Our team focuses on the development of in vivo optical tomography modalities. Optical imaging has many unique advantages, including non-ionizing, high contrast, fast imaging speed and spectroscopic capability. However, strong light scattering in tissue makes it very challenging for optical methods to image objects deep in tissue.

High-resolution optical imaging methods, such as optical microscopy, can only image targets that are less than 1 mm deep in turbid tissue. We are exploring photoacoustic tomography (PAT) to break through this imaging barrier. PAT is a hybrid imaging modality that combines the optical absorption contrast with the ultrasonic detection. When some tissue, such as blood, absorbs the photon energy from the pulsed laser, it will generate ultrasound due to thermal expansion process. Since ultrasound has a much lower scattering coefficient than that of light, PAT can take advantage of the multi-scattered photons to image deep tissue. We have obtained sub-millimeter resolution when imaging objects over one centimeter deep in tissue. We also use spectroscopic PAT to provide functional imaging for subcutaneous objects.

In addition to PAT, we are engaged in research on fluorescence molecular tomography (FMT). Due to strong light scattering, traditional fluorescence imaging generally only provide 2D information, and the image resolution drops quickly as the depth of the fluorophore increases. Based on the study of photon migration in tissue, FMT quantitively reconstructs the fluorophore in 3D version. We currently focus on developing novel non-contact FMT by using CCD camera to acquire fluorescence signal.