BBC News Online: Sci/Tech

X-ray substitute to test teeth

The system harnesses radiation called terahertz rays, which sit between infrared and microwaves in the electromagnetic spectrum.

These can partly pass through many common materials and can reveal both the structure and composition of the target.

Toshiba Research Europe (TRE) is developing the method at the Cambridge Science Park, UK. Its managing director, Professor Michael Pepper says: "These are very early days, but it is clear that Terahertz Pulse Imaging is going to be very important, particularly in areas where X-rays are insensitive."

Safer, smarter

Terahertz rays are non-ionising and are therefore thought to be safer than X-rays. Also, the power levels needed to produce a sharp image are usually lower than the background terahertz radiation encountered in everyday life.

A key advantage of terahertz analysis is that it can be used in two ways. Firstly, it can reveal three-dimensional shape by measuring how the waves are affected by the structure of the target. This is similar to radar.

Secondly, terahertz analysis can be used to identify the material found in the target. This is done by using a range of terahertz frequencies and measuring which ones the material absorbs. This is called spectroscopic analysis.

Teeth testing

The first application is expected to be in dentistry. Dr Don Arnone is TRE's project leader and says that one mode of use reveals the thickness of a tooth's enamel and while the other displays the internal condition of the tooth.

"We can construct a three-dimensional image of the tooth and rotate it on the computer screen so the dentist can examine each tooth from the optimum angle," he says.

After dentistry, other body tissues will be targeted for the system's development but non-medical applications are also possible.

TRE has demonstrated the usefulness of terahertz waves in quality control in food processing, semiconductor and computer chip manufacture and its ability to find objects hidden in containers.

The recent developments in terahertz technology are due to new, cheaper ways of generating and detecting the waves. To produce them, a semiconductor crystal is bombarded with ultra-fast pulses of visible laser light.

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Internet Links

Toshiba Europe Research
Terahertz Technology Research - University of Reading

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