Sensorineural hearing loss (SNHL) is the most common sensory problem that causes permanent hearing loss due to the damage of cochlear hair cells. Current clinical imaging techniques do not provide sufficient resolution and functional assessment of the intracochlear structures. We developed a dual-mode endoscopic system that combines optical coherence tomography and autofluorescence to visualize the morphology and biochemical changes of the intracochlear structures. The preclinical assessment of the system was performed in a ovine model of SNHL in vivo. The preliminary results suggest that this approach may provide more accurate diagnosis of cochlear pathology and enable targeted SNHL therapies.
We report the development and the pre-clinical testing of a manual scanning OCT-based probe for core needle biopsy guidance. While stereotactic radiography, ultrasound, computed tomography, and magnetic resonance imaging are used to guide needle placement within a tumor, the optical probe provides the radiologist with the capability to examine tissue cellularity at the tip of the biopsy needle. The capability to investigate tissue cellularity prior to taking the biopsy could help reduce the number of non-diagnostic biopsies and increase the amount of viable tumor tissue within the biopsy core. This last aspect is very important in the new era of personalized cancer therapy, because greater tissue quantity is needed for various biomarker assays. This technology has been evaluated by us on a rabbit model of soft tissue cancer. Our results indicate the capability of this OCT-based probe for determining the in situ cellularity of the tissue at the tip of the biopsy needle.
Identification of positive margins during breast cancer conserving surgery is crucial for successful tumor resection. To address this clinical need, we developed a microscope that combines fluorescent microscopy, optical coherence tomography (OCT), and reflectance confocal microscopy (RCM) to identify the presence of positive tumor margins in surgical specimens. A cancer-targeting fluorescent agent is used to highlight potentially positive margins and guide combined RCM/OCT imaging. Combined RCM/OCT is used to accurately determine the extent of the positive margins, aided by custom image-processing techniques. This instrument has the potential to provide tumor margin guidance in the surgical suite, reducing reliance on lengthy histopathological inquiry and reducing the need for repeated surgery.
In the current era of personalized cancer therapy, various drugs need to be rapidly tested to determine their efficacy in killing cancer cells. In this way, the most effective drug can be administered to improve therapy effectiveness. However, since the biopsy specimens are heterogeneous, efficient testing requires the use only of the viable tumor part of the specimen. Therefore, rapid and automated evaluation of specimen heterogeneity is needed. In this paper presents an automated algorithm for tissue heterogeneity estimation based on OCT images. This algorithm use image texture features to differentiate between healthy and cancer tissue.
KEYWORDS: Ear, Optical coherence tomography, Endoscopy, Auto-fluorescence imaging, In vivo imaging, Magnetic resonance imaging, Pathology, Visualization, Sensors, Bone
This study presents a novel technology for in vivo cochlear imaging in sensorineural hearing loss (SNHL). SNHL is the most common type of permanent hearing loss and is associated with damaged hair cells of the cochlea. State of the art clinical imaging does not have sufficient resolution to show inner ear microstructure. We are developing and testing a dual-modal endoscopic instrument that combines optical coherence tomography (OCT) and autofluorescence imaging (AFI) for dynamic cochlear imaging. If successful, this approach will improve our understanding of the cellular basis of SNHL and enable the development of targeted therapies for inner ear disorders.
We demonstrate optical biopsy of vocal folds to assess its surface and subsurface movement during phonation on ex-vivo calf larynx using parallel OCT (POCT). In this technique, we will enable simultaneous interrogation of multiple locations along the vocal fold, there by eliminating motion-blur artifacts exhibited by the sequential sampling provided by conventional flying-spot OCT. Currently, in voice clinics, laryngologists and speech-language pathologists rely heavily on Video Stroboscopy (VS) coupling with, visual judgments of vocal fold morphology and auditory perceptions of voice quality, to make effective diagnostic, surgical and therapeutic decisions. There is a constant need of an endoscopic imaging tool in voice clinics that can directly capture the three-dimensional (3D) surface motion of the vocal folds in real time as patients phonate. To address the need, we will present a POCT/VS imager that will combine parallel swept source OCT technique with VS to provide a real time display of the vocal folds in all three axial dimensions during phonation. The results will yield cross sections (B-Scans) with ~16 co-linear sampling locations spread over ~5mm on a phonating ex-vivo calf larynx showing fluid periodic cyclic motion of the vocal folds (~A-scan rate) in real time enabled by POCT approach. We will also capture VS images in sync with POCT B-scans validating the real time cross sectional probing of POCT/VS imager.
In this paper, we summarize our recent advances in the development and pre-clinical testing of the 2-nd generation OCT-based probe for core needle biopsy guidance. The acquired OCT images are processed in real-time in a GPU unit to provide the interventional radiologist with the capability to examine the tissue cellularity at the tip of the biopsy needle before deciding to take a biopsy core. The extensive testing of this technology on a rabbit model of soft tissue cancer is discussed in detail. The pre-clinical results demonstrate the capability of this OCT-based probe for determining the in situ cellularity of the tissue at the tip of the biopsy needle and thus its potential use for improving the quality of the sampled biopsy cores.
In this paper we summarize our recent advances in the development of a combined optical coherence tomography (OCT)/ reflectance confocal microscopy (RCM) approach for diagnosing non-melanoma skin cancers and guiding laser ablation therapy. After developing and clinically demonstrating a hand-held probe [1], our current focus is in adding the capability for generating rapid mosaic images of large areas of the skin (~15 mm x 15mm), as well as on developing a post-processing software that allows for rapid 3-D rendering of the collected data. We are also developing an automated segmentation algorithm that might be used to more objectively assess the depth of the non-melanoma tumors. With these capabilities, our integrated RCM and OCT imaging approach will provide 3-D microscopic views in orthogonally oriented and enfaceoriented planes with a range of resolutions and fields of view, which should further advance optical imaging to noninvasively guide both diagnosis as well as therapy of non-melanoma skin cancers.
[1]. N. Iftimia et al., Handheld optical coherence tomography–reflectance confocal microscopy probe for detection of basal cell carcinoma and delineation of margins. J. Biomed. Opt. 22(7), 076006
KEYWORDS: Optical coherence tomography, Reflectivity, Confocal microscopy, Skin, Tumors, In vivo imaging, Spectroscopy, 3D image processing, 3D displays
We present a hand-held implementation and preliminary evaluation of a combined optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) probe for detecting and delineating the margins of basal cell carcinomas (BCCs) in human skin in vivo. A standard OCT approach (spectrometer-based) with a central wavelength of 1310 nm and 0.11 numerical aperture (NA) was combined with a standard RCM approach (830-nm wavelength and 0.9 NA) into a common path hand-held probe. Cross-sectional OCT images and enface RCM images are simultaneously displayed, allowing for three-dimensional microscopic assessment of tumor morphology in real time. Depending on the subtype and depth of the BCC tumor and surrounding skin conditions, OCT and RCM imaging are able to complement each other, the strengths of each helping overcome the limitations of the other. Four representative cases are summarized, out of the 15 investigated in a preliminary pilot study, demonstrating how OCT and RCM imaging may be synergistically combined to more accurately detect BCCs and more completely delineate margins. Our preliminary results highlight the potential benefits of combining the two technologies within a single probe to potentially guide diagnosis as well as treatment of BCCs.
A novel multimodal optical imaging approach for real-time assessment of surgical margins on breast cancer lumpectomy specimens is presented. Our approach is to target cancer cells using an optically silent peptide substrate containing two (NIR) fluorochromes, internally quenched, which are cleaved by highly expressed breast cancer enzymes, like urokinase-type plasminogen activator (uPA). Thus this agent becomes highly fluorescent only on the cancer area when the specimen is excited by a NIR laser beam. A fluorescence imager is used to highlight cancer-suspect margins on the surgical specimen, while high-resolution optical coherence tomography (OCT) imaging is used to visualize tissue morphology on the highlighted areas and confirm or rule out cancer presence. This technology will hopefully increase the success rate of cancer surgeries, reduce the risk of cancer recurrence and significantly reduce US healthcare costs.
Sensorineural hearing loss (SNHL), which typically originates in the cochlea, is the most common otologic problem caused by aging and noise trauma. The cochlea, a delicate and complex biological mechanosensory transducer in the inner ear, has been extensively studied with the goal of improving diagnosis of SNHL. However, the difficulty associated with accessing the cochlea and resolving the microstructures that facilitate hearing within it in a minimally-invasive way has prevented us from being able to assess the pathology underlying SNHL in humans. To address this problem we investigated the ability of a multimodal optical system that combines optical coherence tomography (OCT) and single photon autofluorescence imaging (AFI) to enable visualization and evaluation of microstructures in the cochlea. A laboratory OCT/AFI imager was built to acquire high resolution OCT and single photon fluorescence images of the cochlea. The imager’s ability to resolve diagnostically-relevant details was evaluated in ears extracted from normal and noise-exposed mice. A prototype endoscopic OCT/AFI imager was developed based on a double-clad fiber approach. Our measurements show that the multimodal OCT/AFI imager can be used to evaluate structural integrity in the mouse cochlea. Therefore, we believe that this technology is promising as a potential clinical evaluation tool, and as a technique for guiding otologic surgeries such as cochlear implant surgery.
We present a novel method, based on encoder mapping OCT imaging, for real-time guidance of core biopsy procedures. This method provides real-time feedback to the interventional radiologist, such that he/she can reorient the needle during the biopsy and sample the most representative area of the suspicious mass that is being investigated. This aspect is very important for tailoring therapy to the specific cancer based on biomarker analysis, which will become one of the next big advances in our search for the optimal cancer therapy. To enable individualized treatment, the genetic constitution and the DNA repair status in the affected areas is needed for each patient. Thus, representative sampling of the tumor is needed for analyzing various biomarkers, which are used as a tool to personalize cancer therapy. The encoder-based OCT enables samping of large size masses and provides full control on the imaging probe, which is passed through the bore of the biopsy guidance needle. The OCT image is built gradually, based on the feedback of an optical encoder which senses the incremental movement of the needle with a few microns resolution. Tissue mapping is independent of the needle speed, while it is advanced through the tissue. The OCT frame is analyzed in real-time and tissue cellularity is reported in a very simple manner (pie chart). Our preliminary study on a rabbit model of cancer has demonstrated the capability of this technology for accurately differentiating between viable cancer and heterogeneous or necrotic tissue.
We present a novel technology based on a high sensitivity/specificity cancer targeting agent and of a novel fluorescence-guided microscopy (FGM) scheme for intraoperative assessment of surgical margins in breast cancer patients. Cancer cells are targeted using an optically silent peptide substrate coupled to a near infrared
(NIR) fluorochrome that is cleaved by highly mediated breast cancer enzymes, like urokinase-type
plasminogen activator (uPA), to become highly fluorescent when excited by a NIR laser beam. A FGM instrument is used to localize cancer-suspect areas on the lumpectomy specimen and visualize
tissue morphology at the sub-cellular scale, such that a trained pathologist can read these images in
real-time and confirm or rule-out cancer presence. The proposed technology will enable efficient
assessment of surgical specimens during surgery, when it is mostly needed, and therefore help the
clinician to determine if additional tissue excision is needed or not. The preliminary testing of this technology on breast surgical specimens will be discussed.
Most studies evaluating the potential of optical coherence tomography (OCT) for the diagnosis of oral cancer are based on visual assessment of OCT B-scans by trained experts. Human interpretation of the large pool of data acquired by modern high-speed OCT systems, however, can be cumbersome and extremely time consuming. Development of image analysis methods for automated and quantitative OCT image analysis could therefore facilitate the evaluation of such a large volume of data. We report automated algorithms for quantifying structural features that are associated with the malignant transformation of the oral epithelium based on image processing of OCT data. The features extracted from the OCT images were used to design a statistical classification model to perform the automated tissue diagnosis. The sensitivity and specificity of distinguishing malignant lesions from benign lesions were found to be 90.2% and 76.3%, respectively. The results of the study demonstrate the feasibility of using quantitative image analysis algorithms for extracting morphological features from OCT images to perform the automated diagnosis of oral malignancies in a hamster cheek pouch model.
Several factors are spurring the development of hardware and software to accomplish high-speed
processing for Optical Coherence Tomography (OCT). The two most prevalent architectures incorporate
either an FPGA or a GPU. While GPUs have faster clock-speed the fact an FPGA can be pipelined
makes a direct comparison based simply on system specifications difficult. We have undertaken an effort
to make a direct comparison on the same host and consider the total time from digitization to rendering of
the image. In addition to making quantitative comparisons between the two architectures we hope to
derive useful benchmarks that will inform the design of an optimal high-speed processing system.
Clinical diagnosis of cochlear dysfunction typically remains incomplete due to a lack of proper diagnostic methods.
Medical imaging modalities can only detect gross changes in the cochlea, and non-invasive in vivo cochlear
measurements are scarce. As a result, extensive efforts have been made to adapt optical coherence tomography (OCT)
techniques to analyze and study the cochlea. Herein, we detail the methods for measuring vibration using OCT. We
used spectral domain OCT with ~950 nm as the center wavelength and a bandwidth of ~80 nm. The custom
spectrometer used was based on a high speed line scan camera which is capable of line rates up to 28 kHz. The signal-to-
noise ratio of the system was ~90 dB. The data collection and processing software was written in LabVIEW and
MATLAB. We tested whether streaming directly from the camera, writing the data to multiple hard drives in the RAID-
0 configuration, and processing using the GPU shortened experiment times. We then analyzed the A-line phase noise
over several hundred milliseconds and growth curves from a piezoelectric element. We believe this is the first step
towards a diagnostic device which generates vibration information of cochlear structures.
Skin cancer is the most common form of human cancer. Its early diagnosis and timely treatment is of paramount importance for dermatology and surgical oncology. In this study, we evaluate the use of reflectance and fluorescence confocal microscopy for detecting skin cancers in an in-vivo trial with B16F10 melanoma and SCCVII squamous cell carcinoma in mice. For the experiments, the mice are anesthetized, then the tumors are infiltrated with aqueous solution of methylene blue and imaged. Reflectance images are acquired at 658 nm. Fluorescence is excited at 658 nm and registered in the range between 690 and 710 nm. After imaging, the mice are sacrificed. The tumors are excised and processed for hematoxylin and eosin histopathology, which is compared to the optical images. The results of the study indicate that in-vivo reflectance images provide valuable information on vascularization of the tumor, whereas the fluorescence images mimic the structural features seen in histopathology. Simultaneous dye-enhanced reflectance and fluorescence confocal microscopy shows promise for the detection, demarcation, and noninvasive monitoring of skin cancer development.
Here we report on our current efforts to simultaneously quantify both morphological and biochemical tissue information
by combining optical coherence tomography (OCT) and fluorescence lifetime imaging (FLIM). The Fourier domain
OCT module is built around a custom designed high-speed spectrometer (bandwidth of 102 nm, 3 dB rolloff of 1.2 mm,
lines rates of up to 59 kHz). A 40 nm bandwidth SLED centered at 830 nm provided an axial resolution of 7.6 mm for
OCT. The objective lens provided 10 um lateral resolution for OCT and 100 um for FLIM. Lateral OCT and FLIM beam
scanning was accomplished using a set of galvo mirrors. The FLIM module excites and collects the fluorescence decay
signal pixel by pixel coincident with OCT A-line collection. Each 2-D FLIM image has a corresponding coregistered
OCT volume. Fluorescence excitation for FLIM was provided by a solid-state pulse laser (355 nm, 1 ns FWHM, 50 kHz
rep rate). The fluorescence signal was detected with a MCP-PMT coupled to a 1.5 GHz digitizer (250 ps temporal
resolutions). In addition, simultaneous multispectral time-resolved fluorescence detection was achieved by separating the
fluorescence emission in three bands using a series of dichroic mirrors and bandpass filters, and launching each band into
three fibers of different lengths (providing a time delay of 50 ns among bands) focused onto the MCP-PMT. The
resulting OCT/FLIM system is capable of a maximum A-line rate of 59 kHz for OCT and a maximum pixel rate of at
least 30 kHz for FLIM. The multimodality OCT/FLIM imaging system was validated on biological tissue. Future efforts
include evaluating its potential for oral cancer diagnosis and intravascular imaging.
We demonstrate the feasibility of a time-resolved fluorescence spectroscopy (TRFS) technique for intraluminal investigation of arterial vessel composition under intravascular ultrasound (IVUS) guidance. A prototype 1.8-mm (5.4 Fr) catheter combining a side-viewing optical fiber (SVOF) and an IVUS catheter was constructed and tested with in vitro vessel phantoms. The prototype catheter can locate a fluorophore in the phantom vessel wall, steer the SVOF in place, perform blood flushing under flow conditions, and acquire high-quality TRFS data using 337-nm wavelength excitation. The catheter steering capability used for the coregistration of the IVUS image plane and the SVOF beam produce a guiding precision to an arterial phantom wall site location of 0.53±0.16 mm. This new intravascular multimodal catheter enables the potential for in vivo arterial plaque composition identification using TRFS.
A unique tissue phantom is reported here that mimics the optical and acoustical properties of biological tissue and
enables testing and validation of a dual-modality clinical diagnostic system combining time-resolved laser-induced
fluorescence spectroscopy (TR-LIFS) and ultrasound backscatter microscopy (UBM). The phantom consisted of contrast
agents including silicon dioxide particles with a range of diameters from 0.5 to 10 μm acting as optical and acoustical
scatterers, and FITC-conjugated dextran mimicking the endogenous fluorophore in tissue. The agents were encapsulated
in a polymer bead attached to the end of an optical fiber with a 200 μm diameter using a UV-induced polymerization
technique. A set of beads with fibers were then implanted into a gel-based matrix with controlled patterns including a
design with lateral distribution and a design with successively changing depth. The configuration presented here allowed
the validation of the hybrid fluorescence spectroscopic and ultrasonic system by detecting the lateral and depth
distribution of the contrast agents, as well as for coregistration of the ultrasonic image with spectroscopic data. In
addition, the depth of the beads in the gel matrix was changed to explore the effect of different concentration ratio of the
mixture on the fluorescence signal emitted.
Characterizing and quantifying noise sources in birefringence imaging with polarization-sensitive optical coherence tomography (PS-OCT) is necessary for the development of efficient noise reduction techniques for real-time clinical PS-OCT imaging. We propose three noise regimes based on the strength of specimen backscattering and dominated by different noise sources. We introduce a model that predicts noise effects in two regimes. The model includes source/detector intensity noise, and couples speckle effects with the longitudinal delays due to instrument and specimen birefringence to create realistic noise on simulated orthogonal interference fringe amplitudes and on their relative phases. Experimental examples of the three regimes are presented and in two of them, qualitative agreement between the model and experimental data is demonstrated.
Form-birefringent properties of the retinal nerve fiber layer (RNFL) have become increasingly important as investigators strive to provide an improved methodology for glaucoma diagnosis. Techniques such as scanning laser polarimetry (SLP) and polarization-sensitive optical coherence tomography (PS-OCT) are two approaches which directly assess RNFL neurotubules, the sub-cellular structures responsible for form-birefringence and axoplasmic transport in retinal ganglion cell axons. We present a novel algorithm for enhancing the sensitivity of PS-OCT. Enhanced polarization-sensitive OCT (EPS-OCT) is capable of detecting small transformations in polarization typically experienced by light propagating through the thin and weakly birefringent primate RNFL. We report birefringence and nerve fiber orientation measurements for the peripapillary region in healthy in vivo primate RNFL and discuss the implications of the enhanced-sensitivity approach on noninvasive quantification of form-birefringence in glaucoma diagnostics.
Polarization-Sensitive Optical Coherence Tomography (PS-OCT) has been used to measure birefringence of biological samples, namely the retinal nerve fiber layer (RNFL). The presence of blood vessels in biological samples complicates accurate measurement of tissue birefringence as a result of the Doppler shift in fringe frequency and the shadowing effect below blood vessels due to absorption and scattering of light photons by blood. We investigate phase retardation measurement with controlled capillary blood flow overlying a birefringent sample with enhanced polarization-sensitivity optical coherence tomography (EPS-OCT). The effect of blood flow on the calculation of phase retardation and tissue birefringence was studied in the polarization domain. Light propagating through an overlying moving turbid medium (blood) undergoes single or multiple forward scattering events and a Doppler shift in presence of flow. Light propagating through an overlying medium may introduce Doppler shifts of each polarization component and/or polarization shifts or retardation of light. While undergoing multiple forward scattering, each scattering event can modify the frequency or light phase delay. In successive scattering events, potential Doppler shifts and/or polarization shifts accumulate. Light propagating within the birefringent sample undergoes multiple forward scattering events leading to phase retardation between polarization components. This paper investigates phase retardation measurement underlying physiological blood flow rates (6, 12, 18, and 24μl/min) at a range of light incident angle (0-20 deg.) on the sample. With EPS-OCT, the effect of light scattering and differential Doppler shifts between the polarization modes on the measurement of phase retardation was within our speckle noise range.
Phase retardation per unit depth (PR/UD) is a physiologically significant parameter which correlates with the orderly arrangement of neurons and neurofibrils within the retinal nerve fiber layer (RNFL) and can vary in glaucoma. The objective of this study is to use Polarization Sensitive Optical Coherence Tomography (PSOCT), to detect both RNFL thickness and depth-resolved birefringence and produce thickness and PR/UD maps of the primate RNFL. RNFL
thickness is obtained from the PSOCT intensity image with boundary detection using imaging processing methods. Analysis of PR/UD begins with calculating the Stokes parameters from the horizontal magnitude, vertical magnitude and relative phase difference in the interference fringes of light back scattered from the retina. Computed Stokes parameters are used to determine the fast axis in the RNFL and local phase retardation. PR/UD is calculated by dividing local birefringence by the corresponding RNFL thickness. A three-dimensional map of PR/UD and RNFL thickness is constructed by combining registered B-scans. Three-dimensional maps of thickness and PR/UD from the primate RNFL show that PSOCT is can be used for detecting thickness and PR/UD of the peripapillary RNFL and a very effective modality to diagnose glaucoma.
Imaging the optical phase retardation per unit depth (OPR/UD) in the retinal nerve fiber layer (RNFL) may aid in glaucoma diagnosis. Polarization Sensitive Optical Coherence Tomography (PSOCT) was used to record in vivo high-resolution images of the RNFL in two cynomologous monkeys. The depth variation in the Stokes vector of reflected light was used to calculate the OPR/UD as a function of RNFL position. OPR/UD decreased from 35 degree(s)/100 micrometers near the optic nerve to 5 degree(s)/100 micrometers at a location 600 micrometers superior to the optic nerve. Variation of OPR/UD in the RNFL with retinal position demonstrates a change in birefringence for different densities of ganglion cell axons. PSOCT may be useful for noninvasive determination of RNFL thickness and fiber density.
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