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Laser team uses LIBS to spot cancer

14 Oct 2004

US Scientists reveal the potential of laser induced breakdown spectroscopy (LIBS) as an in vivo tool for diagnosing cancer.

Researchers in the US have shown that laser-induced breakdown spectroscopy (LIBS) can distinguish between normal and malignant tumour cells in tissue samples. A first for LIBS and a boon for the accurate diagnosis and classification of cancer, the team discovered a significant difference in the intensity ratio of trace elements in normal and cancerous material (Applied Optics 43 5399).

LIBS, a simple and robust technique, works by focusing energy from a pulsed laser on to a sample to create a miniature plasma. Analyzing the light emitted by the plasma with a spectrometer reveals the sample's elemental constituents. To date, the technique has analyzed everything from metal parts and archaeological artefacts to explosives and bio weapons (more info).

The team from Mississippi State University uses a frequency-doubled Nd:YAG laser operated at a repetition rate of 10 Hz and with a pulse width of 5 ns at 532 nm in their LIBS setup. An ultraviolet (UV) fused-silica lens focuses the laser beam down to a spot size of 0.04 mm and also collects light emitted from the laser-induced plasma. Two UV-grade quartz lenses couple the LIBS signal to an optical fiber which links the setup to an Echelle optical spectrograph (LLA Instruments) and an intensified CCD camera (Kodak) which records the spectra.

By applying the technique to normal and cancerous canine liver samples the researchers discovered that the intensity ratios of Ca/K and Na/K were significantly higher in the malignant tissue spectra. The result was confirmed using another technique - inductively coupled plasma emission spectroscopy (ICPES).

"Although the result in this study is preliminary, it shows that LIBS has great potential for development as an in vivo diagnostic tool for cancer detection," said the authors in their paper. "Extensive development in this area is needed to obtain quantitative results for practical applications."

James Tyrrell is reporter on Optics.org and Opto & Laser Europe magazine.

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