| dc.description.abstract | Recently, photoacoustic imaging has emerged as a new hybrid biomedical imaging technique, which provides rich optical contrast information at deep ultrasound penetration depth not achievable with conventional optical imaging techniques. It is expected to find applications ranging from fundamental biological research to clinical diagnosis. In photoacoustic imaging, short pulsed-laser illumination is used to generate high-frequency and wide-band ultrasound waves (i.e., photoacoustic signals) inside the imaging target to be detected by a single-element ultrasound transducer or a transducer array. However, one fundamental issue in current photoacoustic imaging system design is the opaque structure of the ultrasound transducer, which prevents effective and efficient light delivery onto the imaging target and oftentimes results in lower imaging performance and complex and bulky hardware configurations.
To address this issue, new optically-transparent polymer ultrasound transducer and transducer array based on polyvinylidene fluoride (PVDF) have been investigated and their applications in photoacoustic microscopy (PAM) and photoacoustic tomography (PAT) have been demonstrated in this research. Specifically, two microfabrication processes were developed for making transparent PVDF transducers from solid bulk films and liquid precursors. The electrical properties of the transparent PVDF transducers were studied. Impedance matching and amplification circuits were designed accordingly to provide optimal photoacoustic signal conditioning and acquisition. Based on the developed transparent PVDF single-element transducer and transducer array, both PAM and PAT imaging experiment setups have been built, respectively. Their imaging performance, such as sensitivity, contrast, spatial resolution and penetration depth has been characterized with optical phantoms. Preliminary ex-vivo imaging experiments on animal tissues and in-vivo imaging experiments on live small animals have been conducted to demonstrate the feasibility of photoacoustic imaging based on optically-transparent ultrasound transducers. The experimental results show that using optically-transparent ultrasound transducers can significantly improve the light delivery efficiency and reduce the complexity of the imaging system, which will be especially useful for the clinical translation of photoacoustic imaging. | |
