Theses Doctoral

Wearable Flexible Optical Imaging Systems for Diffuse Optical Spectroscopy and Tomography in Medical Diagnosis and Treatment Monitoring

Kim, Youngwan

The overall goal of this thesis is the development of wearable flexible optical imaging systems (We-FOISs) that can be used for diffuse optical spectroscopy (DOS) and tomography (DOT). The advantages of We-FOISs lie in their low-cost, portability, and simple patient-interface compared to current DOS and DOT systems. A flexible form factor provides conformal attachment even in cases where the targets such as fingers and toes have a strongly curved surface. We-FOIS technology is a scalable and expandable. Each system can be designed with multiple pairs of light sources and photodetectors depending on the needs and size of the target.

The We-FOISs presented in this thesis were developed based on a modular design. The two main modules are a sensing unit and a control unit (a.k.a. sensing band and control band). Two different types of sensing units have been developed. The first type is based on inorganic optoelectronic components such as light emitting diode (LED) and silicon-photodiode (Si-PD). The second type is made with organic components such as organic light emitting diodes (OLEDs), quantum-dot light emitting diodes (QD-LED), and organic photodiodes (OPDs). The flexible control units operate the light sources, read the intensity of the light transmitted through biological tissue, and send data to the computer. Depending on the number of pairs of light sources and photodiodes placed on the flexible sensing bands, the control units have different designs.

Furthermore, a small integrating sphere system (SISS) was developed to measure the optical properties (absorption and scattering coefficients, μa and μs) of biological tissue samples and tissue-mimicking phantoms, which were to be used to calibrate the We-FOISs. The accuracy of the SISS as a function of the sample thickness was investigated by comparing a widely used inverse-adding-doubling (IAD) program and inverse-Monte-Carlo (IMC) simulations.

Finally, the performance of the different We-FOISs were tested in various pre-clinical and clinical applications, including epilepsy monitoring in rat brains, monitoring of peripheral artery disease (PAD) in human feet, diagnosing systemic lupus erythematosus (SLE) in human fingers, and characterizing tumors in breast cancer patients. The results demonstrated the potentials of the We-FOISs for monitoring of symptoms of various diseases and for applications in point of care.


This item is currently under embargo. It will be available starting 2025-01-06.

More About This Work

Academic Units
Electrical Engineering
Thesis Advisors
Hielscher, Andreas H.
Ph.D., Columbia University
Published Here
January 30, 2020