Abstract
Blood vessels play an important role in many significant disease researches such as cancer study. Photoacoustic imaging is a novel bio-imaging modality based on the photoacoustic effect. For micro-vasculature imaging, it owns the advantages of label free high optical absorption contrast and can be performed non-invasively. It also can provide blood-related functional imaging capability for the measure of total hemoglobin concentration and hemoglobin oxygen saturation. In this thesis, we developed an unfocused ultrasound transducer based laser scanning optical resolution photoacoustic microscope (OR-PAM) for extended large field of view (FOV) in vivo micro-vasculature imaging of small animals. Conventional OR-PAM employs a focused ultrasound transducer to improve the signal-to-noise ratio and performs mechanical scanning for imaging. However, mechanical scanning is time-consuming. Such a problem is solved by optical scanning in this study while the optical objective lens and focused ultrasound transducer limit the FOV instead. In our design, the FOV is improved by using an unfocused ultrasound transducer plus laser scanning. The experimental results showed that the developed OR-PAM is with axial resolution of 120m and lateral resolution of 4m when using a 10-MHz unfocused transducer. The achievable FOV is at least 2x2 mm2. The resolving power of the system was also demonstrated by imaging the in vivo micro-vasculature of a mouse ear. The estimated noise-equivalent penetration depth is 0.8 mm in vivo. Future work will focus on the improvement of the imaging frame rate and spatial resolution and the development of multi-wavelength functional micro-vascular imaging.