Wavelength-modulated Raman spectroscopy enables tissue assessment in real time

Raman spectroscopy is a powerful tool for tissue classification and disease recognition, although there have been considerable challenges to using the method in a clinical setting. To overcome these challenges, scientists at the University of St. Andrews (Fife, Scotland) and the Institute of Photonic Technology (Jena, Germany) have demonstrated the advantages of wavelength-modulated Raman spectroscopy, opening the door to clinical applications such as real-time assessment of tissues during surgery.

The inelastic scattering of light from any sample, called the Raman effect, yields a molecular fingerprint related to the intrinsic composition of the sample. The technique enables cancerous lesions, which are accompanied by changes in chemical composition compared to normal tissue, to be detected as a vibrational spectroscopic fingerprint. However, there are considerable challenges to using the method in a clinical setting because factors such as ambient light, background fluorescence, and 'etaloning' (a phenomenon that degrades the performance of thinned, back-illuminated charge-coupled devices) can hinder the interpretation of images. Pre-processing the data is prone to introduce artefacts and seriously hamper a classification.

In their study, the researchers recorded Raman signals against a high auto-fluorescence background by studying liver tissue and record spectra of Paracetamol tablets in ambient light.

"The principle of our implementation of wavelength-modulated Raman spectroscopy is that fluorescence emission, ambient light, and system transmission function do not significantly vary, whereas the Raman signals do vary upon multiple wavelength excitation with small wavelength shifts," explains corresponding author Christoph Krafft, PhD, of the Institute of Photonic Technology. "In turn, this leads us to 'cleanly' extract the Raman signature even in the presence of such factors. In the current work, we developed a hardware-based approach to suppress confounding factors in Raman spectra that requires a minimum of pre-processing and offers further unsurpassed advantages."

The study is published in Biomedical Spectroscopy and Imaging; for more information, please visit http://iospress.metapress.com/content/a37522877754u243/fulltext.html.

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