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Medical Physics / Volume 37 / Issue 7 / OPTICAL PHYSICS

Med. Phys. 37, 3744 (2010); http://dx.doi.org/10.1118/1.3456441 (8 pages)

Assessment of ultrasound modulation of near infrared light on the quantification of scattering coefficient

M. Suheshkumar Singh1, Phaneendra K. Yalavarthy2, R. M. Vasu3, and K. Rajan1

1Department of Physics, Indian Institute of Science, Bangalore 560012, India
2Supercomputer Education and Research Centre, Indian Institute of Science, Bangalore 560012, India
3Department of Instrumentation, Indian Institute of Science, Bangalore 560012, India

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(Received 28 January 2010; accepted 2 June 2010; revised 2 June 2010; published online 28 June 2010)

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Purpose: To assess the effect of ultrasound modulation of near infrared (NIR) light on the quantification of scattering coefficient in tissue-mimicking biological phantoms.
Methods: A unique method to estimate the phase of the modulated NIR light making use of only time averaged intensity measurements using a charge coupled device camera is used in this investigation. These experimental measurements from tissue-mimicking biological phantoms are used to estimate the differential pathlength, in turn leading to estimation of optical scattering coefficient. A Monte-Carlo model based numerical estimation of phase in lieu of ultrasound modulation is performed to verify the experimental results.
Results: The results indicate that the ultrasound modulation of NIR light enhances the effective scattering coefficient. The observed effective scattering coefficient enhancement in tissue-mimicking viscoelastic phantoms increases with increasing ultrasound drive voltage. The same trend is noticed as the ultrasound modulation frequency approaches the natural vibration frequency of the phantom material. The contrast enhancement is less for the stiffer (larger storage modulus) tissue, mimicking tumor necrotic core, compared to the normal tissue.
Conclusions: The ultrasound modulation of the insonified region leads to an increase in the effective number of scattering events experienced by NIR light, increasing the measured phase, causing the enhancement in the effective scattering coefficient. The ultrasound modulation of NIR light could provide better estimation of scattering coefficient. The observed local enhancement of the effective scattering coefficient, in the ultrasound focal region, is validated using both experimental measurements and Monte-Carlo simulations.

© 2010 American Association of Physicists in Medicine

Article Outline

  1. INTRODUCTION
  2. METHODS AND MATERIALS
    1. Experimental measurements
    2. Monte-Carlo based measurements for varying μs
    3. Experimental measurements for varying μa
  3. RESULTS AND DISCUSSION
  4. CONCLUSIONS
Digital Object Identifier
http://dx.doi.org/10.1118/1.3456441

KEYWORDS and PACS

Keywords

biological effects of optical radiation, biomedical optical imaging, biomedical ultrasonics, bio-optics, CCD image sensors, infrared imaging, light scattering, Monte Carlo methods, optical tomography, phantoms, tumours, ultrasound-modulated optical imaging, scattering enhancement, photon migration, path length spectroscopy

PACS

  • 87.50.W-

    Optical/infrared radiation effects

  • 43.80.Sh

    Medical use of ultrasonics for tissue modification (permanent and temporary)

PUBLICATION DATA

ISSN

0094-2405 (print)  

Publisher

$abstract.society.value is a Member of CrossRef American Association of Physicists in Medicine

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