeasures Unit and Explosive Detection Program. 7 years U.S. Marshals Training and Compliance Branch for Court Security Officer Training at the Federal Law Enforcement Training Center. 4 years U.S. Army National Guard Explosive Ordnance Disposal Technician Training NCOIC and Team Leader certified. 8 years Director of Explosive Technologies DSA Detection. Currently Director of Counter IED Training and Technologies SVS Countermeasures Training, Director of Counter IED Technologies International Bomb Disposal and Counter IED Organization, IED/EOD Security Specialist 3DX-RAY for all of North America operations.

Contact: Tel.: +1 828 564 3456,

Download PDF: 75-79 John Howell of 3DX-Ray article – C-IED REPORT, SS 2021