1. Soumyajit Sarkar, Murali K, and Hari M. Varma, “Tunable dynamical tissue phantom for laser speckle imaging,” Biomed. Opt. Express 15 (2024), 4737-4748.
  2. Murali, K., and Hari M. Varma. “Laser speckle simulation tool based on stochastic differential equations for bio imaging applications.” Biomedical Optics Express 13.12 (2022): 6745-6762. 
  3. Paul, Ria, K. Murali, and Hari M. Varma. “High-density diffuse correlation tomography with enhanced depth localization and minimal surface artefacts.” Biomedical Optics Express 13.11 (2022): 6081-6099.
  4. Paul, Ria, K. Murali, Sumana Chetia, and Hari M. Varma. “A simple algorithm for diffuse optical tomography (DOT) without matrix inversion.” Biomed. Phys. Eng. Express  8 (2022) 045001
  5. Murali, K. and Hari M. Varma “Multi-speckle diffuse correlation spectroscopy to measure cerebral blood flow.” Biomedical optics express 11 (2020): 6699–6709.
  6. Murali, K., A. K. Nandakumaran, and Hari M. Varma. “On the equivalence of speckle contrast-based and diffuse correlation spectroscopy methods in measuring in vivo blood flow.” Optics Letters 45.14 (2020): 3993-3996.
  7. Murali, K., A. K. Nandakumaran, Turgut Durduran, and Hari M. Varma. “Recovery of the diffuse correlation spectroscopy data-type from speckle contrast measurements: towards low-cost, deep-tissue blood flow measurements.” Biomedical optics express 10, no. 10 (2019): 5395-5413.
  8. Dragojević, Tanja, Hari M. Varma, Joseph L. Hollmann, Claudia P. Valdes, Joseph P. Culver, Carles Justicia, and Turgut Durduran. “High-density speckle contrast optical tomography (SCOT) for three dimensional tomographic imaging of the small animal brain.” NeuroImage 153 (2017): 283-292.
  9. Dragojević, Tanja, Danilo Bronzi, Hari M. Varma, Claudia P. Valdes, Clara Castellvi, Federica Villa, Alberto Tosi, Carles Justicia, Franco Zappa, and Turgut Durduran. “High-speed multi-exposure laser speckle contrast imaging with a single-photon counting camera.” Biomedical optics express 6, no. 8 (2015): 2865-2876.
  10. Valdes, Claudia P., Hari M. Varma, Anna K. Kristoffersen, Tanja Dragojevic, Joseph P. Culver, and Turgut Durduran. “Speckle contrast optical spectroscopy, a non-invasive, diffuse optical method for measuring microvascular blood flow in tissue.” Biomedical optics express 5, no. 8 (2014): 2769-2784.
  11. de la Rosa, Xavier, Alvaro Cervera, Anna K. Kristoffersen, Claudia P. Valdés, Hari M. Varma, Carles Justicia, Turgut Durduran, Ángel Chamorro, and Anna M. Planas. “Mannose-binding lectin promotes local microvascular thrombosis after transient brain ischemia in mice.” Stroke 45, no. 5 (2014): 1453-1459.
  12. Varma, Hari M., Claudia P. Valdes, Anna K. Kristoffersen, Joseph P. Culver, and Turgut Durduran. “Speckle contrast optical tomography: A new method for deep tissue three-dimensional tomography of blood flow.” Biomedical optics express 5, no. 4 (2014): 1275-1289.
  13. Nandakumaran, Akambadath Keerthiyil, Hari M. Varma, and R. M. Vasu. “Analysis of the inverse problem associated with diffuse correlation tomography.” Journal| MESA 3, no. 1 (2012): 79-97.
  14. Varma, Hari M., Kuriyakkattil P. Mohanan, Nuutti Hyvönen, Akambadath K. Nandakumaran, and Ram M. Vasu. “Ultrasound-modulated optical tomography: recovery of amplitude of vibration in the insonified region from boundary measurement of light correlation.” JOSA A 28, no. 11 (2011): 2322-2331.
  15. Varma, Hari M., B. Banerjee, D. Roy, A. K. Nandakumaran, and R. M. Vasu. “Convergence analysis of the Newton algorithm and a pseudo-time marching scheme for diffuse correlation tomography.” JOSA A 27, no. 2 (2010): 259-267.
  16. Varma, H. M., B. Banerjee, A. K. Nandakumaran, R. M. Vasu, and D. Roy. “Pseudo-time marching schemes for inverse problems in structural health assessment and medical imaging.” Current science (2009): 1220-1226.
  17. Varma, Hari M., A. K. Nandakumaran, and R. M. Vasu. “Study of turbid media with light: Recovery of mechanical and optical properties from boundary measurement of intensity autocorrelation of light.” JOSA A 26, no. 6 (2009): 1472-1483.
  18. Varma, Hari M., R. Mohan Vasu, and A. K. Nandakumaran. “Direct reconstruction of complex refractive index distribution from boundary measurement of intensity and normal derivative of intensity.” JOSA A 24, no. 10 (2007): 3089-3099.

  • Murali Krishnamoorthy; Soumyajit Sarkar; Susweta Das and  Hari Varma, “A Stochastic optimization approach to laser speckle contrast imaging for a better estimation of blood flow (JTu2A.200)” CLEO 2024, Charlotte Convention Center, Charlotte, North Carolina, USA,  5-10 May 2024.

  • Susweta Das , Ria Paul , Soumyajit Sarkar , Makrand Rakshe , Prasanna Gandhi, and Hari M Varma, “A microfluidic based cerebral perfusion phantom for laser speckle imaging in small animals, Oral Presentation, European Conferences on Biomedical Optics 2023, Munich, Germany, 25-29 June,2023

  • Soumyajit Sarkar, Murali K, and Hari M Varma, “Development of a tunable dynamical tissue phantom for laser speckle imaging of blood flow, Oral Presentation, European Conferences on Biomedical Optics 2023, Munich, Germany, 25-29 June,2023

  • Soumyajit Sarkar, Mohammad Zaffar, and Hari M Varma, “Laser speckle correlation microscopy system to image microvasculature perfusion, Poster Presentation, European Conferences on Biomedical Optics 2023, Munich, Germany, 25-29 June,2023

  • Soumyajit Sarkar, Murali K, and Hari M Varma, “A stochastic differential equation-based Monte Carlo simulation to model light propagation in dynamic turbid media.”, Poster Presentation, European Conferences on Biomedical Optics 2023, Munich, Germany, 25-29 June,2023

  • Sivakumar Panneer Selvam , Murali K , Soumyajit Sarkar , Sibi Raj Bhaskaran , and Hari M Varma, “A deep learning approach to enhance the temporal resolution of laser speckle imaging system for blood flow measurement”, Poster Presentation, European Conferences on Biomedical Optics 2023, Munich, Germany, 25-29 June,2023

  • Ria Paul, Susweta Das, Soumyajit Sarkar, Mohammad Zaffar,  and Hari M Varma, “Fiber-conduit based Laser Speckle Contrast Imaging device for point of care diagnostics”, Poster Presentation, European Conferences on Biomedical Optics 2023, Munich, Germany,  25-29 June,2023

  • Ria Paul, Soumyajit Sarkar, Shruti D. Marathe, Murali K, Susweta Das, Nixon M. Abraham, and Hari M Varma, “Functional imaging of olfactory bulb and somatosensory cortex in mice using small-animal blood flow imaging platform” Oral Presentation “Dynamics and Fluctuations in Biomedical Photonics XX, SPIE Photonic West, San Francisco, 28th-2 January 2023.

  • Hari M Varma “Diffuse autocorrelation and speckle contrast based cerebral blood flow imaging: A theoretical and experimental analysis. “ Invited Talk, CLEO 2023, San Jose California, May 2023.

  • Paul, R., Murali, K, and Hari M Varma, A Spatially Weighted Filter Design for High Density Diffuse Correlation Tomography : Biophotonics Conference : Biomedical Optics 24-27 April, 2022 Fort Lauderdale, Florida, United States
  • Murali, K, and Hari M Varma. , A stochastic differential equation based algorithm to simulate laser speckles for deep-tissue blood flow imaging applications: Biophotonics Conference: Biomedical Optics 24-27 April, 2022 Fort Lauderdale, Florida, United States
  • Murali, K., and Hari M Varma Exploring different source configurations for laser speckle-based blood flow measurement system. In European Conference on Biomedical Optics (pp. EM1A-23) (2021, June). Optical Society of America.
  • Paul, R., Murali, K., Chetia, S., and Hari M Varma. A simple algorithm for diffuse optical tomography (DOT) without matrix inversion. In European Conference on Biomedical Optics (pp. EM1A-21). (2021, June) Optical Society of America.
  • Murali, K., and Hari M. Varma. “A low frame rate camera based Diffuse Correlation Spectroscopy (DCS) system to measure blood flow in human adult brain.” In Optical Tomography and Spectroscopy, pp. STu4D-7. Optical Society of America, 2020. (Oral Presentation by first author)
  • Murali, K., A. K. Nandakumaran, Turgut Durduran, and Hari M. Varma. “An in-expensive diffuse correlation spectroscopy system using low frame rate camera.” In Optical Tomography and Spectroscopy, pp. OTu2D-4. Optical Society of America, 2018. (Oral Presentation by first author)

  • Claudia P. Valdes, Hari M. Varma, Tanja Dragojevi ́, Anna K. Kristoffersen , Clara Castellvi ,Carles Justicia , Joseph P. Culver, and Turgut Durduran , “Deep tissue blood flow imaging with speckle contrast optical tomography”, EB 103-62 oral presentation (30 minutes) 24 June 2015,European conference on Biomedical Optics, Munich, Germany. (Second authorship shared with first author)
  • Tanja Dragojević , Danilo Bronzi , Hari M. Varma , Claudia P. Valdes , Clara Castellvi , Alberto Tosi , Franco Zappa , Carles Justicia , Turgut Durduran, “Multi-exposure, continuous laser speckle contrast imaging of mouse brain enabled by a novel single photon avalanche diode (SPAD) array” (oral presentation 10 minutes) XXVIIth International Symposium on Cerebral Blood Flow, Metabolism and Function & XIIth International Conference June 27-30, 2015, Vancouver, Canada.
  • Tanja Dragojević , Danilo Bronzi , Hari M. Varma , Claudia P. Valdes , Clara Castellvi , Alberto Tosi ,Franco Zappa , Carles Justicia , Turgut Durduran, “Single shot multi-exposure laser speckle contrast imaging with a novel single photon avalanche diode (SPAD) array”, oral presentation (30 minutes) 24 June 2015, European conference on Biomedical Optics, Munich, Germany
  • M. Varma, C. P. Valdes, A. K. Kristoffersen, J. P. Culver, and T. Durduran, “Laser Speckle based tomographic imaging of deep tissue blood flow,” ( Oral presentation, Functional Near Infrared Spectroscopy 2014, Ecole Polytechnique Montreal October 10-12 2014)
  • H. M. Varma, C. P. Valdes, A. K. Kristoffersen, J. P. Culver, and T. Durduran, “Speckle contrast optical tomography (SCOT): Reconstructing the three dimensional distribution of blood flow in deep tissues,” (Oral presentation, Biomedical Optics (BIOMED), Optical Society of America (OSA) 2014 ).
  • P. Valdes, H. M. Varma, A. K. Kristoffersen, J. P. Culver, and T. Durduran, “Multi-Exposure and Multi-Distance Speckle Contrast Spectroscopy for Measuring Blood Flow in Deep Tissues,”(Poster presentation, Biomedical Optics (BIOMED), Optical Society of America (OSA) 2014 ).
  • P. Valdes, H. M. Varma, A. K. Kristoffersen, J. P. Culver, and T. Durduran, “Speckle contrast measurements for blood f low imaging in deep tissues,” (23rd International Commission for Optics (ICO) conference, Santiago de Compostela 26-29 August 2014)
  • Nandakumaran, H. M. Varma, and R. M. Vasu, Direct reconstruction of complex refractive index distribution from boundary measurements,” Proceedings in Applied Mathematics and Mechanics , 7, 2010017-2010018 (2007)

    • Hari M Varma, Ria Paul, Soumyajit Sarkar, Susweta Das. “Modular and portable blood flow imaging system for small animals as a whole or in part”,   (Indian Patent 2024) (Applied,pending)

    • Ria Paul, Susweta Das, Soumyajit Sarkar, Mohammad Zaffar, Hari M Varma, “A point-of-care diagnostic system based on laser speckle contrast imaging (lsci) using an image conduit,”  (Indian Patent 2024) (Applied,pending)

    • Soumyajit Sarkar, Murali K, and Hari M Varma, “Tunable phantoms for mimicking flow dynamics in turbid media” (Indian Patent 2024) (Applied,pending)

    • Murali K and  Hari M Varma: “A scanless optical tomographic system” (2022) (Indian Patent) (GRANTED)

    • Murali K and  Hari M Varma: “Systems and methods for high density diffusing wave spectroscopy” (2019-20) (Indian Patent) (PENDING)

    • Turgut Durduran, Claudia Valdes, Anna Kristoffersen, Hari Varma, Joseph Culver “Speckle contrast optical tomography” EP2888994 A1, Europe/US patent applicant: FundacióInstitut de CiènciesFotòniques, Washington University (GRANTED)

Invited talks

  • Hari M Varma“A novel approach based on stochastic calculus for laser speckle imaging” BRICS (Brazil, Russia, India and China) Workshop on Biophotonics – 2024, October 3-5, Manipal University, India.
  • Hari M Varma “ Laser speckle based  bio-imaging“ 5-day Faculty Development Program (FDP – 2024) on “The New Era of Bioengineering: Innovations and Applications”, organized by the Bioengineering Program in the Department of Chemical Engineering at Dr. Vishwanath Karad MIT World Peace University (MIT-WPU). 
  • Hari M Varma “Non invasive blood flow imaging using laser speckles” Synergy Series, Indian College of Radiology and Imaging (ICRI) meets IIT Hyderabad,  6th July 2023.
  • Hari M Varma “Diffuse autocorrelation and speckle contrast based cerebral blood flow imaging: A theoretical and experimental analysis. “ Invited Talk, Advances in Neuroimaging, Conference on Laser and Electro-Optics (CLEO 2023), San Jose California, May 2023.
  • Hari M varma “Bio-imaging using noise: Application of laser speckles for deep tissue blood flow imaging” BRICS workshop on Biophotonics, 2023 (online among different BRICS countries
  • Hari M Varma “Laser speckle contrast based three dimensional tomographic imaging of deep tissue blood flow.” Indigo policy on September 22 & 23, 2016 at IISc, Bangalore.
  • Hari M Varma “Advances in Scientific and Industrial Instrumentation (ASCII-2019): national seminar conducted by the Department of Instrumentation, Cochin University of Science and Technology. “”Diffuse optical tomography: methods and applications” 15-02-2019.

Workshop

  • AICTE ATAL sponsored Faculty Development Program : Sardar Patel Institute of Technology , Mumbai. “ Quantitative  methods in medical imaging” 24/11/2020
    DBT STAR college scheme “ Webinar series on pure and applied mathematics” Vimala college Thrissur, Kerala “ The role of mathematics in medical imaging”, 15 December ,2020. 
  • IEEE EMB Webinar on  “Diffuse optics for in vivo imaging”, IEEE EMBS SBC, IIT Kharagpur, 11 September, 2020.
  • Department of Instrumentation, CUSAT: Students induction program: “A roadmap for an academic career”. 03/12/2020. 
  • One day workshop on optical imaging. Department of Instrumentation and Applied Physics, Indian Institute of Science, “A method to achieve inexpensive diffuse-correlation spectroscopy system” 29/07/2019

We develop systems and methods for light based bio imaging applications. We primarily focus on utilizing light as a probe for non invasive in vivo brain imaging in animals and humans.