Scanning Photoacoustic Imaging And Its Biomedical Applications

Photoacoustic imaging (also called optoacoustic imaging), which has come a long way in the last several years, is a promising imaging modality for biomedicine. Based on the photoacoustic effect, the technique can be used to map the energy deposition of biological tissue by detecting laser-induced ultrasound signals. So, the photoacoustic imaging which combines the advantages of optical and ultrasonic imaging can functionally images the biological tissue at high resolution and high contrast in relatively large depth. In view of the unique characteristics of photoacoustic imaging, a scanning photoacoustic imaging system which utilizes a focused ultrasound transducer is developed. And, the preliminary study of scanning photoacoustic imaging system for some biomedical applications which include early detection of breast cancer, assessing of port wine stain and imaging of blood vessels in the skin are investigated.The main works of this thesis are as follows:(1) The developing of photoacoustic imaging is reviewed, including mechanism, techniques and its biomedical applications. Then some personal views of development of photoacoustic imaging are presented.(2) We designed the program for the project of scanning photoacoustic imaging system, and then constructed the corresponding experimental setups. The control software of system, which includes instrument control and data processing, is developed by LabVIEW.(3) Scanning photoacoustic mammography, utilizing a focused transducer with extended focal zone, is studied. Phantom experiments demonstrate that the location, size and optical energy deposition of absorbers can be visualized correctly.(4) We explored the feasibility of focused photoacoustic depth profiling for port wine stain assessing. Phantom experiments show that epidermal melanin content, depth and thickness of port wine stain layer can be evaluated properly. Preliminary study shows that this method could be potential in diagnosis of PWS skin. (5) A scanning photoacoustic imaging system which implements to image the deep blood vessels of skin is constructed. Blood vessel at depth of 5 mm in skin phantom can be imaged in three dimensions.