Multi-beam miniaturized volumetric scanning microscopy with a single 1-dimensional actuation

Miniaturized optical imaging systems often use a 2-dimensional (2-D) actuator such as a piezoelectric tube or microelectromechanical system actuator for the acquisition of 2-D and higher dimensional images over an areal field of view (FOV). Piezoelectric tubes are the most compact, but usually produce impractical sub-millimetre FOVs and are difficult to fabricate at scale, leading to high costs. Planar piezoelectric bending actuators ('benders') are substantially lower cost and capable of much larger actuations, albeit 1-dimensional (1-D) and traditionally inadequate for 2-D steering tasks. We present a piezoelectric bender imaging system that exploits mechanical motion coupling to produce multi-millimetre scale 2-D scan coverage. Leveraging optical coherence tomography with a long coherence length laser, we further extend the FOV using three depth-multiplexed imaging beams from optical fibres resonating in synchronicity across the width of the bender. Each fibre had a FOV of ~2.1 x 1.5 mm, contributing to a stitched field of ~2.1 x 2.9 mm with a beam resolution of 12.6 um full-width at half-maximum. Imaging of biological samples including stomach tissue, an ant and cell spheroids was performed. This multi-fold improvement in imaging coverage and cost-effectiveness promises to accelerate the advent of piezoelectric scanning in compact devices such as endoscopes for biomedicine, and headsets for augmented/virtual reality and neuroscience

LiDAR-NeRF: Novel LiDAR View Synthesis via Neural Radiance Fields

We introduce a new task, novel view synthesis for LiDAR sensors. While traditional model-based LiDAR simulators with style-transfer neural networks can be applied to render novel views, they fall short of producing accurate and realistic LiDAR patterns because the renderers rely on explicit 3D reconstruction and exploit game engines, that ignore important attributes of LiDAR points. We address this challenge by formulating, to the best of our knowledge, the first differentiable end-to-end LiDAR rendering framework, LiDAR-NeRF, leveraging a neural radiance field (NeRF) to facilitate the joint learning of geometry and the attributes of 3D points. However, simply employing NeRF cannot achieve satisfactory results, as it only focuses on learning individual pixels while ignoring local information, especially at low texture areas, resulting in poor geometry. To this end, we have taken steps to address this issue by introducing a structural regularization method to preserve local structural details. To evaluate the effectiveness of our approach, we establish an object-centric multi-view LiDAR dataset, dubbed NeRF-MVL. It contains observations of objects from 9 categories seen from 360-degree viewpoints captured with multiple LiDAR sensors. Our extensive experiments on the scene-level KITTI-360 dataset, and on our object-level NeRF-MVL show that our LiDAR-NeRF surpasses the model-based algorithms significantly.Comment: This paper introduces a new task of novel LiDAR view synthesis, and proposes a differentiable framework called LiDAR-NeRF with a structural regularization, as well as an object-centric multi-view LiDAR dataset called NeRF-MV

Correction of rotational distortion for catheter-based en face OCT and OCT angiography

We demonstrate a computationally efficient method for correcting the nonuniform rotational distortion (NURD) in catheter-based imaging systems to improve endoscopic en face optical coherence tomography (OCT) and OCT angiography. The method performs nonrigid registration using fiducial markers on the catheter to correct rotational speed variations. Algorithm performance is investigated with an ultrahigh-speed endoscopic OCT system and micromotor catheter. Scan nonuniformity is quantitatively characterized, and artifacts from rotational speed variations are significantly reduced. Furthermore, we present endoscopic en face OCT and OCT angiography images of human gastrointestinal tract in vivo to demonstrate the image quality improvement using the correction algorithm.National Institutes of Health (U.S.) (R01-EY011289-26)National Institutes of Health (U.S.) (R44-EY022864-01)National Institutes of Health (U.S.) (R01-CA075289-16)National Institutes of Health (U.S.) (R44-CA101067-05)National Institutes of Health (U.S.) (R01-CA178636-02)United States. Air Force Office of Scientific Research (Contract FA9550-10-1-0063)United States. Air Force Office of Scientific Research (Contract FA9550-12-1-0499

Computer-Aided Analysis of Gland-Like Subsurface Hyposcattering Structures in Barrett’s Esophagus Using Optical Coherence Tomography

(1) Background: Barrett's esophagus (BE) is a complication of chronic gastroesophageal reflux disease and is a precursor to esophageal adenocarcinoma. The clinical implication of subsurface glandular structures of Barrett's esophagus is not well understood. Optical coherence tomography (OCT), also known as volumetric laser endomicroscopy (VLE), can assess subsurface glandular structures, which appear as subsurface hyposcattering structures (SHSs). The aim of this study is to develop a computer-aided algorithm and apply it to investigate the characteristics of SHSs in BE using clinical VLE data; (2) Methods: SHSs were identified with an initial detection followed by machine learning. Comprehensive SHS characteristics including the number, volume, depth, size and shape were quantified. Clinical VLE datasets collected from 35 patients with a history of dysplasia undergoing BE surveillance were analyzed to study the general SHS distribution and characteristics in BE. A subset of radiofrequency ablation (RFA) patient data were further analyzed to investigate the pre-RFA SHS characteristics and post-RFA treatment response; (3) Results: SHSs in the BE region were significantly shallower, more vertical, less eccentric, and more regular, as compared with squamous SHSs. SHSs in the BE region which became neosquamous epithelium after RFA were shallower than those in the regions that remained BE. Pre-ablation squamous SHSs with higher eccentricity correlated strongly with larger reduction of post-ablation BE length for less elderly patients; (4) Conclusions: The computer algorithm is potentially a valuable tool for studying the roles of SHSs in BE. Keywords: Barrett;s esophagus; glands; optical coherence tomographyNational Institutes of Health (U.S.) (Grant R01-CA075289-19)National Institutes of Health (U.S.) (Grant RO1-CA178636-04)National Institutes of Health (U.S.) (Grant R01-EY011289-30)United States. Air Force Office of Scientific Research (Contract FA9550-12-1-0551)United States. Air Force Office of Scientific Research (Contract FA9550-15-1-0473

Three-Dimensional Ultrasound Guidance of Autonomous Robotic Breast Biopsy: Feasibility Study

Feasibility studies of autonomous robot biopsies in tissue have been conducted using real time 3D ultrasound combined with simple thresholding algorithms. The robot first autonomously processed 3D image volumes received from the ultrasound scanner to locate a metal rod target embedded in turkey breast tissue simulating a calcification, and in a separate experiment, the center of a water-filled void in the breast tissue simulating a cyst. In both experiments the robot then directed a needle to the desired target, with no user input required. Separate needle-touch experiments performed by the image-guided robot in a water tank yielded an rms error of 1.15 mm

Ultrahigh speed endoscopic swept source optical coherence tomography using a VCSEL light source and micromotor catheter

We developed an ultrahigh speed endoscopic swept source optical coherence tomography (OCT) system for clinical gastroenterology using a vertical-cavity surface-emitting laser (VCSEL) and micromotor based imaging catheter, which provided an imaging speed of 600 kHz axial scan rate and 8 μm axial resolution in tissue. The micromotor catheter was 3.2 mm in diameter and could be introduced through the 3.7 mm accessory port of an endoscope. Imaging was performed at 400 frames per second with an 8 μm spot size using a pullback to generate volumetric data over 16 mm with a pixel spacing of 5 μm in the longitudinal direction. Three-dimensional OCT (3D-OCT) imaging was performed in patients with a cross section of pathologies undergoing standard upper and lower endoscopy at the Veterans Affairs Boston Healthcare System (VABHS). Patients with Barrett’s esophagus, dysplasia, and inflammatory bowel disease were imaged. The use of distally actuated imaging catheters allowed OCT imaging with more flexibility such as volumetric imaging in the terminal ileum and the assessment of the hiatal hernia using retroflex imaging. The high rotational stability of the micromotor enabled 3D volumetric imaging with micron scale volumetric accuracy for both en face and cross-sectional imaging. The ability to perform 3D OCT imaging in the GI tract with microscopic accuracy should enable a wide range of studies to investigate the ability of OCT to detect pathology as well as assess treatment response.National Institutes of Health (U.S.) (R44EY022864-01)National Institutes of Health (U.S.) (R01-CA75289-17)National Institutes of Health (U.S.) (R44-CA101067-06)National Institutes of Health (U.S.) ( R01-EY011289-27)National Institutes of Health (U.S.) (R01-HL095717-04)National Institutes of Health (U.S.) (R01-NS057476-05)United States. Air Force Office of Scientific Research (FA9550-10-1-0063)United States. Air Force Office of Scientific Research. Medical Free Electron Laser Program (FA9550-10-1-0551)German Research Foundation (DFG-GSC80-SAOT)German Research Foundation (DFG-HO-1791/11-1)Center for Integration of Medicine and Innovative Technolog

Development and investigation of devices for ultrahigh speed gastrointestinal Optical Coherence Tomography imaging

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.Includes bibliographical references (pages 139-149).Diseases of the gastrointestinal (GI) tract are typically diagnosed by random biopsy of tissue, which samples only a small area and often misses focal neoplasias. Existing endoscopic visualization tools including white light endoscopy, narrowband imaging and confocal laser endomicroscopy have enabled in vivo assessment to guide biopsies, but suffer from technical limitations and have demonstrated suboptimal sensitivity and specificity to neoplasia. Optical Coherence Tomography (OCT) can generate in vivo, 3-dimensional microscopic imaging. Recent efforts in ultrahigh-speed OCT systems for endoscopic applications have shown promise, but devices had limited fields of view and imprecise beam scanning mechanisms, limiting image quality and coverage. This thesis develops a wide range of new fiber optic devices that substantially extend OCT capabilities in the GI tract, either by greatly increasing field of view for wide field mapping of entire luminal organs, or achieving high precision 2-D beam scanning with compact actuators for in vivo microscopy. Piezoelectrically actuated fiber scanning devices enable forward viewing for focal inspection, while micromotor actuators combined with pneumatic or piezoelectric mechanisms enclosed in tethered capsules generate side viewing over large areas. The work also advances the emerging paradigm of gastrointestinal screening without use of sedation, which promises to lower costs of screening and improve access for a broader population. Design, fabrication and benchtop evaluation of devices, as well as pre-clinical and clinical imaging protocols are reported. Results from validation studies in living swine, and human patients in collaboration with the Veterans Affairs Boston Healthcare System are discussed. The thesis work demonstrates new imaging modalities for in vivo detection and diagnosis of GI pathology that could have important applications in disease screening, surveillance, and therapeutic procedures.by Kaicheng Liang.Ph. D

Forward viewing Fourier-domain optical coherence tomography (FDOCT) endomicroscopy.

Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014."February 2014." Cataloged from PDF version of thesis.Includes bibliographical references (pages 60-69).A forward viewing fiber optic-based imaging probe device was designed and constructed for use with ultrahigh speed optical coherence tomography in the human gastrointestinal tract. The light source was a MEMS-VCSEL at 1300 nm wavelength running at 300 kHz sweep rate, giving an effective A-line rate of 600 kHz. Data was acquired with a 1.8 GS/s A/D card optically clocked by a maximum fringe frequency of 1 GHz. The optical beam from the probe was scanned by a freely deflecting optical fiber that was mounted proximally on a piezoelectric tubular actuator, which was electrically driven in two perpendicular dimensions to produce a spiral scan pattern. The probe has a 3.3 mm outer diameter and is intended for endoscopic imaging. Multiple optical systems were designed to enable microscopic imaging at variable fields. The probe could also be electrically zoomed by tuning the driving voltage to the piezoelectric actuator, reducing the deflection range of the scanning fiber and thus the scanned field. The optical and mechanical design of the probe was optimized for both axial and transverse compactness.by Kaicheng Liang.S.M

Land Use Conflict Changes and Driving Forces of Beibu Gulf Economic Zone

Based on PSR model, it built an indicator evaluation system for land use conflicts of Beibu Gulf Economic Zone in 2003-2011. Then, it made an analysis of driving forces of land use conflicts using principal components analysis (PCA) method. Results indicate that land use conflicts take on increasing trend and the trend becomes more apparent since 2009, and Nanning has the highest conflict index; driving forces of land use conflicts mainly include population, social and economic development, agricultural input, ecological protection, and land use policies