Photoacoustic Tomography: From Bench to Bedside

Citation

Lin, Li (2020) Photoacoustic Tomography: From Bench to Bedside. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/1DGY-T168. https://resolver.caltech.edu/CaltechTHESIS:12092019-113537728

Abstract

Photoacoustic imaging (PAI) is an emerging imaging modality that shows great potential for preclinical research and clinical practice. As a hybrid technique, PAI uniquely combines the advantages of optical excitation and of acoustic detection. Optical absorption provides a rich contrast mechanism from either endogenous chromophores or exogenous contrast agents. Because ultrasound scatters much less than light in tissue, PAI generates high-resolution images in both the optical ballistic and diffusive regimes, overcoming the limitations imposed by light scattering in deep biological tissues. PAI has led to a variety of exciting discoveries and applications from laboratory research to clinical patient care.

To translate photoacoustic technology from the bench to the bedside, this thesis focuses on efforts to increase the imaging depth, provide clinically useful information (i.e., relevant imaging contrast), reduce system size, and improve system reliability. Assisted by powerful pulsed lasers and advanced data acquisition circuits, modern PAI has achieved applications such as functional imaging of the whole rat brain, revealing detailed angiography and functional connectivity at high spatiotemporal resolution. The advancement of deep imaging in small animal PAI has been transferred to human breast and brain imaging, showing early promise for clinical practice. To further extend the imaging depth and provide dielectric imaging contrast, microwave-based thermoacoustic tomography has been demonstrated in vivo. To map further physiological contrasts, spectroscopic PAI has been performed to image the oxygenation states of hemoglobin and myoglobin. In addition to the effort towards deep penetration and multiple contrasts, benchtop photoacoustic microscopy has been minimized to a handheld probe for human skin imaging. As a rapidly evolving imaging technology, PAI is being translated from the bench to the bedside and promises exciting and useful clinical applications.

Thesis Files