PHOTOACOUSTIC IMAGING AND HIGH INTENSITY FOCUSED ULTRASOUND IN BIOMEDICAL APPLICATIONS

Abstract

Optical and acoustical technologies for biomedical devices have been developed rapidly in the past years. These non-invasive technologies are used for diagnostic and therapeutic studies with great potential for improving biomedical applications. In this work, photoacoustic imaging that combines the advantages of optical and ultrasound imaging, and high intensity focused ultrasound (HIFU) treatment enhanced with laser were investigated to understand the application and feasibility of optics and acoustics in biomedical studies. At first, photoacoustic tomography system was used to monitor brain functional activation by monitoring the changes of the blood volume at the cerebral cortex surface of rats induced by cocaine hydrochloride. And, the research was continued with a photoacoustic microscopy (PAM) system. With the PAM system, the brain images were obtained at coronal views, and the regional changes in the total hemoglobin (HbT) concentration were presented. Additionally, a customized photoacoustic imaging system was applied to detect the neuronal activity in the motor cortex of an awake, behaving monkey during forelimb movement. The research results that showed the activated region images demonstrated the capability of photoacoustic imaging. Next, photoacoustic wave propagation was studied using shock wave theory. The propagation was analyzed in non-linear way and simulated to compare the difference between existing linear and non-linear solutions. Further, the combination of laser and HIFU treatment was studied. Cavitation activities and increase of temperature during HIFU treatment were investigated by using in vivo murine animal models. The enhanced results from the HIFU treatment with laser illumination showed the efficacy and potential of the system. The studies of PA imaging and HIFU treatment demonstrate the high feasibility of using optics and acoustics in the biomedical area.