Light propagation in the mice s organs optical ray tracing project
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Light Propagation in the Mice’s Organs Optical Ray-tracing Project. Haiyan Xie, Atomic Physics Division Lund University. Outline. Introduction Aim of this project Photodynamic therapy (PDT) Variations of optical parameters, i.e., μ a , μ s , and g, in PDT Experiments and Simulations

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Light Propagation in the Mice’s Organs Optical Ray-tracing Project

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Light propagation in the mice s organs optical ray tracing project

Light Propagation in the Mice’s OrgansOptical Ray-tracing Project

Haiyan Xie,

Atomic Physics Division

Lund University


Outline

Outline

  • Introduction

    • Aim of this project

    • Photodynamic therapy (PDT)

    • Variations of optical parameters, i.e., μa, μs, and g, in PDT

  • Experiments and Simulations

    • Ex vivo absorption spectroscopy

    • FRED simulations

  • Results

  • Discussions


Aim of this project

Aim of this project

  • How PDT works?

  • a) A patient comes to the clinic with a tumour. The photosensitiser is given by injection.

  • b) After time the photosensitiser concentrates in the tumor.

  • c) The photosensitiser is activated by light.

  • d) The tumor is selectively destroyed.

  • (Adapted from http://www.bmb.leeds.ac.uk/pdt/PDToverview.htm)

To simulate the light distribution in the animal organs after the photodynamic therapy (PDT).


Experiments

Experiments

  • A xenon short-arc lamp (white light)

  • Source and detection optical fibers

2 mm fiber seperation 

The path length of the collected

photons is relatively insensitive to

the tissue scattering variations.

Probe

Tumor / Organ

  • Experiments to achive the concentrations of the sensitizer

  • in the tumor or other organs in a mouse

Absorption Spectroscopy


Light propagation in the mice s organs optical ray tracing project

Experiments

Left) Ex vivo absorption spectroscopy measurements, OPS-1000

Biospectrometer TM (Optimum Technologies, Inc), and

Right) Sample tissues.


Fred simulations

FRED Simulations

System geometry in the FRED simulation.

  • collimated light source: 1 W

  • source and detection fibers: 400 mm- and 200 mm- diam

  • size of the tissue: 4 mm diameter * 4 mm height

  • # of rays: 250,000


Optical parameters of the tissue

Optical Parameters of the Tissue

  • 2 mm fiber seperation:

    • Scattering coefficient, ms= 1 mm-1

    • Anisotropy coefficient, g=0.9

  • Absorption coefficient, ma :

    • Varies due to the interactions between the photosensitiser and the tissue:

      The concentrations of different chromophores have been changed.

      • Photosensitizer (mTHPC),

      • Oxyhemoglobin (HbO)

      • Deoxyhemoglobin (Hb)


Light propagation in the mice s organs optical ray tracing project

where

’s  concentration changes

’s  the corresponding extinction coefficients, dependent on the

wavelength

Extinction coefficients of mTHPC, Hb and HbO.

Absorption coefficient

  • The changes of the tissue absorption coefficients :


Light propagation in the mice s organs optical ray tracing project

Absorption of water.

Absorption coefficient

  • It is assumed that the absorption in the tissue is mainly caused by the water with the concentration of 60% initially.


Light propagation in the mice s organs optical ray tracing project

= 0.485mM

= 2.532mM

= 4.797mM

= 188.933mM

= 9.835mM

= 114.574mM

Absorption coefficient

  • Mouse #: DL82 (8 hours after the drug injection)

Absorption coefficients of the mouse tissues


Light propagation in the mice s organs optical ray tracing project

Simulation Results (1)

Tumor:

Simulation:

Measured:


Light propagation in the mice s organs optical ray tracing project

Simulation Results (2)

Liver:

Simulation:

Measured:


Light propagation in the mice s organs optical ray tracing project

Discussions

  • More rays: a much longer simulation time

    A disadvantage of the FRED software when dealing with a scattering process?

  • Very small output power


Light propagation in the mice s organs optical ray tracing project

Thank you!


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