ST1: Multiphoton microscopy
Multiphoton microscopy is an important tool for high-resolution, non-invasive imaging of thick biological tissues. It utilizes femtosecond lasers to excite nonlinear optical contrast signals from tissues. By absorbing the energy from two excitation photons, a fluorescence photon or second-harmonic photon can be generated by tissues. The absorption of two photons simultaneously restricted the excitation to be from the focal point of an objective lens. Thus 3-dimentional high-resolution imaging can be obtained by scanning the focal point. Multiphoton microscopy can image single cells and cell-extracellular matrix interactions. It can be applied to image thick tissues to distinguish cancerous and normal tissues. Multiphoton microscopy is a promising method for early cancer detection.
One challenge in multiphoton microscopy is the low signal level that we are detecting. We use a method named single-photon-counting to count the number of photons that have been excited from tissues. In this project, we aim to design a data acquisition system which can perform single photon counting for multiphoton microscopy. Working on this project, students will get significant exposure to lasers, data acquisition, microscopy, and tissue imaging.
ST2: Photoacoustic tissue imaging
Photoacoustic imaging is an emerging field which can perform non-invasive, functional imaging for up to several centimeters in live tissues. In photoacoustic imaging, high energy laser pulses are delivered to tissues. Upon absorbing the laser pulses, ultrasound waves are generated due to localized heating and thermal expansion. An ultrasound detector array collects the ultrasound waves. 2D or 3D images can be reconstructed based on beam scanning and detection of the time-of-flight of the ultrasound waves. Photoacoustic imaging can be used in combination with ultrasound imaging, where ultrasound will provide structural imaging and photoacoustic will provide functional imaging of the distribution of total hemoglobin and blood oxygenation. The application areas include cancer detection and brain study.
The aim of this project is to design a photoacoustic imaging apparatus. Students will become familiar with pulsed lasers, ultrasound equipment, data acquisition, and tissue imaging.
Optical imaging such as optical coherence tomography and multiphoton microscopy has been shown to be promising in detecting cancer in its early stages. When light shines on tissues, tissues can absorb, scatter, and reemit light due to the interaction of light with tissues. Both morphological and functional imaging can be obtained using optical imaging. Optical imaging has higher resolution and sensitivity than other imaging methods such as CT, MRI, and ultrasound. More importantly, light can be guided through tiny optical fibers to access tissue locations that are inaccessible by other imaging methods. For example, an optical-fiber based endoscope can be inserted into the human blood stream to access and image tumors in the brain.
In this project, we aim to design miniature optical-fiber based endoscopes that can be used to access and image internal organs. Students will get significant exposure to lasers, endoscopy, micro-optics, and tissue imaging.
ST4: Student-initiated project in Biophotonics
Student initiated projects are also welcome. Potential topics include spectroscopy, microscopy, endoscopy, tissue imaging, and cellular imaging. Please email me to setup a time to discuss your interest.