Student Theses

Optical coherence tomography for non-invasive diagnosis of basal cell carcinoma (Thesis)

Basal cell carcinoma (BCC) is the most common form of skin cancer. In Caucasian populations, one in five to six people will develop a BCC during their lifetime.1-3 As the incidence of BCC continues to rise, it is an important health problem worldwide, involving high healthcare costs. According to current (inter)national guidelines, lesions clinically suspected for BCC require a punch biopsy to confirm diagnosis and histopathological subtype.4, 5 A punch biopsy is an invasive procedure with several disadvantages, including pain and discomfort for the patient, scarring, delay in the diagnostic process and costs for the healthcare system. Due to the high volume of BCCs, there is an increasing focus on novel diagnostic methods. In an ideal situation, a non-invasive diagnostic method can (partly) replace the need for a biopsy, so that diagnosis and treatment of BCC can be accomplished in one day. This so-called ‘one-stop shop’ approach could thus result in a reduction of the number of bi...

Optical Coherence Tomography as a Biomarker in Amnestic Mild Cognitive Impairment: an Umbrella Review of Systematic Reviews (Thesis)

Introduction: People with mild cognitive impairment (MCI) are at a higher risk of developing Alzheimer’s disease (AD), one of the most expensive diseases that lead to death and burden society. Therefore, early diagnosis is crucial to implement early and optimal AD treatment and prevent or delay disease progression. As a part of the central nervous system, the retina provides a unique and easy method for studying neurodegenerative disorders. Purpose: The aim of this review was to screen existing systematic review results to describe the relationship between amnestic MCI and changes in the retinal layers measured with optical coherence tomography (OCT). Methods: An umbrella review of English literature of systematic reviews was conducted on 1 October 2022 in three electronic databases (PubMed, CINAHL and MED-LINE). Studies of retinal thickness measurements by OCT in ageing people with amnestic MCI were screened from the past ten years. Studies with not related OCT and...

Image Analytic Tools for Optical Coherence Tomography Tissue Characterization and Robust Learning (Thesis)

The computer-aided analysis is poised to play an increasingly prominent role in medicine and healthcare. Benefiting from the increasing computing power, various machine learning frameworks have been developed in the biomedical field, bringing significant improvements in real-world clinical applications. However, for many diseases, the development of these life-supporting algorithms is still in its infancy. To bridge this gap: This thesis is dedicated to the development of efficient algorithms for better image intervention and addressing data quality challenges in machine learning algorithms to provide direct guidance for real-world clinical applications. With the above goals, three topics are explored in depth. First, we develop a novel tissue analysis framework for cardiac substrate identification and tissue heterogeneity assessment. In particular, we creatively used model uncertainty to measure tissue structure information, offering a means of extracting the tissue heterogen...

Development and Application of Polarization Sensitive Optical Coherence Tomography

Optical coherence tomography (OCT), a three-dimensional optical imaging technique based on low coherence interferometry, can be extended to measure the functional property of the biological sample. As a functional extension of OCT, polarization sensitive optical coherence tomography (PSOCT) enables 3D imaging of the anisotropic biological samples, such as scar, tendon, muscle, collagen, and nerve fiber bundles. This thesis focuses on the development and application of PSOCT. This goal includes four specific aims. The first aim is to develop a single input PSOCT imaging system with an improved image contrast. To achieve this aim, the polarization state is utilized as the imaging parameter and visualized using the Stokes parameters-based color-encoded algorithm. The second aim is to develop an algorithm that can derive depth-resolved polarization parameters with the single input PSOCT system. Towards this aim, a PSOCT-based polarization state transmission model is proposed. Based on t...

Quantitative dynamic cellular imaging based on 3d unwrapped optical coherence phase microscopyoptical coherence phase microscopy (Thesis)

Phase wrapping artifacts are frequently encountered in phase resolved imaging and sensing techniques based on interferometry. When the value of the actual phase ( φ ) ranges beyond ( - π, π], the extracted phase value (wrapped phase ψ ) is artificially increased or decreased by a multiple of 2π. In this study, we develop a 3D phase unwrapping method that exploits the correlation of 3D phase data ( φ ( x , y , t )) over the other dimension ( t ). We validate our 3D unwrapping method using simulated data, as well as experimental data obtained by optically computed phase microscopy (OCPM) recently developed in our lab. Our result s show that the 3D phase unwrapping method achieves accurate and robust reconstruction of phase φ ( x , y , t ). The application of the 3D phase unwrapping method is not limited to OCPM. Instead, it is a generic approach that can be used for other phase imaging modalities. ( Read Full Article )

MEMS-VCSEL swept-source optical coherence tomography for multi-MHz endoscopic …

Swept-source optical coherence tomography (SS-OCT) enables volumetric imaging of subsurface structure, but applications requiring wide fields of view, rapid imaging, and higher resolutions have been challenging because of the need for multi-MHz A-scan rates. Until now, achieving multi-MHz A-scan rates has been limited to Fourier-domain mode-locked lasers or stretched-pulse lasers. We describe a microelectromechanical-system, vertical-cavity surface-emitting laser (MEMS-VCSEL) for SS-OCT at A-scan rates of 2.4 and 3.0 MHz using a dual-channel acquisition system. Dual-channel operation enables simultaneous acquisition of Mach-Zehnder interferometer (MZI) fringes for sweep-to-sweep calibration and resampling, overcoming inherent optical clock limitations in state-of-the-art digitizers. We demonstrate structural OCT and OCT angiography (OCTA) imaging of the swine gastrointestinal tract using a suite of endoscopic devices, including a 3.2 mm diameter micromotor catheter, a 12 mm diameter...

Cascade Optical Coherence Tomography (C-OCT) for Surface Form Metrology of – ProQuest

Freeform optical components enable dramatic advances in optical system performance and packaging. As the saying goes, “one cannot make what one cannot measure.” Surface form metrology of as-built freeform optics remains a challenge and an active area of research. In this dissertation, a novel cascade optical coherence tomography (C-OCT) technique was conceived towards addressing this metrology challenge. The C-OCT theoretical framework was developed, and a metrology system was built to demonstrate its working principle and metrology capability experimentally. Three significant areas were investigated to realize a C-OCT metrology system with nanometer-level measurement uncertainty. First, the sample arm requirements concerning telecentricity, distortion mapping, residual wavefront error, and image plane flatness were explicitly addressed. Signal throughput was also discussed, which led to the conception of a pseudo-bistatic configuration. Two custom objective lenses were ...

Reflectance-Based Structural Quantification of the Healthy and Glaucomatous Retinal Nerve …

Glaucoma is a group of progressive optic neuropathies that can lead to irreversible vision loss if left untreated. Spectral-domain optical coherence tomography (SD-OCT) is an important imaging tool used in the diagnosis and management of glaucoma. It provides thickness measurements of the retinal nerve fiber layer (RNFL), a useful index for monitoring progressive thinning that occurs from damage. However, there exists high between-subject variability in RNFL thickness in people free of eye disease. Another approach is RNFL reflectance, proposed in 1921 when reduction in reflectance was observed in damaged RNFL. Despite numerous reports from the past century supporting this, clinically applied quantification of RNFL reflectance using OCT is possible but lacking. First, I assessed healthy and glaucomatous eyes for the presence of presumed activated astrocytes and Müller cells (ARAM), a superficial retinal gliosis that could complicate reflectance-based measurements of the RNFL an...

Applications of Visible-Light Optical Coherence Tomography in the Eye and Brain –

Optical coherence tomography (OCT) is a non-invasive, label-free technology that can image biological tissues in vivo with micrometer-scale resolution. Since its development in 1991, OCT has been successfully commercialized and widely adopted in the clinic for the diagnosis and monitoring of retinal diseases. A typical commercial OCT system may have an axial resolution of 5-10 micrometers. By shortening the wavelength range of the light source, visible-light OCT (vis-OCT) enables an improved axial resolution of 1-micrometer, improved tissue scattering contrasts, and additional functional information. The bulk of this dissertation focuses on vis-OCT imaging of the Schlemm’s canal and limbal vascular network in mice in vivo. To this end, necessary system modifications, experimental methods, and image processing algorithms are presented. The size of the Schlemm’s canal in response to IOP changes and the presence of blood reflux was quantified. A machine learning model was d...

The Advanced Applications for Optical Coherence Tomography in Skin Imaging (Thesis)

Optical coherence tomography (OCT), based on low coherent interferometry, is an FDAapproved non-invasive imaging modality. It uses a low coherent near-infrared laser around the wavelength of 1300 nm [1]. OCT has been widely used in ophthalmology to assess retina thickness and anatomical changes. In 1997, this technology was tested to image the cross-section of human skin in vivo, and it was able to visualize different skin layers and skin appendages [2]. Although, OCT has great potential in monitoring skin morphologic changes, skin cancer diagnosis, and tumor margin assessment [3], it is not well recognized and adopted by many dermatologists. Therefore, in this research work, we aim to explore the potential clinical applications of OCT in dermatology, especially focused on melanoma detection. We began with a brief introduction of OCT and an overview of melanoma diagnosis in the clinic. We also discussed the application of different imaging modalities to assist melanoma detection. OC...

Polarization-Sensitive Optical Coherence Tomography to Study Diffusion of Plasmonic Gold Nanorods—a Novel Tool for Optical Bioimaging

Optical Coherence Tomography (OCT) is an imaging tool that performs micronresolution, non-invasive, cross-sectional imaging by measuring the echoes of backscattered light. In this thesis, a custom-designed polarization-sensitive OCT (PS-OCT) system is discussed, which is implemented in using plasmonic gold nanorods (GNRs) as diffusion probes. PS-OCT imaging is undertaken in Newtonian fluids and validation of rotational and translational diffusion of GNRs with the Stokes-Einstein relation is presented via analysis of the autocorrelations of the OCT signals. Diffusion of GNRs in non-Newtonian fluids is also studied and the frequency-dependent viscoelasticity is also explored using generalized Stokes-Einstein relation. Furthermore, diffusion of GNRs in the “correlation length ≥ probe” regime is discussed in low concentration polymer solutions. Biological samples such as porous extracellular matrix (ECM) and in vitro mucus are explored using PEGylated GNRs as diffusion pr...

Advances in Optical Coherence Tomography for Retinal Oximetry and Angiography (Thesis)

Optical coherence tomography (OCT) is a high-resolution, non-contact, three-dimensional imaging technique, which has revolutionized the diagnosis and treatment of retinal diseases. Visible-light OCT (vis-OCT) extends OCT by enabling retinal oximetry – the measurement of oxygen saturation of hemoglobin from within individual retinal blood vessels. Three advances in the vis-OCT technique are presented: an improved vis-OCT oximetry method based on circumpapillary scan and graph-search segmentation; the calibration, simulation, and correction of spectroscopic sensitivity rolloff for vis-OCT oximetry; and the measurement of the inner retinal oxygen metabolism in the 50/10 oxygen-induced retinopathy model, an animal model for human retinopathy of prematurity. Optical coherence tomography angiography (OCTA) is another functional extension of OCT, which provides three-dimensional, non-invasive, capillary-level mapping of vascular perfusion. Two studies of OCTA in animal models are des...

The Advanced Applications for Optical Coherence Tomography in Skin Imaging (Thesis)

I NTRODUCTION Optical coherence tomography (OCT), based on low coherent interferometry, is an FDA - approved non - invasive imaging modality. It uses a low coherent near - infrared laser around the wavelength of 1300 nm [1] . OCT has been widely used in ophthalmology to assess r etina thickness and anatomical changes. In 1997, this technology was tested to image the cross - section of human skin in vivo , and it was able to visuali ze different skin layer s and skin appendages [2] . Although , OCT has great potential in monitoring skin morphologic changes, skin cancer diagnosis , and tumor margin assessment [3] , i t is not well recognized and adopted by many dermatologists. Therefore, in this research work, we aim to explore the potential clinical applications of OCT in dermatology, especially focused on melanoma detection. We began with a brief introduction of OCT and an overview of melanoma diagnosis in the clinic. We also discussed the application of different imaging modalities...

Comparing different methods to measure biofilm thickness: the techniques are: optical coherence tomography, confocal laser scanning microscopy and low load compression test (Thesis)

Biofilm formation remains a serious concern in industry and in the medical field. They are responsible for huge economical losses in many industrial sectors and for serious infections associated with biomaterial implants and medical devices. These infections are hard to treat because bacteria within the biofilm are more resistant to antibiotics and to the host immune system. Therefore, studying biofilm properties and mechanisms is of utmost relevance to develop efficient approaches to deal with this drawback. Biofilm thickness is an important parameter in biofilm characterization. The main purpose of this thesis was to assess the suitability of Optical Coherence Tomography (OCT) to measure biofilm thickness by comparing the results with the values obtained with the Low Load Compression Test (LLCT) and Confocal Laser Scanning Microscopy (CLSM). OCT is a nondestructive technique, which is increasingly applied on the medical field and allows the acquisition of images in real-time, in s...

COMPUTATIONAL IMAGING AS APPLIED TO CORONARY ARTERY OPTICAL COHERENCE TOMOGRAPHY

Patients with inadequate stent expansion are at high risk for adverse outcomes, including stent thrombosis as well as in-stent restenosis. Both are well-described complication usually causing acute coronary syndromes and, in the worst-case scenario, sudden cardiac death. Once a stent is deployed in atherosclerotic tissue that is highly resistant to dilation, it is often tricky to fully expand the implanted stent, even using a noncompliant balloon. Careful evaluation of these risks prior to the intervention will aid treatment planning, including potential application of a plaque modification strategy. Moderate to severe calcification in the treated vessel restrict full deployment of a stent. Intravascular optical coherence tomography (IVOCT) is a useful tool to identify calcification lesion severity, reference vessel size, lesion length, and extent of calcification for PCI planning. In addition, IVOCT imaging provides detailed evaluation of stent deployment including areas, stent exp...

Categories

Organizations in the News

OCT Companies in the News

Picture Gallery