1. Articles from Brendan F. Kennedy

    1-24 of 59 1 2 3 »
    1. Multi-class classification of breast tissue using optical coherence tomography and attenuation imaging combined via deep learning

      Multi-class classification of breast tissue using optical coherence tomography and attenuation imaging combined via deep learning

      We demonstrate a convolutional neural network (CNN) for multi-class breast tissue classification as adipose tissue, benign dense tissue, or malignant tissue, using multi-channel optical coherence tomography (OCT) and attenuation images, and a novel Matthews correlation coefficient (MCC)-based loss function that correlates more strongly with performance metrics than the commonly used cross-entropy loss. We hypothesized that using multi-channel images would increase tumor detection performance compared to using OCT alone. 5,804 images from 29 patients were used to fine-tune a pre-trained ResNet-18 network. Adding attenuation images to OCT images yields statistically significant improvements in several performance metrics, including benign dense ...

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    2. Optical Coherence Elastography (Textbook)

      Optical Coherence Elastography (Textbook)

      Optical Coherence Elastography: Imaging Tissue Mechanics on the Micro-Scale provides a unique and practical overview of this important new fi eld, which has seen tremendous growth in the last decade. Using optical coherence tomography (OCT) to measure sample deformation, optical coherence elastography (OCE) provides visualization of the three-dimensional, micro-scale mechanical properties of tissues and biomaterials and has shown distinct promise for application across clinical medicine, biology, and tissue engineering. This timely book provides: • Detailed coverage of the key elements required for the successful implementation of OCE techniques, particularly OCT imaging, mechanical deformation, and image processing • Synthesis of theory, methodology, and ...

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    3. Coherence function-encoded optical palpation

      Coherence function-encoded optical palpation

      Optical palpation maps stress at the surface of biological tissue into 2D images. It relies on measuring surface deformation of a compliant layer, which to date has been performed with optical coherence tomography (OCT). OCT-based optical palpation holds promise for improved clinical diagnostics; however, the complexity and cost hinder broad adoption. In this Letter, we introduce coherence function-encoded optical palpation (CFE-OP) using a novel optical profilometry technique that exploits the envelope of the coherence function rather than its peak position, which is typically used to retrieve depth information. CFE-OP utilizes a Fabry–Perot laser diode (bandwidth, 2.2 nm) and ...

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    4. Speckle-dependent accuracy in phase-sensitive optical coherence tomography

      Speckle-dependent accuracy in phase-sensitive optical coherence tomography

      Phase-sensitive optical coherence tomography (OCT) is used to measure motion in a range of techniques, such as Doppler OCT and optical coherence elastography (OCE). In phase-sensitive OCT, motion is typically estimated using a model of the OCT signal derived from a single reflector. However, this approach is not representative of turbid samples, such as tissue, which exhibit speckle. In this study, for the first time, we demonstrate, through theory and experiment that speckle significantly lowers the accuracy of phase-sensitive OCT in a manner not accounted for by the OCT signal-to-noise ratio (SNR). We describe how the inaccuracy in speckle reduces ...

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    5. Optical palpation for tumor margin assessment in breast-conserving surgery

      Optical palpation for tumor margin assessment in breast-conserving surgery

      Intraoperative margin assessment is needed to reduce the re-excision rate of breast-conserving surgery. One possibility is optical palpation, a tactile imaging technique that maps stress (force applied across the tissue surface) as an indicator of tissue stiffness. Images (optical palpograms) are generated by compressing a transparent silicone layer on the tissue and measuring the layer deformation using optical coherence tomography (OCT). This paper reports, for the first time, the diagnostic accuracy of optical palpation in identifying tumor within 1 mm of the excised specimen boundary using an automated classifier. Optical palpograms from 154 regions of interest (ROIs) from 71 excised ...

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    6. Analysis of sensitivity in quantitative micro-elastography

      Analysis of sensitivity in quantitative micro-elastography

      Quantitative micro-elastography (QME), a variant of compression optical coherence elastography (OCE), is a technique to image tissue elasticity on the microscale. QME has been proposed for a range of applications, most notably tumor margin assessment in breast-conserving surgery. However, QME sensitivity, a key imaging metric, has yet to be systematically analyzed. Consequently, it is difficult to optimize imaging performance and to assess the potential of QME in new application areas. To address this, we present a framework for analyzing sensitivity that incorporates the three main steps in QME image formation: mechanical deformation, its detection using optical coherence tomography (OCT), and ...

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    7. Camera-based optical palpation

      Camera-based optical palpation

      Optical elastography is undergoing extensive development as an imaging tool to map mechanical contrast in tissue. Here, we present a new platform for optical elastography by generating sub-millimetre-scale mechanical contrast from a simple digital camera. This cost-effective, compact and easy-to-implement approach opens the possibility to greatly expand applications of optical elastography both within and beyond the field of medical imaging. Camera-based optical palpation (CBOP) utilises a digital camera to acquire photographs that quantify the light intensity transmitted through a silicone layer comprising a dense distribution of micro-pores (diameter, 30–100 µm). As the transmission of light through the micro-pores increases ...

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    8. Strain and elasticity imaging in compression optical coherence elastography: the two‐decade perspective and recent advances

      Strain and elasticity imaging in compression optical coherence elastography: the two‐decade perspective and recent advances

      Quantitative mapping of deformation and elasticity in optical coherence tomography has attracted much attention of researchers during the last two decades. However, despite intense effort it took ~15 years to demonstrate optical coherence elastography (OCE) as a practically useful technique. Similarly to medical ultrasound, where elastography was first realized using the quasi‐static compression principle and later shear‐wave‐based systems were developed, in OCE these two approaches also developed in parallel. However, although the compression OCE (C‐OCE) was proposed historically earlier in the seminal paper by J.Schmitt in 1998, breakthroughs in quantitative mapping of genuine local strains ...

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    9. Feature Of The Week 04.26.2020: Diagnostic Accuracy of Quantitative Micro-Elastography for Margin Assessment in Breast-Conserving Surgery

      Feature Of The Week 04.26.2020: Diagnostic Accuracy of Quantitative Micro-Elastography for Margin Assessment in Breast-Conserving Surgery

      Inadequate margins in breast-conserving surgery (BCS) are associated with an increased likelihood of local recurrence of breast cancer. Currently, approximately 20% of BCS patients require repeat surgery due to inadequate margins at the initial operation. Implementation of an accurate, intraoperative margin assessment tool may reduce this re-excision rate. This study determined, for the first time, the diagnostic accuracy of quantitative micro-elastography (QME), an optical coherence tomography (OCT)–based elastography technique that produces images of tissue microscale elasticity, for detecting tumor within 1 mm of the margins of BCS specimens. Simultaneous OCT and QME were performed on the margins of intact ...

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    10. Diagnostic Accuracy of Quantitative Micro-Elastography for Margin Assessment in Breast-Conserving Surgery

      Diagnostic Accuracy of Quantitative Micro-Elastography for Margin Assessment in Breast-Conserving Surgery

      Inadequate margins in breast-conserving surgery (BCS) are associated with an increased likelihood of local recurrence of breast cancer. Currently, approximately 20% of BCS patients require repeat surgery due to inadequate margins at the initial operation. Implementation of an accurate, intraoperative margin assessment tool may reduce this re-excision rate. This study determined, for the first time, the diagnostic accuracy of quantitative micro-elastography (QME), an optical coherence tomography (OCT)–based elastography technique that produces images of tissue microscale elasticity, for detecting tumor within 1 mm of the margins of BCS specimens. Simultaneous OCT and QME were performed on the margins of intact ...

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    11. Three‐dimensional mapping of the attenuation coefficient in optical coherence tomography to enhance breast tissue micro‐architecture contrast

      Three‐dimensional mapping of the attenuation coefficient in optical coherence tomography to enhance breast tissue micro‐architecture contrast

      Effective intraoperative tumor margin assessment is needed to reduce re‐excision rates in breast‐conserving surgery (BCS). Mapping the attenuation coefficient in optical coherence tomography (OCT) throughout a sample to create an image (attenuation imaging) is one promising approach. For the first time, three‐dimensional OCT attenuation imaging of human breast tissue micro‐architecture using a wide‐field (up to ~45 × 45 × 3.5 mm) imaging system is demonstrated. Representative results from three mastectomy and one BCS specimen (from 31 specimens) are presented with co‐registered postoperative histology. Attenuation imaging is shown to provide substantially improved contrast over OCT, delineating ...

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    12. Handheld volumetric manual compression‐based quantitative micro‐elastography

      Handheld volumetric manual compression‐based quantitative micro‐elastography

      Compression optical coherence elastography typically requires a mechanical actuator to impart a controlled uniform strain to the sample. However, for handheld scanning, this adds complexity to the design of the probe and the actuator stroke limits the amount of strain that can be applied. In this work, we present a new volumetric imaging approach that utilises bidirectional manual compression via the natural motion of the user's hand to induce strain to the sample, realising compact, actuator‐free, handheld compression optical coherence elastography. In this way, we are able to demonstrate rapid acquisition of three‐dimensional quantitative micro‐elastography (QME ...

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    13. Handheld probe for quantitative micro-elastography

      Handheld probe for quantitative micro-elastography

      Optical coherence elastography (OCE) has been proposed for a range of clinical applications. However, the majority of these studies have been performed using bulky, lab-based imaging systems. A compact, handheld imaging probe would accelerate clinical translation, however, to date, this had been inhibited by the slow scan rates of compact devices and the motion artifact induced by the user’s hand. In this paper, we present a proof-of-concept, handheld quantitative micro-elastography (QME) probe capable of scanning a 6 × 6 × 1 mm volume of tissue in 3.4 seconds. This handheld probe is enabled by a novel QME acquisition protocol that ...

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    14. Finger-mounted quantitative micro-elastography

      Finger-mounted quantitative micro-elastography

      We present a finger-mounted quantitative micro-elastography (QME) probe, capable of measuring the elasticity of biological tissue in a format that avails of the dexterity of the human finger. Finger-mounted QME represents the first demonstration of a wearable elastography probe. The approach realizes optical coherence tomography-based elastography by focusing the optical beam into the sample via a single-mode fiber that is fused to a length of graded-index fiber. The fiber is rigidly affixed to a 3D-printed thimble that is mounted on the finger. Analogous to manual palpation, the probe compresses the tissue through the force exerted by the finger. The resulting ...

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    15. Analysis of spatial resolution in phase-sensitive compression optical coherence elastography

      Analysis of spatial resolution in phase-sensitive compression optical coherence elastography

      Optical coherence elastography (OCE) is emerging as a method to image the mechanical properties of tissue on the microscale. However, the spatial resolution, a main advantage of OCE, has not been investigated and is not trivial to evaluate. To address this, we present a framework to analyze resolution in phase-sensitive compression OCE that incorporates the three main determinants of resolution: mechanical deformation of the sample, detection of this deformation using optical coherence tomography (OCT), and signal processing to estimate local axial strain. We demonstrate for the first time, through close correspondence between experiment and simulation of structured phantoms, that resolution ...

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    16. Handheld optical palpation of turbid tissue with motion-artifact correction

      Handheld optical palpation of turbid tissue with motion-artifact correction

      Handheld imaging probes are needed to extend the clinical translation of optical elastography to in vivo applications, yet such probes have received little attention. In this paper, we present the first demonstration of optical palpation using a handheld probe. Optical palpation is a variant of optical elastography that uses three-dimensional optical coherence tomography (3D-OCT) to provide maps of stress at the tissue surface under static compression. Using this technique, stiff features present beneath the surface of turbid tissues are identified, providing mechanical contrast complementary to the optical contrast provided by OCT. However, during handheld operation, relative motion between the probe ...

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    17. Clinical feasibility of optical coherence micro-elastography for imaging tumor margins in breast-conserving surgery

      Clinical feasibility of optical coherence micro-elastography for imaging tumor margins in breast-conserving surgery

      It has been demonstrated that optical coherence micro-elastography (OCME) provides additional contrast of tumor compared to optical coherence tomography (OCT) alone. Previous studies, however, have predominantly been performed on mastectomy specimens. Such specimens typically differ substantially in composition and geometry from the more clinically relevant wide-local excision (WLE) specimens excised during breast-conserving surgery. As a result, it remains unclear if the mechanical contrast observed is maintained in WLE specimens. In this manuscript, we begin to address this issue by performing a feasibility study of OCME on 17 freshly excised, intact WLE specimens. In addition, we present two developments required to ...

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    18. Optical palpation for the visualization of tumor in human breast tissue

      Optical palpation for the visualization of tumor in human breast tissue

      Accurate and effective removal of tumor in one operation is an important goal of breast‐conserving surgery. However, it is not always achieved. Surgeons often utilize manual palpation to assess the surgical margin and/or the breast cavity. Manual palpation, however, is subjective and has relatively low‐resolution. Here, we investigate a tactile imaging technique, optical palpation, for the visualization of tumor. Optical palpation generates maps of the stress at the surface of tissue under static preload compression. Stress is evaluated by measuring the deformation of a contacting thin compliant layer with known mechanical properties using optical coherence tomography. In ...

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    19. Wide-field quantitative micro-elastography of human breast tissue

      Wide-field quantitative micro-elastography of human breast tissue

      Currently, 20-30% of patients undergoing breast-conserving surgery require a second surgery due to insufficient surgical margins in the initial procedure. We have developed a wide-field quantitative micro-elastography system for the assessment of tumor margins. In this technique, we map tissue elasticity over a field-of-view of ~46 × 46 mm. We performed wide-field quantitative micro-elastography on thirteen specimens of freshly excised tissue acquired from patients undergoing a mastectomy. We present wide-field optical coherence tomography (OCT) images, qualitative (strain) micro-elastograms and quantitative (elasticity) micro-elastograms, acquired in 10 minutes. We demonstrate that wide-field quantitative micro-elastography can extend the range of tumors visible using OCT-based ...

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    20. Ultrahigh-Resolution Optical Coherence Elastography Images Cellular-Scale Stiffness of Mouse Aorta

      Ultrahigh-Resolution Optical Coherence Elastography Images Cellular-Scale Stiffness of Mouse Aorta

      Cellular-scale imaging of the mechanical properties of tissue has helped to reveal the origins of disease; however, cellular-scale resolution is not readily achievable in intact tissue volumes. Here, we demonstrate volumetric imaging of Young’s modulus using ultrahigh-resolution optical coherence elastography, and apply it to characterizing the stiffness of mouse aortas. We achieve isotropic resolution of better than 15 μ m over a 1-mm lateral field of view through the entire depth of an intact aortic wall. We employ a method of quasi-static compression elastography that measures volumetric axial strain and uses a compliant, transparent layer to measure surface axial stress ...

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    21. Microscale imaging of breast tumor margins using optical coherence elastography

      Microscale imaging of breast tumor margins using optical coherence elastography

      A variant of optical coherence elastography offers a promising method of distinguishing between tumor and breast tissue in lumpectomy specimens in an intraoperative time frame. 1 May 2017, SPIE Newsroom. DOI: 10.1117/2.1201702.006873 Breast-conserving surgery is the most common surgical procedure used in the treatment of early-stage breast cancer. 1 The aim of this surgery is to remove all malignant tissue such that the surgical margin is free of cancer, while preserving the breast and ensuring a good cosmetic outcome. Currently, accurate microscopic margin assessment is only available postoperatively, via histopathological examination, days after the surgery. Of ...

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    22. The emergence of optical elastography in biomedicine

      The emergence of optical elastography in biomedicine

      Optical elastography, the use of optics to characterize and map the mechanical properties of biological tissue, involves measuring the deformation of tissue in response to a load. Such measurements may be used to form an image of a mechanical property, often elastic modulus, with the resulting mechanical contrast complementary to the more familiar optical contrast. Optical elastography is experiencing new impetus in response to developments in the closely related fields of cell mechanics and medical imaging, aided by advances in photonics technology, and through probing the microscale between that of cells and whole tissues. Two techniques — optical coherence elastography and ...

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    23. Depth-encoded optical coherence elastography for simultaneous volumetric imaging of two tissue faces

      Depth-encoded optical coherence elastography for simultaneous volumetric imaging of two tissue faces

      Depth-encoded optical coherence elastography (OCE) enables simultaneous acquisition of two three-dimensional (3D) elastograms from opposite sides of a sample. By the choice of suitable path-length differences in each of two interferometers, the detected carrier frequencies are separated, allowing depth-ranging from each interferometer to be performed simultaneously using a single spectrometer. We demonstrate depth-encoded OCE on a silicone phantom and a freshly excised sample of mouse liver. This technique minimizes the required spectral detection hardware and halves the total scan time. Depth-encoded OCE may expedite clinical translation in time-sensitive applications requiring rapid 3D imaging of multiple tissue surfaces, such as tumor ...

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    24. Investigation of optical coherence micro-elastography as a method to visualize micro-architecture in human axillary lymph nodes

      Investigation of optical coherence micro-elastography as a method to visualize micro-architecture in human axillary lymph nodes

      Background Evaluation of lymph node involvement is an important factor in detecting metastasis and deciding whether to perform axillary lymph node dissection (ALND) in breast cancer surgery. As ALND is associated with potentially severe long term morbidity, the accuracy of lymph node assessment is imperative in avoiding unnecessary ALND. The mechanical properties of malignant lymph nodes are often distinct from those of normal nodes. A method to image the micro-scale mechanical properties of lymph nodes could, thus, provide diagnostic information to aid in the assessment of lymph node involvement in metastatic cancer. In this study, we scan axillary lymph nodes ...

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    1-24 of 59 1 2 3 »
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