Probing Biological Tissues and Phantoms with Quasi-Coherent Polarized Light Based on Ultrafast Lasers

孫家偉(Chia-Wei Sun)

《光學工程》 85期 (2004/03) Pp. 7-25

https://doi.org/10.30011/OE.200403.0002

並列摘要

Although various optical imaging techniques have been developed, the polarization characteristics of light propagation in tissues have not fully utilized. In this research, we developed several novel techniques for efficient optical imaging based on various polarization discrimination methods. To explore the polarization-dependent optical properties of chicken breast tissues, we calibrated the extinction coefficients of the polarization components parallel with and perpendicular to tissue filaments and the cross-polarized intensity-coupling coefficients between the two polarization components, based on the measured snake-photon intensity data.
Time-resolved Stokes vector components of transmitted light through filamentous tissues were measured for improving the imaging quality of optical images in such tissues. Temporal profiles of the Stokes vectors and the time-resolved degree of polarization (DOP) were calibrated to achieve higher image resolution and contrast, when compared with the images based on only time-gating and/or polarization discrimination. Time-resolved Stokes vectors of transmitted optical signals were measured to differentiate normal and stunned myocardium tissues. The corresponding Mueller matrices were calculated based on the Stokes-Mueller formalism. Our experimental results indicated that the time-resolved Mueller matrices could provide information about myocardial architectural alteration in stunned myocardium.
We also demonstrate a novel method for target depth determination in a turbid medium with experiments. This method relies on the strong dependence of transmitted co-polarized intensity on target depth. Such dependence originates from the inclusion of certain diffuse photons in the co-polarized intensity. A target of stronger scattering located closer to the transmitter results in stronger photon divergence and hence weaker co-polarized intensity at the receiver of a finite aperture. It is shown that an appropriate time gating process could help in improving the accuracy of target depth.
A polarization-sensitive optical coherence tomography (PSOCT) system using an fslaser as the broadband light source is implemented with the axial resolution reaching 5 mm in free space. Through the design of path length difference between the two polarization inputs and the modulation of one of the polarization inputs, the PSOCT images of various input and output polarization combinations can be distinguished and simultaneously collected. The PSOCT system is then used for in vitro scanning the myocardium tissues of normal and infarcted rat hearts. The destruction of the birefringence nature of fiber muscle in the infarcted heart can be clearly observed.

並列關鍵字

Biomedical imaging ； Polarization imaging ； time-gating method ； depth determination ； optical coherence tomography ； skeletal muscle ； myocardial tissue