Date of Award
7-3-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Colorectal cancer is the 2nd leading cause of cancer death in the United States and the incidence among population under 50 years old has been increasing for the past decade. Contrary to obvious vascular and morphological structures in pre-treatment colorectal cancer, during treatment and post-treatment colorectal cancer tissue often contains fibrosis and edema in tumor bed. These complications cause difficulties in evaluating tissue response to neoadjuvant chemoradiation therapy with MRI and endoscopy, leading to unnecessary resection of rectum, which increases healthcare cost and impacts patient quality of life. Photoacoustic (PA) imaging is a promising tool for observing blood distribution in tissue without the need for exogenous contrast agents. It has been shown to have potential in colorectal cancer treatment monitoring, but prototype systems need to be optimized for reliable patient studies. To address this challenge, development of a robust PA endoscopic imaging system is needed, as well as extraction of quantitative functional information based on signal processing pipelines. This thesis work first improves upon the acoustic resolution photoacoustic and ultrasound imaging system developed previously, with respect to system electronics, mechanics, programming, and optics. The system’s maneuverability is greatly enhanced, and signal integrity is significantly improved. Then a second-generation system was developed for higher portability and reduced footprint, both systems were characterized thoroughly for its performance, and the processing pipeline was optimized with signal from tissue mimicking imaging phantoms. Two quantitative functional information processing pipeline was implemented. The former is a photoacoustic doppler processing to obtain blood flow information from in vivo patients. The algorithm is validated with flow phantoms and used to study blood flow profile in vivo. The latter is a photoacoustic and ultrasound elastography processing algorithm. Tissue mimicking elastography phantoms were developed to assess the algorithm, which is latter applied to ex vivo imaging of colorectal tissue. Both the PA doppler and PA & ultrasound elastography offer added quantitative functional information to morphology and tissue vascular distribution. The design and implementation of the PA endoscopic imaging system as well as photoacoustic doppler and photoacoustic elastography represent readiness in clinical translation of photoacoustic imaging for rectal cancer treatment monitoring. From experimental characterization to validation and optimization via ex vivo imaging, to in vivo imaging in operating room and endoscopic suites in the future, the PA endoscopic imaging system has shown its potential in clinical application and suitability to future large scale clinical trials.
Language
English (en)
Chair
Quing Zhu