Date of Award
Doctor of Philosophy (PhD)
Human colorectal cancer and ovarian cancer remain the leading causes of cancer mortality. However, if diagnosed early, both cancer types have high patient survival rate. Endoscopic screening and surveillance are particularly helpful in providing physicians with in situ information for diagnosis. Compared to traditional ultrasound endoscopy, optical endoscopy can provide higher imaging resolution with more detailed tissue morphology. Also, differences in tissue optical properties (e.g., scattering, absorption) can also by revealed with optical imaging methods. In this thesis, two optical coherence tomography (OCT) catheters are introduced for ex vivo sample studies and in vivo patient studies to differentiate malignant tumor from benign tissue. A distal-end mini-motor based optical coherence tomography (OCT) catheter is built to investigate the difference between ex vivo human rectal cancer and normal tissue. A convolutional neural network (CNN) is introduced to help classify OCT images of different tissue types. A thin, long, and flexible OCT catheter with helical hollow strand (HHS®) tube providing distal rotation enables investigation of human colorectal polyps (e.g., tubular adenoma (TA), tubular villous adenoma (TVA), and adenocarcinoma) in vivo. The results reveal the structural differences among different polyp types in OCT B scan images. Besides imaging colorectal cancer, the OCT catheter is also applied to image fallopian tubes ex vivo seeking the origin of high grade serous ovarian cancers. By incorporating a feature extraction algorithm, the vasculature and tissue heterogeneity of the fallopian tube can be extracted from 3D OCT images, showing a significant directionality difference between benign and malignant tissue. Photoacoustic tomography (PAT) utilizes a combination of optical excitation and ultrasound detection to enhance imaging depth. A PAT probe requires proper light delivery: the higher the laser energy injected, the better the signal-to-noise ratio. However, the maximum permissible exposure (MPE) limits the laser energy delivered. A fiber tip diffuser is proposed to increase the optical fiber’s numerical aperture (NA), which reduces the laser fluence and enables higher laser energy injection. Also, a fiber diffuser with side diffusive layer coating is proposed to generate side illumination. By controlling the input laser coupling angle and the gradient of the scattering coefficient inside the diffusive layer, a 3-cm long homogeneous illumination pattern can be generated.
Chao Zhou, Ian S. Hagemann, Lan Yang, Matthew Lew,
Available for download on Wednesday, May 15, 2024