Micro-electro-mechanical system (MEMS) scanner has the potential to be used in the optical coherence tomography (OCT) imaging system due to fabrication friendliness, and miniature architecture size. The function of feedback control circuits provides the output signal to be fed back to the scanner enabling correcting the drive waveform in real-time to conquer the limitation of scanning stability of the MEMS scanner. In this study, we have developed a swept-source optical coherence tomography (SS-OCT) system configuration of a dual-axis MEMS scanner, switchable operated between open-loop and closed-loop driving modes, to investigate the scanning stability of the MEMS scanner by analyzing the scanning trajectories detected by the position sensitive device (PSD) sensor at frame rates of 50 and 250 Hz. Preliminary results of the quantitative analysis are presented in this paper.
We have developed a multifunctional catheter-based OCT system, which provides architecture and birefringence information of biological tissue and allows volumetric imaging of the luminal part of the cervix. Preliminary imaging results of the in vivo human buccal mucosa and tongue were shown to validate the capabilities of volumetric imaging in the developed multifunctional OCT system, and further obtained the birefringence information by analyzing the polarization information of the OCT signal to implement the multifunctional OCT imaging.
Optical Coherence Tomography (OCT) has been widely used in many clinical apartments. The trade-off between Field-of-View (FOV) and transverse resolution has always become critical. High-Resolution (HR) image reconstruction of OCT has the potential to increase the resolution without reducing the FOV. Although it has been widely explored in these years, it is hard to find one-to-one paired high-resolution for reference. The SR methods are used to improve the cross-sectional OCT image only. Therefore, we build a custom-design, wide field-of-view, multi-scale optical coherence tomography that can allow us to produce excellent high- and low-resolution one-to-one mapping volumetric data set. With the SR methods, we can reduce the acquisition of synthetic high-resolution volumetric images by up to four times.
Polarization-sensitive optical coherence tomography (PS-OCT) is a non-destructive and three-dimensional imaging technique that can provide polarization properties, e.g., phase retardation and the optical axis, as well as architectural information similar to conventional OCT from the sample. In this study, we have developed a high-speed PS-OCT imaging engine by using a novel wavelength-swept laser light source based on a high-contrast grating vertical-cavity surface-emitting laser (HCG-VCSEL). Example PS-OCT imaging including the human fingernail junction, 3D plastic printing material, and the chicken breast tissue demonstrated the depth-resolved measurement of the multifunctional information of the sample with PS-OCT and HCG-VCSEL light source at an A-scan rate of 250 kHz.
Several optical technologies have been demonstrated as potential diagnostic tools for skin imaging, such as reflectance confocal microscopy (RCM) and optical coherence tomography (OCT). Although RCM could support cellular-level imaging, OCT could provide a larger field of view and a longer imaging depth than RCM. To quantitatively evaluate the skin condition with OCT, it is essential to develop an algorithm extracting different features, for example, the epidermis thickness and the optical characteristic of the epidermis. Although various segmentation algorithms have been proposed, most of the golden standards used involve the delineation of the boundary manually, where the labeling is highly relied on clinicians' experience and might vary among different physicians and the physician him or herself. Therefore, in this study, we collected skin OCT images of different sites from 20 subjects using a portable spectral-domain OCT system. The contrast of the OCT images can be effectively improved by optical attenuation coefficient (OAC) computation. This enables the development of a fully automatic segmentation algorithm, providing the parameters such as the (i) epidermis thickness and the (ii, iii) roughness of the boundary between the epidermis and air as well as the epidermis and dermis. Also, the (iv, v) OAC coefficients of the epidermis and upper dermis layer are available. Collectively, the developed algorithm supports the quantitative analysis of the five parameters across the imaging site with volumetric OCT imaging. We believe the developed algorithm can facilitate the implementation of skin OCT imaging for aesthetic medicine as a modality for objective pre- and post-treatment evaluation.
We present a high-speed swept-source optical coherence tomography (SS-OCT) imaging system using an electrically pumped, micro-electromechanical-system (MEMS) tunable HCG-VCSEL operating at the 1060 nm wavelength regime. Comparing to existing MEMS VCSEL light sources for SS-OCT, a movable high-contrast grating (HCG) is used as the top mirror of the laser cavity, replacing the conventional distributed Bragg reflector mirror design. By applying a reverse bias voltage, the HCG mirror actuates downward toward the VCSEL cavity, changing the effective cavity length and resulting in wavelength tuning responses. The developed SS-OCT system allows an A-scan rate of 250 kHz, a detection sensitivity of 98 dB, and an axial imaging resolution of 22 µm (full-width at half-maximum (FWHM), in air). The A-scan rate can be further improved to 500 kHz if both the backward (long to short wavelength) and forward laser sweep are used. In the experimental setup, a dual-channel acquisition scheme was utilized to provide calibration of the OCT signal with a separate calibration interferometer. Volumetric imaging of the human fingernail/nail fold junction in vivo shows the feasibility of providing high-speed imaging of the tissue architectures. The MEMS tunable HCG-VCSEL light source can provide high-speed OCT imaging with a more compact light source footprint and potentially a lower cost
In this study, we have developed a small-footprint imaging framework identifying changes in the microvasculature of the mouse brain at different physiological states, including anesthesia, waking, and movement with the OCT angiography technique.
Recently, the functional extension of optical coherence tomography (OCT) with OCT angiography (OCTA) allows
volumetric imaging of the subsurface microvasculature without requiring exogenous contrast agents like conventional
angiography techniques. However, performing OCTA requires intensive computation to extract the changes of OCT
signal due to moving red blood cells in the microvascular network. In this study, we have developed a graphic processing
unit (GPU)-accelerated framework to realize high speed OCTA imaging and the visualization of the microvascular
network after the data acquisition. In addition, we investigate the feasibility of providing real-time microvascular imaging
leveraging dynamic scattering OCT and GPU.
Due to the complex geometry of the oral cavity, it is challenging to perform wide-field optical coherence tomography
(OCT) imaging of different regions of the oral mucosa, particularly in patients with opening difficulty due to submucosa
fibrosis. In addition to changes in the tissue architectures, angiogenesis has been demonstrated to play an important role in
the progression of oral neoplasm. In this study, we have developed a micromotor imaging catheter allowing high-speed
and wide-field OCT and OCT angiography imaging of the oral mucosa. Leveraging polarization diversity detection, it
ensures an optimal detection of the OCT signal for the entire circumference.
Optical coherence tomography (OCT) is non-invasive biomedical imaging technique, which can provide volumetric imaging of the tissue architectural information. In this talk, I will briefly discuss the preliminary results of several ongoing works in my lab, including the quantitative analysis of the microvasculature with the animal model and investigation of the mouse cochlear anatomy.
Living cell culture provides convenient and standard biotechnology chosen option in the laboratory. However, current imaging methods could not present real 3D models. Therefore, we have developed a compact, high-speed spectral-domain optical coherence microscopy (SD-OCM) system to observe the interaction of the tumor cell spheroid with gold nanoparticles. Volumetric OCM images of the cell spheroid were acquired using an in-house C++ interface and used a low-cost microcontroller for triggering to synchronize the galvanometer mirror to the detector array. We designed a hermetic chamber on the microscope stage to control temperature, humidity, CO2 concentration in the experiment.
Oral cancer was ranked as the fifth most common cancers in both sexes in Taiwan in 2014. For patients diagnosed with the advanced or late stage of oral SCC, the five-year survival rate is reported to be ~ 33% suggesting the importance of the early detection of oral cancer. There have been various studies of investigating the clinical utility of OCT for the early detection of oral precancerous lesions with 1300 nm OCT technology. In this study, we have developed a long-wavelength, multiscale OCT imaging system enabling multiscale imaging of the ex vivo oral precancerous tissue with an increased imaging depth. Objectives with two different magnifications are mounted to a power turret, enabling seamless change of the OCT imaging resolution via the software control. OCT imaging over a variety of oral precancer pathologies will be demonstrated with above OCT system.
The inner ear is a small and sophisticated organ, mainly comprising of the vestibular system and cochlea, responsible for hearing function and plays a crucial role in the life wellness.There have been several studies of investigating the cochlear structures with OCT, and most of these studies used OCT systems with a central wavelength of 1.3 µm. However, the utility of 1 µm OCT system for cochlear imaging application has yet been explored albeit the capability of providing OCT images with a higher axial resolution. Therefore, in this study, we have developed a 1.3 µm and a 1 µm OCT system allowing quantitative and spectroscopic comparison of the cochlear microstructures.
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