1. Articles from DSpace@MIT

    dspace.mit.edu

  2. 1-24 of 28 1 2 »
    1. Development and translation of label-free functional microscopy based on optical coherence tomography (Thesis)

      Development and translation of label-free functional microscopy based on optical coherence tomography (Thesis)

      Optical coherence tomography (OCT), an imaging modality based on low coherence interferometry, can be extended to obtain various endogenous functional contrasts. This thesis focuses on the development and translation of angiographic and polarization sensitive (PS) OCT techniques for clinical and preclinical applications. This goal includes four specific aims. The first aim is to develop a clinical imaging system to image the anatomy and microvasculature of human skin. The second aim is to develop a high performance post-processing algorithm for angiographic OCT. Towards this aim, we developed a processing algorithm based on complex differential variance (CDV) and confirmed its performance by ...

      Read Full Article
    2. Novel endoscopes for microscopic assessment of airway clearance using micro-optical coherence tomography (Thesis)

      Novel endoscopes for microscopic assessment of airway clearance using micro-optical coherence tomography (Thesis)

      The health of the human respiratory system depends critically on airway clearance via motile hair-like structures (cilia), which transport and eliminate unwanted particles trapped within mucus. Impairment of mucociliary clearance (MCC) can lead to life-threatening airway narrowing and lung infections, and is a major cause of morbidity and mortality in patients with cystic fibrosis, primary ciliary dyskinesia and chronic obstructive lung disease. However, no tool for microscopic in-vivo visualization of ciliary function is currently available, limiting studies of disease pathogenesis, refined diagnosis and phenotyping, and the development of novel therapeutics. In this thesis, a novel, 1-pm resolution, optical interferometric imaging ...

      Read Full Article
    3. Forward viewing OCT endomicroscopy (Thesis)

      Forward viewing OCT endomicroscopy (Thesis)

      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 ...

      Read Full Article
    4. Measurement of retinal vascular permeability in a rat model using spectroscopic optical coherence tomography

      Measurement of retinal vascular permeability in a rat model using spectroscopic optical coherence tomography

      Optical coherence tomography (OCT), a diagnostic tool which can perform non-contact, noninvasive, cross-sectional imaging of the retina and anterior eye in real time, has dramatically improved in its resolution and speed in the recent years. In addition to the advancement in hardware, different OCT methods for functional measurements, such as Doppler OCT for quantifying blood flow and generating angiography using OCT phase information, polarization sensitive OCT for measuring intrinsic mechanical / optical tissue property using light of different polarizations, and spectroscopic OCT for measuring blood oxygenation using multiple wavelengths, have been demonstrated and developed. In this thesis, a dual-wavelength spectroscopic OCT ...

      Read Full Article
    5. An optical smart needle : point-of-care technologies for integrated needle guidance using optical frequency domain ranging (Thesis)

      An optical smart needle : point-of-care technologies for integrated needle guidance using optical frequency domain ranging (Thesis)
      Obtaining accurate needle placement is of critical importance in many medical scenarios. In the setting of fine needle aspiration biopsy (FNAB), manual palpation is often the only cue for determining the optimal position of the needle. As a result, FNAB procedures frequently yield non-diagnostic tissue. When not guided by an imaging modality, breast and thyroid FNAB's only obtain diagnostic tissue in approximately 65% of cases. Although the addition of noninvasive imaging technology has been shown to increase FNAB yield, it is time-consuming, relatively expensive, and often requires additional personnel with specialized expertise. A need exists for low-cost, small, simple ...
      Read Full Article
    6. Applications of Fourier Domain Mode Locked lasers for optical coherence tomography imaging (Thesis)

      Applications of Fourier Domain Mode Locked lasers for optical coherence tomography imaging (Thesis)
      Optical coherence tomography (OCT) is a micrometer-resolution imaging technique that produces cross-sectional images of sample microstructure by measuring the amplitude and echo time delay of backscattered light. OCT imaging is performed using low-coherence interferometry, typically with a fiber optic Michelson interferometer. OCT imaging has recently been performed by measuring the spectrum of the interference signal in the Fourier domain. In "swept source OCT" implementations, the interference spectra are generated with a wavelength-swept laser and photodetector. Axial image lines are obtained via Fourier transformation of the spectra. Fourier domain techniques have extended OCT imaging speeds from several thousand to hundreds of ...
      Read Full Article
    7. Spectral/ Fourier domain Doppler Optical Coherence Tomography in the rodent retina (Thesis)

      Spectral/ Fourier domain Doppler Optical Coherence Tomography in the rodent retina (Thesis)
      Optical Coherence Tomography (OCT) is an emerging imaging technique based on low-coherence interferometry for noninvasive, high- resolution, cross-sectional imaging in a variety of biomedical fields. In ophthalmology, OCT has rapidly become a standard clinical diagnostic tool for retinal diseases, providing visualization of the retina with unprecedented detail. However, conventional time domain OCT systems are limited by low imaging speeds. Conventional time domain OCT systems use a mechanically scanned reference mirror to adjust the reference arm path length in time. Spectral / Fourier domain OCT systems use a spectrometer to detect the interference spectrum and do not require mechanical scanning of the ...
      Read Full Article
    8. Phase-sensitive light: coherence theory and applications to optical imaging (Thesis)

      Phase-sensitive light: coherence theory and applications to optical imaging (Thesis)
      Spontaneous parametric downconversion (SPDC) can produce pairs of entangled photons, i.e., a stream of biphotons. SPDC has been utilized in a number of optical imaging applications, such as optical coherence tomography, ghost imaging, holography and lithography, to obtain performance that cannot be realized with standard optical sources. However, a debate continues as to whether the improved imaging characteristics of such systems should be attributed to the entanglement property of the photon pairs. This thesis sets out to unify--and generalize--classical and quantum imaging within the framework of Gaussian-state light fields, which encompasses thermal light--the source used in conventional imagers--and biphoton-state ...
      Read Full Article
    9. High-speed Fourier domain Optical Coherence Tomography for structural and functional imaging of the retina (Thesis)

      High-speed Fourier domain Optical Coherence Tomography for structural and functional imaging of the retina (Thesis)
      Optical Coherence Tomography (OCT) is an emerging optical biomedical imaging technology that enables cross-sectional imaging of scattering tissue with high sensitivity and micron-scale resolution. In conventional OCT, the reference arm path length in a Michelson interferometer is scanned in time to generate a profile of backscattering versus depth from the sample arm. In conventional OCT, a broadband, low coherence light source is used to achieve high axial resolution. However, clinical and research applications of conventional OCT have been limited by low imaging speeds. Recently, new Fourier domain OCT detection methods have enabled speeds of ~20,000-40,000 axial scans per ...
      Read Full Article
    10. Advances in Optical Coherence Tomography and Microscopy for endoscopic applications and functional neuroimaging (Thesis)

      Advances in Optical Coherence Tomography and Microscopy for endoscopic applications and functional neuroimaging (Thesis)
      Optical Coherence Tomography (OCT) is a developing medical imaging technology that generates micron resolution cross-sectional images of subsurface internal tissue structure in situ and in real time, without the need to remove and process specimens. Previous studies have suggested that OCT holds great potential for use in laparoscopic and endoscopic applications to detect early stage neoplastic pathologies. A minimally invasive imaging modality capable of identifying pre-malignant tissues in vivo could be used to guide conventional excisional biopsy and histology, thereby reducing sampling error and enabling earlier detection and treatment. One limitation of prior endoscopic OCT imaging methods is the inability ...
      Read Full Article
    11. New technologies for optical coherence microscopy (Thesis)

      New technologies for optical coherence microscopy (Thesis)
      According to the American Cancer Society, gastrointestinal (GI) cancers are among the most common forms of malignancies suffered today, affecting -200,000 people and causing -80,000 deaths in the United States every year. The prognosis depends heavily on the detection of early-stage lesions. The process of endoscopic surveillance, excisional biopsy, and histologic examination is the current gold standard for screening and diagnosis of many GI cancers. This process, however, is invasive, time-consuming, and can suffer from unacceptable false negative rates. Optical imaging technology that provides real-time, high-resolution imaging of human tissue in vivo with resolution at or near that ...
      Read Full Article
    12. Spectral-domain optical coherence phase microscopy for quantitative biological studies (Thesis)

      Spectral-domain optical coherence phase microscopy for quantitative biological studies (Thesis)
      Conventional phase-contrast and differential interference contrast microscopy produce high contrast images of transparent specimens such as cells. However, they do not provide quantitative information or do not have enough sensitivity to detect nanometerlevel structural alterations. We have developed spectral-domain optical coherence phase microscopy (SD-OCPM) for highly sensitive quantitative phase imaging in 3D. This technique employs common-path spectral-domain optical coherence reflectometry to produce depth-resolved reflectance and quantitative phase images with high phase stability. The phase sensitivity of SD-OCPM was measured as nanometer-level for cellular specimens, demonstrating the capability for detecting small structural variation within the specimens. We applied SD-OCPM to the ...
      Read Full Article
    13. Design and fabrication of an optical pressure micro sensor for skin mechanics studies (Thesis)

      Design and fabrication of an optical pressure micro sensor for skin mechanics studies (Thesis)
      The mechanics of skin is as central to touch as optics is to vision and acoustics is to hearing. With the advent of novel imaging technologies such as the Optical Coherence Tomography (OCT), we are now able to view structures within the skin to a resolution of a few microns in vivo and non-invasively. To fully understand the role of biomechanics of the skin in interpreting touch, we need to develop a quantitative understanding of how spatio temporal loads imposed on the surface of the skin are transmitted to mechanoreceptor locations within the skin. The following thesis presents a description ...
      Read Full Article
    14. Optical frequency domain imaging of human retina and choroid (Thesis)

      Optical frequency domain imaging of human retina and choroid (Thesis)
      Optical coherence tomography (OCT) has emerged as a practical noninvasive technology for imaging the microstructure of the human eye in vivo. Using optical interferometry to spatially-resolve backreflections from within tissue, this high-resolution technique provides cross-sectional images of the anterior and posterior eye segments that had previously only been possible with histology. Current commercially-available OCT systems suffer limitations in speed and sensitivity, preventing them from effective screening of the retina and having a larger impact on the clinical environment. While other technological advances have addressed this problem, they are inadequate for imaging the choroid, which can be useful for evaluating choroidal ...
      Read Full Article
    15. Tactile sensing of shape: biomechanics of contact investigated using imaging and modeling (Thesis)

      Tactile sensing of shape: biomechanics of contact investigated using imaging and modeling (Thesis)
      The overall goal of this research effort is to improve the understanding of the biomechanics of skin as it pertains to human tactile sense. During touch, mechanoreceptors beneath the skin surface are mechanically loaded due to physical contact of the skin with an object and respond with a series of neural impulses. This neural population response is decoded by the central nervous system to result in tactile perception of properties such as the shape, surface texture and softness of the object. The particular approach taken in this research is to develop a realistic model of the human fingertip based on ...
      Read Full Article
    16. Estimation of nonlinear mechanical properties of atherosclerotic plaques (Thesis)

      Estimation of nonlinear mechanical properties of atherosclerotic plaques (Thesis)
      A numerical method has been developed to estimate the mechanical properties of atherosclerotic plaques by combining genetic algorithm with finite element methods. Plaque images derived from optical coherence tomography were employed to construct finite element models which were subsequently used in conjunction with a genetic algorithm to determine the parameters in a nonlinear constitutive model. A new multi-frame scheme is introduced to better perform the estimation on a nonlinear mechanical model and reduce the effects of noise. Results show while it is feasible to estimate the nonlinear mechanical properties of plaque, the accuracy can depend on various factors, especially the ...
      Read Full Article
    17. Enhanced visualization of retinal pathologies with ultrahigh resolution optical coherence tomography (Thesis)

      Enhanced visualization of retinal pathologies with ultrahigh resolution optical coherence tomography (Thesis)
      Current clinical practice calls for the development of techniques to diagnose diseases in its early stages, when treatment is most effective and significant irreversible damage can either be prevented or delayed. Optical coherence tomography (OCT) is an emerging medical diagnostic technology being investigated for applications in a number of medical fields including ophthalmology, cardiology, and gastroenterology. OCT is analogous to ultrasound except that it uses light waves rather than sound waves. OCT can achieve a much higher resolution than ultrasound in measuring the underlying tissue microstructures. Another advantage of OCT is that it can achieve imaging in a non-contact and ...
      Read Full Article
    18. Ultrahigh resolution optical coherence tomography for the detection of early stage neoplastic pathologies (Thesis)

      Ultrahigh resolution optical coherence tomography for the detection of early stage neoplastic pathologies (Thesis)
      Identification of changes associated with early stage disease remains a critical objective of clinical detection and treatment. Effective screening and detection is important for improving outcome because advanced disease, such as metastatic cancer, can be difficult to impossible to cure. Many existing diagnostic modalities, including x-ray imaging, magnetic resonance imaging, ultrasound, and endoscopy do not have sufficient resolution to detect changes in architectural morphology associated with early neoplasia and other pathologies. Diagnostic modalities capable of identifying pre-malignant tissue at an early stage could therefore significantly improve treatment outcome. Optical coherence tomography (OCT) is an emerging biomedical imaging technique that can ...
      Read Full Article
    19. Optical measurement of neural action potentials using low coherence heterodyne interferometry (Thesis)

      Optical measurement of neural action potentials using low coherence heterodyne interferometry (Thesis)
      We present a novel non-invasive optical method for detection of neural action potentials using low coherence interferometry. The dual beam heterodyne interferometer (DBHI) is a modified Michelson with a low coherence source and an optical referencing method capable of detecting sub-nanometer optical path changes. In this interferometer, acousto-optical modulators were used to produce an interfering heterodyne signal between the sample and a nearby surface. To cancel the noise, a differential phase measurement was made between this heterodyne signal and a stable reference heterodyne. DBHI has a stability of 30 picometers over 100ms. We have used this interferometer to measure the ...
      Read Full Article
    20. Tissue spectroscopic characterization based on fluorescence, second harmonic generation, and reflected light (Thesis)

      Tissue spectroscopic characterization based on fluorescence, second harmonic generation, and reflected light (Thesis)
      The diagnosis of many diseases often requires a histological analysis of tissues. Histology analysis compares the microscopic structure of a tissue specimen with an image database containing known physiological and pathological tissue structures. Three new microscopy technologies are developed to complement histology based on novel contrast mechanisms to better visualize and understand tissue structure and function: two-photon spectral resolved imaging, tri-modal imaging, and interferometric second harmonic imaging. First, two-photon spectral resolved microscopy utilizes the 3D localization ability of two-photon excitation to extract spectroscopic information from a femtoliter volume in tissue. The method is capable of the identification of biochemical species ...
      Read Full Article
    21. Elastography of coronary vessels using optical coherence tomography (Thesis)

      Elastography of coronary vessels using optical coherence tomography (Thesis)
      Atherosclerosis is an inflammatory disease characterized by an accumulation of lipid and fibrous tissue in the arterial wall. Postmortem studies have characterized rupture-prone atherosclerotic plaques by the presence of a large lipid=rich core covered by a thin fibrous cap. Studies employing finite element analysis (FEA) based on ex vivo plaque geometry have found that most plaques rupture at sites of high circumferential stress, thus diagnosis of plaque vulnerability may be enhanced by probing the mechanical behavior of individual plaques. Elastrography is a method of strain imaging in which an image sequence of the artery undergoing deformation is acquired, pixel ...
      Read Full Article
    22. Minimally invasive diagnostic imaging using high resolution Optical Coherence Tomography (Thesis)

      Minimally invasive diagnostic imaging using high resolution Optical Coherence Tomography (Thesis)
      Advances in medical imaging have given researchers unprecedented capabilities to visualize, characterize and understand biological systems. Optical Coherence Tomography (OCT) is a high speed, high resolution imaging technique that utilizes low coherence interferometry to perform cross-sectional tomographic imaging of tissue in real time and in vivo. The design, development, and implementation of ultrahigh resolution OCT systems in both laboratory and clinical experiments has been pursued in this work. Biomedical imaging studies in the areas of arthroscopy, cardiology, and endoscopy have been investigated with ultrahigh resolution capability achieved through the use of broadband femtosecond oscillators such as Ti:Sapphire and Cr ...
      Read Full Article
    23. Digital signal processing techniques for optical coherence tomography: OCT and OCT image enhancement (Thesis)

      Digital signal processing techniques for optical coherence tomography: OCT and OCT image enhancement (Thesis)
      Digital signal processing (DSP) techniques were developed to improve the flexibility, functionality, and image quality of ultrahigh resolution optical coherence tomography (OCT) systems. To reduce the dependence of OCT research systems on fixed analog electronics and to improve overall system flexibility, a digital demodulation scheme implemented entirely in software was developed. This improvement allowed rapid reconfiguration of the OCT imaging speed and source center wavelength without having to construct new analog filters and demodulators. This demodulation scheme produced a highly accurate envelope and was immune to local variations in carrier frequency. To provide an alternative contrast modality to conventional intensity-based ...
      Read Full Article
    24. High resolution imaging of neoplasma using optical coherence tomography (Thesis)

      High resolution imaging of neoplasma using optical coherence tomography (Thesis)
      Diagnostic imaging technologies for the detection of cancer include CT, MRI, ultrasonography, and endoscopy. However, many early neoplastic changes remain beyond their detection limits. A modality capable of imaging at or near the cellular level could detect disease at earlier stages than currently possible and thus improve patient prognosis. Optical coherence tomography (OCT) can achieve resolutions in the cellular and subcellular range (1-15 um) and could improve the diagnostic range of clinical imaging procedures.
      Read Full Article
    1-24 of 28 1 2 »
  1. Categories

    1. Applications:

      Art, Cardiology, Dentistry, Dermatology, Developmental Biology, Gastroenterology, Gynecology, Microscopy, NDE/NDT, Neurology, Oncology, Ophthalmology, Other Non-Medical, Otolaryngology, Pulmonology, Urology
    2. Business News:

      Acquisition, Clinical Trials, Funding, Other Business News, Partnership, Patents
    3. Technology:

      Broadband Sources, Probes, Tunable Sources
    4. Miscellaneous:

      Jobs & Studentships, Student Theses, Textbooks