Prof. Ramachandra Rao Dasari, Assistant Director of G.R. Harrison Spectroscopy Laboratory and Laser Biomedical Research Center, Massachusetts Institute of Technology, USA recently gave an inspiring talk titled “Shining Light on Human Health” that was organized by Junior Science Club at Center for Integrated Studies, South Campus.


Starting with basics of Interaction of light with matter and Electromagnetic Spectrum he mainly discussed about Raman Spectroscopy which has unique advantages i.e. Raman frequencies are characteristics to the molecule, Qualitative and quantitative information, Selective and sensitive detection, Non-invasive technique, Foremost analytical technique used in Biology, Chemistry, Physics and Engineering. As you are aware, Raman spectroscopy is a fundamental form of molecular spectroscopy that is widely used to investigate the structures and properties of molecules from their vibrational transitions.

Our approach is fairly simple. Light of a specific wavelength is incident on the sample or the subject, as the case may be, and the back-scattered or the transmitted light is collected. The interaction of the incident light with the tissue causes a change in the wavelength of the scattered light. The resultant spectrum is then used in conjunction with the reference blood glucose concentrations to create a calibration model that can be then used prospectively on different subjects or on the same subject at a different time” said Prof. R.R. Dasari.

Talking about research at LBRC, Prof. R.R. Dasari told “We have developed several quantitative phase microscopy techniques which includes Hilbert phase microscopy that measures 2D phase image and Single off-axis interferogram that is measured by Mach-Zehnder interferometer and converted into phase image. However, this setup is sensitive to environmental fluctuations. Diffraction phase microscopy overcomes this problem. We also developed tomographic phase microscopy. By scanning the beam angle like X-ray CT scan, we could generate 3D refractive index tomogram. We’re also developing phase estimation algorithms to improve the sensitivity. Fortunately, most scattering events in the biological tissues are elastic scatterings. Therefore, you can deliver photons to the target position through the tissue if you can control the input beam properties. With advanced technology such as spatial light modulator, this is possible and we are progressing fast.”

He also discussed about Fiber-probe based Raman system and Raman Spectroscopy Based Non-invasive Blood Analyte (Glucose) Sensor. He specifically mentioned Laser-Induced Breakdown Spectroscopy (LIBS) technique for which our university research groups at ACRHEM is very famous.

He also discussed Anatomy of transdermal glucose measurement. “The principal challenge from a physiological standpoint arises from the time lag between the glucose levels in the blood and so-called interstitial fluid compartments. To address this issue, we developed the dynamic concentration correction methodology. Our solution strategy is to introduce a mass transfer formulation, which with the help of simplifying assumptions reduces to the incorporation of the rate of change in concentration into the overall equation.”

“Nevertheless, despite the recent innovations, our recent clinical studies at the MIT Clinical Research Center have shown that the lack of reproducibility of the tissue site.  To overcome this problem, we plan to incorporate an active mechanical tissue modulation interface in association with Professor Harry Asada @MIT, Mechanical Engineering. Inspired by the concept of difference spectroscopy, we will use appropriate pressure modulation on the measurement site to preferentially isolate the spectra of the subsurface mobile components relative to the surface static tissue. This will serve to enhance the signal from the blood analyte components (e.g. blood glucose), improve signal reproducibility over time by suppressing skin tissue signals. “

He concluded his talk with investigation of Cancer Diagnosis using Multi-Modal Spectroscopy specifically Spectroscopic Cancer Diagnosis and Imaging development of novel, cutting edge technology for cancer diagnosis and imaging.

By Harshavardhan Reddy Pinninty, Integrated MSc Physics student at School of Physics