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.
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.
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
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.
Serving as minimally invasive surgery, robotic surgery has become a promising treatment approach toward various
diseases, such as Urology, Gastroenterology, or Gynecology. Although robotic surgery exhibits several advantages of
decreasing the incision size and shorter patient stay, it still imposes extensive labor loading to the surgeons. Therefore,
recently, semiautonomous laparoscope surgery has been emerged to improve the surgery precision further. In this study,
we have developed a miniature imaging head combing wide-angle camera and optical coherence tomography aiming for
semiautonomous laparoscope surgery. Leveraging the ranging information provided from OCT, it allows more agile
control of the imaging head.
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.
The nail provides a functional protection to the fingertips and surrounding tissue from external injuries. Nail plate divided into three layers including dorsal, intermediate, and ventral layers. The dorsal layer consists of compact, hard keratins, limiting topical drug delivery through the nail. In this study, we investigate the application of fractional CO2 laser that produces arrays of microthermal ablation zones (MAZs) to facilitate drug delivery in the nails. Moreover, optical coherence tomography (OCT) is implemented for real-time monitoring of the laser–skin tissue interaction, sparing the patient from invasive surgical sampling procedure. Observations of drug diffusion through the induced MAZ array are achieved by evaluating the time-dependent OCT intensity variance. Subsequently, nails are treated with cream and liquid topical drugs to investigate the feasibility and diffusion efficacy of laser-assisted drug delivery. Our results show that fractional CO2 laser improves the efficacy of topical drug delivery in the nail plate, and that OCT could potentially be used for in vivo monitoring of the depth of laser penetration as well as real-time observations of drug delivery.
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