Understanding the Physics Behind X-Ray Baggage Screening

When X-rays pass through your luggage, they scatter off atoms in different materials. This results in varying amounts of slow-moving radiation (X-rays) that can be detected by an X-ray scanner.

The X-ray images produced by the machine show different materials as different colors. For example, orange represents organic materials, while green indicates inorganic items such as metals or explosives.

What is an X-ray?

An X-ray is a type of radiation that can pass through most objects, including your body. X-rays can help doctors and dentists see bones in your body and detect problems like broken bones or gum disease. They can also be used during procedures like coronary angioplasty to help guide a catheter (a thin, flexible tube) through one of your arteries.

X-rays are created by passing electrons through an atomic nucleus. These electrons scatter and interact with the nuclei of other atoms, producing X-rays. X-rays can penetrate materials depending on their thickness and the energy of the X-rays. High-energy, or hard, X-rays penetrate thicker objects more deeply than low-energy, or soft, X-rays.

A detector on the other side of the object picks up the scattered X-rays and turns them into an image. Denser parts of your body, such as bone, show up as clear areas on the X-ray image. Softer parts of your body, such as your flesh and organs, show up as darker areas.

You don't need to do anything special to prepare for an X-ray. A technologist will usually escort you to a room where you can stand or sit, and they may strap your body part in place, much like a seatbelt, to hold it still. You might be asked to wear a gown for medical reasons, such as to protect your private areas. If you are pregnant, you should let the technologist know, because X-rays can harm developing fetuses.

How do X-rays work?

X-rays are a form of electromagnetic radiation (EM) that have a very short wavelength and carry high energy. This allows them to pass through many materials, including our bodies. They are similar to gamma rays, visible light, and radio waves on the EM spectrum.

As X-rays pass through your body, different tissues and bones absorb them at different rates. This creates a shadow on the tissue that can be picked up by a sensor, or film, which produces an image of your body. Denser parts of the body, such as bones, show up clearly as white areas on the X-ray image while softer areas, such as your heart and lungs, appear darker.

To make the images more interpretable, X-ray systems use color to differentiate between various types of materials. For example, organic materials – such as wood, paper and different fabrics – appear orange. Inorganic materials – such as metals – appear blue. If a mixture of organic and inorganic material appears, such as tennis balls inside of a suitcase, it will be shown as green.

X-rays do not affect most items that are sent through the scanner, but they can damage certain sensitive items, such as highly-sensitive photographic or cinematographic film. In these cases, it may be necessary to open the bag for a closer inspection by security officers.

What are the different types of X-rays?

For many years, X-ray baggage scanners have helped to keep passengers safe when travelling by plane or train. The machines use non-ionizing radiation and continue to improve as new security risks emerge so that passengers can travel with peace of mind.

The X-ray tube is lined with lead, which absorbs the X-rays as they pass through the item to be inspected. The X-rays then enter the detector, where they create an image of the contents of the bag or package. The different materials appear in varying colours on the resulting image. The colours are interpreted by inspection personnel using a computer program.

Organic matter, such as food or plastics, shows up in orange on the screen, while inorganic materials, like metals, show up in green. Substances that are too dense to allow the X-rays to pass through them, such as salt or glass, appear black.

During the scanning process, the passenger must remove any sharp objects that may be present in their luggage such as knives or firearms. They should also remove items that could pose a danger to other passengers or airport personnel, such as hazardous chemicals and liquids.

There are various types of X-ray scanners available on the market, with the choice depending on the types of items that need to be scanned and the security requirements of the facility. Atom Physics offers a range of X-ray inspection systems to suit all needs, from small-scale personal baggage scanners for offices and airports through to large freight X-ray machines for ports and rail transportation stations. Contact us today to discuss your specific security needs.

What are the benefits of X-rays?

X-rays are a type of electromagnetic radiation, similar to radio waves, microwaves, visible light and gamma rays. They have enough energy to shift electrons from atoms in a material, leaving them free to interact with other atoms or molecules. Those interactions produce ionization and radiographic images.

When X-rays pass through an object, some are absorbed by the material and some are reflected. The reflected X-rays are picked up by a detector and recorded as an image. A computer circuit compares the pick-ups to create an image of the object. The X-rays that aren’t absorbed or reflected are blocked by the target material, such as lead or steel, and are not seen on the image.

Medical X-rays can detect fractures, tumors and other abnormalities. They can also reveal internal structures, such as blood vessels, bone marrow and the digestive tract. X-rays can be used to diagnose and treat many medical conditions, including bone cancer, heart disease, lung disorders and infections.