Diffuse optical tomography: Imaging multiple structural and functional features.

다국어 초록 (Multilingual Abstract)

Diffuse Optical Tomography has drawn more and more interests in the biomedical field over the recent couple of decades due to its ability to noninvasively recover not only tissue structural information but also functional and molecular properties. The contrasts that optical parameters could demonstrate in DOT are usually higher than those of the conventional methods. Based on these contrasts, different approaches had been developed applying DOT for imaging, and so far lots of efforts were spent on detecting breast cancer by imaging tissue absorption and scattering coefficients as well as hemoglobin concentration and oxygen saturation level.
In this work, we tried to expand the ability of DOT in breast cancer detection by introducing Phase-contrast diffuse optical tomography (PCDOT). PCDOT uses near-infrared diffusing light to non-invasively reconstruct tissue refractive index (RI) distribution. RI depends on the tissue’s physical and chemical properties and previous study revealed that it might serve as a promising imaging parameter in breast cancer detection. We’ve first developed a 2-step method to improve the PCDOT image both qualitatively and quantitatively at single-wavelength; then we’ve introduced a multispectral PCDOT algorithm to more efficiently reconstruct RI simultaneously with other tissue functional parameters and attempted to improve this algorithm by different structural regularization methods.
Measuring hemodynamic changes, oxygen delivery and cerebral blood flow is important for locating and interpreting pathological variations associated with epileptic disorders. We then further expanded the application of DOT by presenting a method of dynamic, noninvasive and functional diffuse optical brain imaging that is conducted simultaneously with hippocampus CA1 local field potential recordings for anesthetized rats under resting conditions and during acute chemoconvulant provoked seizures. By illuminating the scalp with near-infrared light and recovering, the backward scattered light were collected and three-dimensional (3D) absolute tissue optical absorption images with high temporal resolution were obtained using a finite-element based reconstruction algorithm. The measured tissue absorption changes were validated with optic-intrinsic-signals measurement. In the focal seizure model, the seizure focus could be identified using the technique denoted by local variations of tissue absorption level as well as hemoglobin and cerebral blood flow changes. The findings are consistent with general observations in seizures of significant local cerebral metabolism increase. Successive absorption images along with EEG signals demonstrated linearity relationships from the neurovascular coupling study, suggesting cerebral metabolism closely matches demand from neuronal changes. This preclinical study suggests that this technique is feasible to be applied to human study and can provide insights into brain function and mechanisms of seizure disorders.