We report the use of optical coherence tomography (OCT) to determine spatially localized optical attenuation coefficients of human axillary lymph nodes and their use to generate parametric images of lymphoid tissue. 3D-OCT images were obtained from excised lymph nodes and optical attenuation coefficients were extracted assuming a single scattering model of OCT. We present the measured attenuation coefficients for several tissue regions in benign and reactive lymph nodes, as identified by histopathology. We show parametric images of the measured attenuation coefficients as well as segmented images of tissue type based on thresholding of the attenuation coefficient values. Comparison to histology demonstrates the enhancement of contrast in parametric images relative to OCT images. This enhancement is a step towards the use of OCT for in situ assessment of lymph nodes.
Histologic assessment is the gold standard technique for the identification of metastatic involvement of lymph nodes in malignant disease, but can only be performed ex vivo and often results in the unnecessary excision of healthy lymph nodes, leading to complications such as lymphedema. Optical coherence tomography (OCT) is a high-resolution, near-IR imaging modality capable of visualizing microscopic features within tissue. OCT has the potential to provide in vivo assessment of tissue involvement by cancer. In this morphologic study, we show the capability of OCT to image nodal microarchitecture through an assessment of fresh, unstained ex vivo lymph node samples. Examples include both benign human axillary lymph nodes and nodes containing metastatic breast carcinoma. Through accurate correlation with the histologic gold standard, OCT is shown to enable differentiation of lymph node tissue from surrounding adipose tissue, reveal nodal structures such as germinal centers and intranodal vessels, and show both diffuse and well circumscribed patterns of metastatic node involvement. Cancer Res; 70(7); 2579-84. ©2010 AACR.
Abstract. We present a parametric optical coherence tomography ͑OCT͒ technique to improve contrast between malignant and healthy non-neoplastic tissue. The technique incorporates a fully automated method to extract tissue attenuation characteristics. Results are represented visually as a parametric en face image, where the parameter used for contrast is indicative of the relative optical attenuation coefficient of the tissue. We present the first parametric OCT images of human lymph nodes containing malignant cells, and demonstrate improved tissue contrast over en face OCT images.
We present a high-optical-quality imaging needle for optical coherence tomography (OCT) that achieves sensitivity and resolution comparable to conventional free-space OCT sample arms. The side-viewing needle design utilizes total internal reflection from an angle-polished fiber tip, encased in a glass microcapillary. Fusion of the capillary to the fiber provides a robust, optical-quality output window. The needle's focusing optics are based on an astigmatism-free design, which exploits the "focal shift" phenomenon for focused Gaussian beams to achieve equal working distances (WDs) for both axes. We present a fabricated needle with a WD ratio of 0.98 for imaging in an aqueous environment. Our needle achieves the highest sensitivity of currently reported OCT imaging needles (112 dB), and we demonstrate its performance by superficial imaging of human skin and 3D volumetric imaging within a biological sample.
Molecular imaging using optical techniques provides insight into disease at the cellular level. In this paper, we report on a novel dualmodality probe capable of performing molecular imaging by combining simultaneous three-dimensional optical coherence tomography (OCT) and two-dimensional fluorescence imaging in a hypodermic needle. The probe, referred to as a molecular imaging (MI) needle, may be inserted tens of millimeters into tissue. The MI needle utilizes double-clad fiber to carry both imaging modalities, and is interfaced to a 1310-nm OCT system and a fluorescence imaging subsystem using an asymmetrical double-clad fiber coupler customized to achieve high fluorescence collection efficiency. We present, to the best of our knowledge, the first dual-modality OCT and fluorescence needle probe with sufficient sensitivity to image fluorescently labeled antibodies. Such probes enable high-resolution molecular imaging deep within tissue.
Abstract. This work presents a novel tissue-mimicking phantom for use in a range of optical coherence tomography ͑OCT͒ experiments. Such phantoms are critical in the development and assessment of new OCT techniques, but no previously published phantoms have become universally accepted. We present the first description of a phantom based on a fibrin matrix, which improves key attributes of previously published methods. It provides a biocompatible, optically transparent scaffold in which to incorporate organic and/or inorganic optical scattering materials. Its fabrication time is markedly shorter than many common phantoms, and its lifetime is longer than other biocompatible phantoms. The potential of fibrin phantoms incorporating Intralipid ™ to introduce uniform optical scattering is demonstrated. The measured attenuation coefficient as a function of Intralipid concentration confirms the ability to control optical scattering. A bilayer phantom with distinct optical scattering in each layer is also presented.
Optical coherence tomography (OCT) is a medical imaging modality that opens up new opportunities for imaging in breast cancer. It provides two-and threedimensional micro-scale images of tissue structure from bulk tissue, in vivo or freshly excised without labeling or staining, is capable of video-rate acquisition speeds, and is compatible with compact imaging probes. In this paper, the authors briefly describe OCT technology and describe in detail its capabilities for imaging breast cancer. Potential applications identified in current research are discussed, particularly in the assessment of excised breast tumors. It is concluded that OCT shows promise for margin assessment and biopsy guidance but that much more research and validation is required to confirm its level of utility. Zusammenfassung: Die optische Kohärenztomographie (optical coherence tomography, OCT) ist ein medizinisches Bildgebungsverfahren, das neue Möglichkeiten für die Bildgebung bei Brustkrebs eröffnet. Es liefert zweiund dreidimensionale Bilder im Mikrometerbereich; erlaubt die Darstellung von Gewebestrukturen großer Gewebevolumen, in vivo oder frisch exzidiert, ohne Markierung oder Färbung; arbeitet fast mit Videoaufnahmegeschwindigkeit und ist mit kompakten Imaging-Sonden kompatibel. Im vorliegenden Übersichtsartikel wird die OCT-Technologie kurz vorgestellt und deren Potential zur Bildgebung von Brustkrebs dargestellt. Mögliche Anwendungen, die derzeit Gegenstand aktueller Forschung sind, werden identifiziert und diskutiert, insbesondere ihr Einsatz zur Beurteilung exzidierter Brusttumoren. Die Autoren kommen zu dem Schluss, dass die OCT sich vielversprechend zeigt für die Tumorrandbestimmung und Biopsie-Führung, aber noch weitere Forschungsarbeit für die Validierung erforderlich ist, um den Grad des Nutzens zu bestätigen.
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