Laser-induced ultrasound transmitters for biomedical imaging

Laser-induced ultrasound (LIUS) is a technique to generate ultrasound through the absorption of short laser pulses and subsequent rapid thermal expansion. The properties of the generated ultrasound pulses depend on the optical absorption properties of the absorbing medium, which in turn can also depend on the wavelength of the light. Based on this knowledge it is possible to precisely design a desired photoacoustic response from a LIUS transmitter to perform various kinds of biomedical imaging. Potential benefits of LIUS-based imaging and diagnostics are the possibility to miniaturise transmitters compared to more conventional approaches, lack of sensitivity to electronic cross talk in dense ultrasound detector arrays, and the ability to easily generate broadband pulses. The ability to influence the shape of the LIUS field by changing the illumination geometry gives flexibility to use a single transmitter for multiple distinct applications. While LIUS imaging is already well-established in the field of non-destructive testing of mechanical components, it is a relatively new contender in biomedical imaging, providing many new avenues of research. The purpose of this thesis is to explore the use of LIUS for the imaging of larger organs, particularly the human breast. It will continue the exploration of the potential of LIUS in 2-dimensional, linear array-based, ultrasound imaging. The design and development of transmitters for tomographic imaging, geared towards use in a hybrid photoacoustic/ultrasound breast tomographic breast imaging device, also known as the PAMMOTH system, will be central to the work.