Eva Lankenau

Optical coherence tomography of the human skin

BACKGROUND Optical coherence tomography (OCT) is a new diagnostic method for tissue characterization. OBJECTIVE We investigated normal and pathologic structures in human skin in several locations to evaluate the potential application of this technique to dermatology. METHODS Based on the principle of low-coherence interferometry, cross-sectional images of the human skin can be obtained in vivo with a high spatial resolution of about 15 microns. Within a penetration depth of 0.5 to 1.5 mm, structures of the stratum corneum, the living epidermis, and the papillary dermis can be distinguished. RESULTS Different layers could be detected that were differentiated by induction of experimental blisters and by comparison with corresponding histologic sections. Furthermore, OCT images of several skin diseases and tumors were obtained. CONCLUSION OCT is a promising new imaging method for visualization of morphologic changes of superficial layers of the human skin. It may be useful for noninvasive diagnosis of bullous skin diseases, skin tumors, and in vivo investigation of pharmacologic effects.

Optimizing Descemet Membrane Endothelial Keratoplasty Using Intraoperative Optical Coherence Tomography

IMPORTANCE Descemet membrane endothelial keratoplasty (DMEK) is a challenging procedure for the surgeon, particularly because of deficient visibility of the delicate tissue due to the natural en face view through the operating microscope. A cross-sectional view would greatly enhance intraoperative overview and enable the surgeon to better control the procedure. OBJECTIVE To retrospectively analyze the use of intraoperative optical coherence tomography (iOCT) for improving the safety of DMEK. DESIGN Intraoperative OCT during DMEK was performed in 26 eyes of 26 patients. We retrospectively analyzed imaging and video data. SETTING Department of Ophthalmology, University of Cologne. PARTICIPANTS Seven men and 19 women aged 39 to 93 years with corneal endothelial dysfunction undergoing DMEK. EXPOSURE Descemet membrane endothelial keratoplasty. MAIN OUTCOMES AND MEASURES Visibility of surgical steps, overall duration of DMEK, overall time for complete intraoperative air filling of the anterior chamber, and correlation between donor age and Descemet rolling behavior. RESULTS Intraoperative OCT enables visualization of all steps of the DMEK procedure. Overall mean (SD) duration of the DMEK procedure was 25.7 (6.9) minutes when using iOCT. Overall mean (SD) complete intraoperative anterior chamber air-filling time was 236 (108) seconds in contrast to 60 to 90 minutes for standard air-filling time. Descemet membrane rolling behavior showed significant inverse correlation between donor age (range, 39-93 years) and the extent of rolling (R2 = 0.5 [P = .006]). CONCLUSIONS AND RELEVANCE Intraoperative OCT enhances the visibility of graft orientation and unfolding, thereby improving safety of the DMEK procedure. Overall, iOCT is a helpful device that may support surgeons in all steps of DMEK procedures.

Changes in function and morphology of normal human skin: evaluation using optical coherence tomography.

Background  Optical coherence tomography (OCT) is a noninvasive morphological method for investigating human skin. It allows high‐resolution in vivo imaging of inflammatory skin diseases and tumours. Because it is a newly developed method, systematic studies on standardization and on evaluation of factors influencing the representation of the skin have not yet been performed.

Optimising deep anterior lamellar keratoplasty (DALK) using intraoperative online optical coherence tomography (iOCT)

Background/aims To describe the use of intraoperative online optical coherence tomography (iOCT) for improving deep anterior lamellar keratoplasty (DALK) surgery. Methods Retrospective case series of 6 eyes of 6 male patients with keratokonus, corneal dystrophy or herpetic stromal scars undergoing DALK were investigated using intraoperative optical coherence tomography and postsurgical image/video analysis. Main outcome measures were: visibility of surgical steps, especially, assessment of placement depth of injection needle, preparation of bare Descemets membrane and drainage of interface fluid. Results iOCT enables real-time visualisation of all surgical steps of DALK procedure in all patients. Placement of air injection needle above Descemets membrane was reliably monitored as was presence of bare Descemets membrane and potential interface fluid. Conclusions iOCT assists with visualisation of injection needle placement and with assessment of bare Descemets membrane as well as interface fluid during the DALK procedure. Overall iOCT may be a helpful device that supports surgeons in all steps of DALK procedure.

Optische Kohärenztomographie der Kornea und des vorderen Augenabschnitts

Ziel: Die Methode der optischen Kohärenztomographie (OCT) wurde bezüglich ihrer Eignung zur Vermessung des vorderen Augenabschnitts, der Kornea und thermischer Gewebeschädigungen untersucht. Beispielhaft wurden hierzu im Rahmen der Laserthermokeratoplastik (LTK) die Veränderungen der Hornhautdicke durch die Bestrahlung sowie die induzierten thermischen Läsionen vermessen.Material und Methoden: Mit dem von uns entwickelten experimentellen Scanning-OCT wurden mit einer optischen Auflösung von ca. 20 µm axial und 25 µm lateral x-z-Schnitte des vorderen Augenabschnitts vorgenommen. Als Modellauge dienten frisch enukleierte, tonisierte Schweineaugen. Thermische Läsionen wurden mit einer kontinuierlich emittierenden Laserdiode (λ = 1,86 µm) und verschiedenen Bestrahlungsparametern appliziert. Vor und nach Koagulation wurden die Hornhaut von Limbus zu Limbus in einem zentralen OCT-Schnittbild dargestellt sowie die einzelnen Koagulationsherde vermessen.Ergebnisse: Globale und lokale Hornhautdickenänderungen sowie der Abstand Hornhaut-Linse lassen sich mit hoher Genauigkeit bestimmen. Thermische Läsionen sind in ihren Ausdehnungen klar darstellbar und zeigen gute Übereinstimmungen mit histologischen Schnittbildern, sind jedoch aufgrund der optischen Auflösung an ihren Rändern nicht so scharf abgegrenzt, wie von histologischen Präparaten bekannt.Schlußfolgerung: Mit der Methode der OCT lassen sich in vitro und, mit reduzierter Auflösung, auch in vivo quantitative Vermessungen des vorderen Augenabschnitts vornehmen. Aufgrund der qualitativ guten Übereinstimmung des Ausmaßes thermischer Schädigungen der Hornhaut mit der histologischen Morphometrie läßt sich dieses Meßverfahren auch klinisch nach LTK zur Kontrolle der Ausdehnung und Denaturierungstiefen von Koagulationen sowie zur Untersuchung des individuellen Heilungsverlaufs verwenden.Target: The method of optical coherence tomography (OCT) was investigated regarding its suitability and limits for measuring the cornea and the anterior segment of the eye. Furthermore, the stromal expansion of thermally induced lesions in the cornea directly after irradiation was determined within the scope of the laser thermokeratoplasty (LTK).Material and methods: With the experimental scanning OCT system, x-z sections of the anterior eye segment were made with an optical resolution of about 20 µm axially and 25 µm laterally. Freshly enucleated, tonicized porcine eyes were used as model eyes. Thermal lesions were applied with a continuously emitting laser diode (λ = 1.86 µm) and various radiation parameters. Before and after coagulation, the cornea was viewed from limbus to limbus in a central OCT scan and the individual coagulation source was measured.Results: Global and local changes of the thickness of the cornea as well as the distance between cornea and lens were measured with high precision. Thermal lesions in their expansion can be clearly presented and matching well with the histologically stained sections, but are not as exactly defined at the edges due to the limited optical resolution, as known from histological preparations.Conclusion: With the OCT method quantitative measuring of the anterior eye segment can be performed in vitro and with reduced resolutions also in vivo. Due to the qualitatively good correspondence regarding the dimensions of thermal damage of the cornea with histologically obtained morphometric results, this method can be used for supervision of coagulation directly after LTK as well as for examination of the individual healing process.

Intra-operative application of optical coherence tomography with an operating microscope

OBJECTIVE To introduce the use of optical coherence tomography with an operating microscope for intra-operative evaluation of the human larynx. METHODS A specially equipped operating microscope with integrated spectral domain optical coherence tomography apparatus was used during microlaryngoscopy. RESULTS Technical improvements in optical coherence tomography equipment (e.g. pilot beam, variable focal distance, improved image quality and integration into an operating microscope) have enabled greater sensitivity and imaging speed and a non-contact approach. Spectral domain optical coherence tomography now enables a better correlation between optical coherence tomography images and histological findings. With this new technology, the precision of biopsy can be improved during microlaryngoscopy. CONCLUSIONS Use of this new optical coherence tomography technology, integrated into an operating microscope, enables the surgeon to define the biopsy site location and resection plane precisely, while the optical zoom of the operating microscope can be used over the complete range.

Optical coherence tomography as an orientation guide in cochlear implant surgery

Conclusion: With optical coherence tomography (OCT) it is basically possible to reveal parts of the cochlear morphology without opening its enveloping membranes. Thus, it may serve as a helpful guide for the surgeon to localize the scala tympani precisely before opening the fluid-filled inner ear to insert the electrode array. Objective: To improve anatomical orientation in cochlear implant surgery before definitively opening the fluid-filled inner ear. The question was whether a new imaging technique, OCT, might provide information about the site of the underlying inner ear structures (scala tympani, scala vestibuli) and could, consequently, guide the surgeon towards the scala tympani. Materials and methods: In a preliminary study, OCT was carried out on human temporal bone preparations, in which a cochleostomy (‘fenestration’) was performed leaving the endosteum and the fluid-filled inner ear intact. OCT was applied via a prototype of a specially equipped operating microscope. The mode of OCT used in this context was spectral-domain (SD)-OCT. Results: On scans, which can be read analogous to B-mode sonography, OCT provides information about structures on the inner surface of the partly exposed but still intact membranous cochlear lining – such as scala tympani or scala vestibuli.

Optical coherence tomography with online visualization of more than seven rendered volumes per second

Nearly real-time visualization of 3-D volumes is crucial for the use of optical coherence tomography (OCT) during microsurgery. With an ultrahigh speed spectral domain OCT coupled to a surgical microscope, on-line display of 7.2 rendered volumes at 87 megapixels per second is demonstrated. Calculating the A-scans from the spectra is done on a quad-core personal computer (PC), while dedicated software for the 3-D rendering is executed on a high performance video card. Imaging speed is practically only limited by the readout of the camera. First experiments show the feasibility of real-time 3-D OCT for guided interventions.

Combining Optical Coherence Tomography (OCT) with an Operating Microscope

Optical coherence tomography (OCT) is an emerging biomedical imaging technology which gives high-resolution sectional images of light scattering tissue down to a depth of a few millimeter. The objective of this work is to combine OCT with an operation microscope. A spectral domain OCT was adapted via a specially designed scanning optics to the camera port of an operation microscope. This enables a non-contact on-line OCT during different medical applications. Hidden tissue structures were visualized with a resolution below 30 µm. As a first example for an application in otolaryngology we demonstrated that the OCT operation microscope is basically able to reveal parts of the cochlear morphology without opening its enveloping membranes. Thus it may serve as a helpful guide for the surgeon to exactly localize the scala tympani before opening the fluid-filled inner ear for inserting the electrode array of cochlear implants.

Optical coherence tomography allows for the reliable identification of laryngeal epithelial dysplasia and for precise biopsy: a clinicopathological study of 61 patients undergoing microlaryngoscopy.

A newly developed microscope‐based spectral‐domain optical coherence tomography (SD‐OCT) device and an endoscope‐based time‐domain OCT (TD‐OCT) were used to assess the inter‐rater reliability, sensitivity, specificity, and accuracy of benign and dysplastic laryngeal epithelial lesions.