The rise in the temperature is measured.

1
Photothermal spectroscopy
Rotem Neeman Yonat Milstein under the
supervision of Prof. Israel Gannot, Dr. Moshe Ben
David Michal Tepper The Lasers Optics in
Medicine Laboratory, Department of Biomedical
Engineering , Faculty of Engineering, Tel Aviv
University

• 1. Introduction
• Spectroscopy of biological tissues is a powerful
  tool for evaluation of tissue composition and
  functionality.
• Photothermal spectroscopy is a method for
  performing tissue spectroscopy, based on
  measuring tissue thermal changes due to light
  excitation.
• Using this method allows estimating the tissues
  oxygenation level, which is a significant value.

• The algorithm- stage 1

The temperature is estimated using a curve
fitting algorithm

• 2. Objective
• Developing a thermal imaging method to determine
  the oxygenation level of a tissue.
• Developing an ideal measuring method.
• Evaluating an existing algorithm for measurement
  analysis.

• The algorithm- stage 2

The temperature increase, ?T, is normalized
according to intensity

• 3. The method
• Illuminating a tissue by a laser will cause a
  temperature increase.
• The temperature increase depends on tissue
  composition, its optical properties and the
  exciting laser wavelength.
• Using several wavelengths for the excitation will
  allow us to estimate tissue composition.

• The algorithm- stage 3

• There is a linear relation between the
  temperature difference and the effective
  absorbance.

Laser
Tissue

• S, the blue material ratio, is unknown and will
  be estimated using the curve fitting algorithm.

• Materials Methylene Blue, Indocyanine Green
  (ICG).
• Setup TiSapphire laser, ThermoVision A40 IR
  thermal camera.

5. Results
1-layer phantoms
4. The Experiment
2-layer phantoms

• Creating the phantoms using various
  concentrations of the two materials mixed with
  agar.

Using phantoms with an upper absorbing layer,
ink, which simulates a complex tissue.

• The rise in the temperature is measured.

• Illumination the phantoms in different
  wavelengths.

• 6. Conclusions
• We were able to determine a good measuring
  method.
• The algorithm was able to estimate the phantoms
  composition relatively well, all experiments
  had an error RMS lower then 10.
• The main problem we encountered was the
  sensitivity of the measurements to environmental
  changes which affected the results.