Development of Multi-modal Optical Coherence Tomography Imaging Systems and Probes

Optical Coherence Tomography (OCT) is a powerful imaging modality widely used in medical diagnostics and biological research for its non-invasive, high-resolution, and depth-resolved properties. Additionally, OCT has demonstrated remarkable versatility in various applications. In this thesis, we develop multi-modal OCT systems. We have designed and built a new class of endoscopic OCT that enables imaging inside the human body and a new type of functional OCT that provides information beyond structural characteristics. We combine the chemical specificity of mid-infrared spectroscopy with the morphological capabilities of OCT systems, potentially opening a new class of biomedical applications. First, we develop a swept-source OCT (SS-OCT) system that serves as a benchtop tool and a scalable platform for further functional extension. A conventional galvanometer-scanner-based fiber optics SS-OCT system has been developed with an axial resolution of 7.24 μm at 1310 nm, achieving max imaging depth of 5.98 mm in the air. The A-scan rate is 100 kHz defined by the swept-source and lateral resolution of 24.8 μm defined by the scanning objective. The system has demonstrated a high sensitivity of 96.88 dB and low sensitivity roll-off of 0.6 dB over 5.5 mm imaging depth. We demonstrate the utility of SS-OCT in endomicroscopic applications by developing forward and side-viewing probes. Both classes of probes were designed with cost-efficient scanners while maintaining high performance. The side-viewing probes use a 6 mm diameter micro stepper motor and a custom Gradient Index (GRIN) achieving 26 μm lateral resolution and real-time imaging with a frame rate of 100 fps. The forward-viewing probes are built using a piezoelectric (PTZ) cantilever scanner and a micro lens, enabling a 4 mm diameter probe size while achieving a large field of view (2.25 mm2). Finally, we have developed a novel photothermal mid-infrared spectroscopic imaging (MIRSI) OCT technology. Unlike prior approaches, this new form of functional OCT can provide label-free chemical contrast. The system utilizes a pulsed mid-infrared laser to introduce a modulated photothermal signal into the OCT. This technology combines the three-dimensional (3D) morphological imaging capabilities of OCT with the molecular sensitivity of MIRSI through endogenous contrast without adding nanoparticles of contrast agents. Our approach can obtain co-registered OCT and photothermal MIRSI images with a lateral resolution of 21 μm and 15.6 μm, respectively. The 25 and 45 μm polystyrene (PS) beads and biological samples, including mouse kidneys and mouse brains, are used to demonstrate spatial and spectral imaging fidelity.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Electrical Engineering

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Wu, Xinyu

Advisor dc:contributor.advisor

• Reddy, Rohith

Committee members dc:contributor.committeemember

• Larin, Kirill
• Mayerich, David
• Shan, Xiaonan
• Singh, Kanwarpal

• Physics, Optics
• Engineering, Electronics and Electrical

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/18357

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/18357