From X-rays to T-rays

Imagine life before X-rays, before the convenience of being able to “see” broken bones and cancer cells. I’ve seen X-rays of my teeth, the digestive tract of my dog, and the inside of my cat (thankfully, with no missing needle inside). We owe a lot to the discovery (in 1895) of this invisible beam of radiation, and the realization of how the X-ray could revolutionize medical practice.

However, the X-ray isn’t perfect. Even the relatively low amount of radiation used in regular X-rays can cause radation poisoning, which is why the higher amounts used in radiation therapy for cancer patients causes their hair to fall out. As well, X-rays can’t reliably image soft tissue, and they can’t (notwithstanding X-ray’s popularity as a type of super-hero vision) show someone’s naked body under their clothes.

Now that’s a job for the T-ray! Research on T-rays (or terahertz radiation) has been ongoing for a couple of decades, starting with a focus on astronomical research. T-rays fit somewhere on the spectrum of light between infrared and microwaves. Unlike X-rays, they can’t “see” your bones… but they can “see” your skin. Because the T-rays are relatively weak, they also can’t see through metal or water.

Early evidence suggests they can detect some cancer cells, and because T-ray radiation is non-ionising it should be a lot safer than an X-ray. The one problem is T-rays penetrate skin to a depth of only about 4 millimetres: fine for detecting skin cancers but not those deeper down. But now researchers have found T-rays can go deeper in breasts because fatty tissue is more transmissive, up to depths of 2 centimetres.

T-rays could help also solve the mystery of how the universe was formed. In July 2008 the European Space Agency will launch the Herschel Space Observator (HSO) which, with a 3.5m-wide lens, will be the largest space telescope ever launched. The HSO will be the first to observe skies using the terahertz range, allowing scientists to peer further into our universe than ever before, and to see large parts previously unobserved that are simply too cold to radiate wavelengths elsewhere in the spectrum.

As well, it’s the perfect application for a paranoid public, and the burgeoning business of airport security. A story today on the BBC website reports that a passive T-ray scanner may soon be part of security equipment at UK airports. With its ability to see through clothes, the T-ray has the ability to spot weapons and drugs much easier than the current system.

Oh, and just in case you’re worried about peeping security guards, it’s only the low-wavelength T-rays that can show the contours of your body, but higher frequencies are necessary to detect weapons. So the image above is a bit misleading; the photo to the right is closer to what this T-ray scanner would produce.

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Related Links:
Popular Mechanics: “Ixnay on the Xray”
BBC: “Camera ‘looks’ through clothing”
“Airports test terahertz imaging”
“Catching T-waves”
Guardian: Terahertz rays beam past hype”
“Terahertz Radiation”