Research: Time-resolved optical imaging

Schematic picture of a time-resolved optical imgaing set-up

Currently X-ray mammography is the breast-screening method of choice. However, this technique has a number of drawbacks, increasing the interest in noninvasive optical techniques that utilize near-infrared radiation. Whereas conventional diaphanography uses continuous light and shadow imaging, the new technology employs pulsed light sources and time-gated detectors. Wavelengths of interest are in the range 650 - 1300 nm: Near-infrared passes through the tissue with much less loss than visible light. The dilemma encountered with optical imaging of human breasts is that although the wavelength of the light can be chosen such as to minimize the absorption it is impossible to avoid the blurring of the images due to scattering by the tissue.

A systematic study of the time-resolved optical imaging technique has shown that it is highly sensitive with respect to spatial variations in the absorption or scattering factors, in particular under conditions that are similar to those of biological systems of interest. As experiments show that there seems to be no obvious relationship between the properties of the object(s) and the measured intensity profiles, simulations based on realistic models may be essential for the interpretation of the experimental data.

We have devised a novel algorithm and image analysis tools to perform simulations of the time-resolved optical imaging technique. Our simulation method reproduces, without parameter fitting, the experimental transillumination data for realistic tissuelike phantoms. We have used our simulation method to devise a data processing technique to enhance the image quality.

Selected publications:
  • K. Michielsen, H. De Raedt, J. Przeslawski, and N. García,
    "Computer Simulation of Time-Resolved Optical Imaging of Objects Hidden in Turbid Media"
    Phys. Rep. 304, 89 - 144 (1998)
  • K. Michielsen, H. De Raedt and N. García,
    "Time-gated transillumination and reflection of biological tissues and tissuelike phantoms: Simulation versus experiment",
    J. Opt. Soc. Am. A14, 1867 - 1871 (1997)
  • K. Michielsen, H. De Raedt and N. García,
    "Computer simulation of time-gated transillumination and reflection of biological tissues and tissuelike phantoms",
    Med. Phys. 24, 1688 - 1695 (1997)
  • Time-resolved Optical Imaging of Tumors in Human Tissue