1. Articles from Adeel Ahmad

    1-17 of 17
    1. Intravascular magnetomotive optical coherence tomography of targeted early-stage atherosclerotic changes in ex vivo hyperlipidemic rabbit aortas

      Intravascular magnetomotive optical coherence tomography of targeted early-stage atherosclerotic changes in ex vivo hyperlipidemic rabbit aortas

      Representative magnetomotive signal (green) using targeted and non-targeted magnetomotive microspheres in atherosclerotic diseased rabbit aortas. We report the development of an intravascular magnetomotive optical coherence tomography (IV-MM-OCT) system used with targeted protein microspheres to detect early-stage atherosclerotic fatty streaks/plaques. Magnetic microspheres (MSs) were injected in vivo in rabbits, and after 30 minutes of in vivo circulation, excised ex vivo rabbit aorta samples specimens were then imaged ex vivo with our prototype IV-MM-OCT system. The alternating magnetic field gradient was provided by a unique pair of external custom-built electromagnetic coils that modulated the targeted magnetic MSs. The results showed a ...

      Read Full Article
    2. Volumetric full-range magnetomotive optical coherence tomography

      Volumetric full-range magnetomotive optical coherence tomography

      Magnetomotive optical coherence tomography (MM-OCT) can be utilized to spatially localize the presence of magnetic particles within tissues or organs. These magnetic particle-containing regions are detected by using the capability of OCT to measure small-scale displacements induced by the activation of an external electromagnet coil typically driven by a harmonic excitation signal. The constraints imposed by the scanning schemes employed and tissue viscoelastic properties limit the speed at which conventional MM-OCT data can be acquired. Realizing that electromagnet coils can be designed to exert MM force on relatively large tissue volumes (comparable or larger than typical OCT imaging fields of ...

      Read Full Article
    3. Computed optical interferometric tomography for high-speed volumetric cellular imaging

      Computed optical interferometric tomography for high-speed volumetric cellular imaging

      hree-dimensional high-resolution imaging methods are important for cellular-level research. Optical coherence microscopy (OCM) is a low-coherence-based interferometry technology for cellular imaging with both high axial and lateral resolution. Using a high-numerical-aperture objective, OCM normally has a shallow depth of field and requires scanning the focus through the entire region of interest to perform volumetric imaging. With a higher-numerical-aperture objective, the image quality of OCM is affected by and more sensitive to aberrations. Interferometric synthetic aperture microscopy (ISAM) and computational adaptive optics (CAO) are computed imaging techniques that overcome the depth-of-field limitation and the effect of optical aberrations in optical coherence ...

      Read Full Article
    4. Stability in computed optical interferometric tomography (Part II): in vivo stability assessment

      Stability in computed optical interferometric tomography (Part II): in vivo stability assessment

      Stability is of utmost importance to a wide range of phase-sensitive processing techniques. In Doppler optical coherence tomography and optical coherence elastography, in addition to defocus and aberration correction techniques such as interferometric synthetic aperture microscopy and computational/digital adaptive optics, a precise understanding of the system and sample stability helps to guide the system design and choice of imaging parameters. This article focuses on methods to accurately and quantitatively measure the stability of an imaging configuration in vivo . These methods are capable of partially decoupling axial from transverse motion and are compared against the stability requirements for computed optical ...

      Read Full Article
    5. Magnetomotive optical coherence elastography using magnetic particles to induce mechanical waves

      Magnetomotive optical coherence elastography using magnetic particles to induce mechanical waves

      Magnetic particles are versatile imaging agents that have found wide spread applicability in diagnostic, therapeutic, and rheology applications. In this study, we demonstrate that mechanical waves generated by a localized inclusion of magnetic nanoparticles can be used for assessment of the tissue viscoelastic properties using magnetomotive optical coherence elastography. We show these capabilities in tissue mimicking elastic and viscoelastic phantoms and in biological tissues by measuring the shear wave speed under magnetomotive excitation. Furthermore, we demonstrate the extraction of the complex shear modulus by measuring the shear wave speed at different frequencies and fitting to a Kelvin-Voigt model.

      Read Full Article
    6. Magnetomotive Optical Coherence Tomography for the Assessment of Atherosclerotic Lesions Using αvβ 3 Integrin-Targeted Microspheres

      Magnetomotive Optical Coherence Tomography for the Assessment of Atherosclerotic Lesions Using αvβ 3 Integrin-Targeted Microspheres

      Purpose We investigated the early-stage fatty streaks/plaques detection using magnetomotive optical coherence tomography (MM-OCT) in conjunction with α v β 3 integrin-targeted magnetic microspheres (MSs). The targeting of functionalized MSs was investigated by perfusing ex vivo aortas from an atherosclerotic rabbit model in a custom-designed flow chamber at physiologically relevant pulsatile flow rates and pressures. Procedures Aortas were extracted and placed in a flow chamber. Magnetic MS contrast agents were perfused through the aortas and MM-OCT, fluorescence confocal, and bright field microscopy were performed on the ex vivo aorta specimens for localizing the MSs. Results The results showed a statistically significant ...

      Read Full Article
    7. Feature Of The Week 5/12/13: University of Illinois at Urbana-Champaign Reports on Real-Time In Vivo Computed Optical Interferometric Tomography

      Feature Of The Week 5/12/13: University of Illinois at Urbana-Champaign Reports on Real-Time In Vivo Computed Optical Interferometric Tomography

      Real-time, high-resolution tomography over an extended field-of-view in scattering tissues remains an elusive goal for biomedical imaging. The apparent trade-off between the depth-of-field and lateral resolution in optical imaging degrades the image resolution outside the confocal region in OCT. Although a number of approaches have been utilized to overcome these limitations, many of these techniques are plagued by either high computational complexity or complicated optical setups. ISAM is a computational technique that can yield spatially invariant transverse resolution by resampling the Fourier space of the data. However, a full 3D ISAM reconstruction requires extensive manipulation of volumetric datasets, imposing significant ...

      Read Full Article
    8. Real-time in vivo computed optical interferometric tomography

      Real-time in vivo computed optical interferometric tomography

      High-resolution real-time tomography of scattering tissues is important for many areas of medicine and biology 1 , 2 , 3 , 4 , 5 , 6 . However, the compromise between transverse resolution and depth-of-field, in addition to low sensitivity deep in tissue, continues to impede progress towards cellular-level volumetric tomography. Computed imaging has the potential to solve these long-standing limitations. Interferometric synthetic aperture microscopy 7 , 8 , 9 is a computed imaging technique enabling high-resolution volumetric tomography with spatially invariant resolution. However, its potential for clinical diagnostics remains largely untapped because full volume reconstructions required lengthy post-processing, and the phase-stability requirements have been difficult to satisfy ...

      Read Full Article
    9. Dual-coil magnetomotive optical coherence tomography for contrast enhancement in liquids

      Dual-coil magnetomotive optical coherence tomography for contrast enhancement in liquids

      Magnetomotive optical coherence tomography (MM-OCT) is a functional extension of OCT which utilizes magnetically responsive materials that are modulated by an external magnetic field for contrast enhancement and for elastography to assess the structural and viscoelastic properties of the surrounding tissues. Traditionally, magnetomotive contrast relies on the interaction between the displacement of magnetic particles induced by an external magnetic field and the micro-environmental restoring (elastic) force acting on the particles. When the restoring force from a sample containing magnetic particles is weak or non-existent, the MM-OCT signal-to-noise ratio (SNR) can degrade significantly. We have developed a novel solenoid configuration to ...

      Read Full Article
    10. Feature Of The Week 12/9/12: University of Illinois at Urbana Champaign Researchers Extend Astronomical Guide-Star Techniques to Computational OCT Imaging

      Feature Of The Week 12/9/12: University of Illinois at Urbana Champaign Researchers Extend Astronomical Guide-Star Techniques to Computational OCT Imaging

      Researchers at the University of Illinois at Urbana-Champaign have a long history of novel work in the field of OCT and related fields.  This includes the very promising area of computational adaptive optics and related methods that offer the promise of dramatically improved images in a wide variety of settings by performing post-acquisition processing of magnitude and phase data.  Below is a summary of some of their recent work.  Aberrations degrade resolution, contrast, and signal-to-noise ratio in optical microscopy. In optical coherence tomography (OCT), aberrations limit the resolution of diagnostic features, notably in retinal OCT. With optical coherence microscopy, which ...

      Read Full Article
    11. Guide-star-based computational adaptive optics for broadband interferometric tomography

      Guide-star-based computational adaptive optics for broadband interferometric tomography

      We present a method for the numerical correction of optical aberrations based on indirect sensing of the scattered wavefront from point-like scatterers (“guide stars”) within a three-dimensional broadband interferometric tomogram. This method enables the correction of high-order monochromatic and chromatic aberrations utilizing guide stars that are revealed after numerical compensation of defocus and low-order aberrations of the optical system. Guide-star-based aberration correction in a silicone phantom with sparse sub-resolution-sized scatterers demonstrates improvement of resolution and signal-to-noise ratio over a large isotome. Results in highly scattering muscle tissue showed improved resolution of fine structure over an extended volume. Guide-star-based computational adaptive ...

      Read Full Article
    12. Feature Of The Week 6/10/12: Computational Adaptive Optics: A New Digital Post-Processing Technique to Optimize Resolution in OCT and other Interferometric Optical Imaging Applications

      Feature Of The Week 6/10/12: Computational Adaptive Optics: A New Digital Post-Processing Technique to Optimize Resolution in OCT and other Interferometric Optical Imaging Applications

      OCT and other interferometric optical 2D and 3D imaging techniques have long been plagued by the fundamental optical limitations such as that which occurs between depth-of-field (Rayleigh range) and lateral resolution or limitations in image resolution due to optical aberrations (spatial and spectral) that occur within delivery or collection optics or within tissue themselves.  Over the past few years there have been a variety of new powerful post optical detection signal processing techniques that promise to shatter these traditional limitations and take OCT and other interferometric optical imaging techniques to a new level.  These techniques are all related on some ...

      Read Full Article
    13. Computational adaptive optics for broadband optical interferometric tomography of biological tissue

      Computational adaptive optics for broadband optical interferometric tomography of biological tissue

      Aberrations in optical microscopy reduce image resolution and contrast, and can limit imaging depth when focusing into biological samples. Static correction of aberrations may be achieved through appropriate lens design, but this approach does not offer the flexibility of simultaneously correcting aberrations for all imaging depths, nor the adaptability to correct for sample-specific aberrations for high-quality tomographic optical imaging. Incorporation of adaptive optics (AO) methods have demonstrated considerable improvement in optical image contrast and resolution in noninterferometric microscopy techniques, as well as in optical coherence tomography. Here we present a method to correct aberrations in a tomogram rather than the ...

      Read Full Article
    14. The impact of aberrations on object reconstruction with interferometric synthetic aperture microscopy

      The impact of aberrations on object reconstruction with interferometric synthetic aperture microscopy

      Interferometric synthetic aperture microscopy (ISAM) reconstructs the scattering potential of a sample with spatially invariant resolution, based on the incident beam profile, the beam scan pattern, the physical model of light sample interaction, and subsequent light collection by the system. In practice, aberrations may influence the beam profile, particularly at higher NA, when ISAM is expected to provide maximum benefit over optical coherence microscopy. Thus it is of interest to determine the effects of aberrations on ISAM reconstructions. In this paper we present the forward model incorporating the effects of aberrations, which forms the basis for aberration correction in ISAM ...

      Read Full Article
    15. Numerical analysis of gradient index lens based optical coherence tomography imaging probes

      Numerical analysis of gradient index lens based optical coherence tomography imaging probes

      We report the numerical analysis of gradient index (GRIN) lens-based optical coherence tomography imaging probes to derive optimal design parameters. Long and short working distance probes with a small focal spot are considered. In each model, the working distance and beam waist are characterized and compared for different values of length and refractive index of the probe components. We also explore the influence of the outer tubing and refractive index of the sample media. Numerical results show that the adjustment of the maximum beam diameter and focusing angle at the end of the GRIN lens surface is very important for ...

      Read Full Article
    16. Sonification of optical coherence tomography data and images

      Sonification of optical coherence tomography data and images

      Sonification is the process of representing data as non-speech audio signals. In this manuscript, we describe the auditory presentation of OCT data and images. OCT acquisition rates frequently exceed our ability to visually analyze image-based data, and multi-sensory input may therefore facilitate rapid interpretation. This conversion will be especially valuable in time-sensitive surgical or diagnostic procedures. In these scenarios, auditory feedback can complement visual data without requiring the surgeon to constantly monitor the screen, or provide additional feedback in non-imaging procedures such as guided needle biopsies which use only axial-scan data. In this paper we present techniques to translate OCT ...

      Read Full Article
    17. Cross-correlation-based image acquisition technique for manually-scanned optical coherence tomography

      Cross-correlation-based image acquisition technique for manually-scanned optical coherence tomography

      We present a novel image acquisition technique for Optical Coherence Tomography (OCT) that enables manual lateral scanning. The technique compensates for the variability in lateral scan velocity based on feedback obtained from correlation between consecutive A-scans. Results obtained from phantom samples and biological tissues demonstrate successful assembly of OCT images from manually-scanned datasets despite non-uniform scan velocity and abrupt stops encountered during data acquisition. This technique could enable the acquisition of images during manual OCT needle-guided biopsy or catheter-based imaging, and for assembly of large field-of-view images with hand-held probes during intraoperative in vivo OCT imaging.

      Read Full Article
    1-17 of 17
  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
  2. Topics in the News

    1. (17 articles) University of Illinois at Urbana-Champaign
    2. (17 articles) Adeel Ahmad
    3. (17 articles) Stephen A. Boppart
    4. (11 articles) Steven G. Adie
    5. (9 articles) P. Scott Carney
    6. (8 articles) Nathan D. Shemonski
    7. (3 articles) Eric J. Chaney
    8. (3 articles) Marina Marjanovic
    9. (2 articles) Cornell University
    10. (2 articles) Utkarsh Sharma
  3. Popular Articles

  4. Picture Gallery

    Cross-correlation-based image acquisition technique for manually-scanned optical coherence tomography Sonification of optical coherence tomography data and images Numerical analysis of gradient index lens based optical coherence tomography imaging probes The impact of aberrations on object reconstruction with interferometric synthetic aperture microscopy Computational adaptive optics for broadband optical interferometric tomography of biological tissue Feature Of The Week 6/10/12: Computational Adaptive Optics: A New Digital Post-Processing Technique to Optimize Resolution in OCT and other Interferometric Optical Imaging Applications Guide-star-based computational adaptive optics for broadband interferometric tomography Feature Of The Week 12/9/12: University of Illinois at Urbana Champaign Researchers Extend Astronomical Guide-Star Techniques to Computational OCT Imaging Feature Of The Week 5/12/13: University of Illinois at Urbana-Champaign Reports on Real-Time In Vivo Computed Optical Interferometric Tomography Magnetomotive Optical Coherence Tomography for the Assessment of Atherosclerotic Lesions Using αvβ 3 Integrin-Targeted Microspheres Medical treatment of inflammatory punctual stenosis monitored by anterior segment optical coherence tomography Development and Validation of a Deep Learning System for Diagnosing Glaucoma Using Optical Coherence Tomography