Alexander Krüger

Effects of axial, transverse, and oblique sample motion in FD OCT in systems with global or rolling shutter line detector

This study deals with effects on the interference signal caused by axial, transverse, and oblique motion in spectrometer-based Fourier-domain optical coherence tomography (FD OCT). Two different systems are compared-one with a global shutter line detector and the other with a rolling shutter. We present theoretical and experimental investigations of motion artifacts. Regarding axial motion, fringe washout is observed in both systems, and an additional Doppler frequency shift is seen in the system using a rolling shutter. In addition, both systems show the same SNR decrease as a result of a transversely and obliquely moving sample. The possibility of flow measurement by using the decrease in signal power was demonstrated by imaging 1% Intralipid emulsion flowing through a glass capillary. This research provides an understanding of the SNR degradation caused by sample motion and demonstrates the importance of fast data acquisition in medical imaging.

Investigation of murine Vasodynamics by Fourier Domain Optical Coherence Tomography

In vivo imaging of blood vessels obtain useful insights in characterizing the dynamics of vasoconstriction and vasodilation. Fourier domain optical Coherence Tomography (FD-OCT) imaging technique permits in vivo investigation of blood vessels in their anatomical context without preparation traumata by temporal resolved image stacks. OCT is an optical, contact less imaging technique based on Michelson interferometry of short coherent near infrared light. Particularly by the possibility of a contact-less measurement and the high axial resolution up to 10 microns OCT is superior to an investigation by ultra sound measurement. Furthermore we obtain a high time resolution of vessel dynamic measurements with the used Fourier domain OCT-system by a high A-scan rate [1,22kHz]. In this study the model of saphenous artery was chosen for analyzing function and dynamics. The arteria saphena in the mouse is a suitable blood vessel due to the small inner diameter, a sensitive response to vasoactive stimuli and an advantageous anatomically position. Male wild type mice (C57BL/6) at the age of 8 weeks were fed control or high-fat diet for 10 weeks before analyzing the vasodynamics. The blood vessel was stimulated by dermal application of potassium to induce vasoconstriction or Sodium-Nitroprusside (SNP) to induce vasodilation. The morphology of the a. saphena and vein was determined by 3D image stacks. Time series (72 seconds, 300x512 pixel per frame) of cross-sectional images were analysed using semi automatic image processing software. Time course of dynamic parameters of the vessel was measured.

In vivo Three-Dimensional Fourier Domain Optical Coherence Tomography of Subpleural Alveoli Combined with Intra Vital Microscopy in the Mouse Model

Simultaneous Fourier domain optical coherence tomography and dark-field intravital video microscopy were used for in-vivo imaging of alveolar dynamics in the ventilated mouse. Quantification of the images revealed an alveolar expansion with increased end-inspiratory-pressure.

Measurement of the Epidermal Thickness with Fourier Domain Optical Coherence Tomography in an Occupational Health Study on Natural Sun Protection of the Human Skin

Fourier domain optical coherence tomography (FD-OCT) was used to take cross-sectional images of the skin at the forehead, back of hand and back of volunteers. The aim of the occupational health study was the investigation of the natural sun protection of outdoor workers and in particular the quantification of the UV induced epidermal thickening. A set of manually segmented OCT images was used as a gold standard to evaluate the performance of automatic algorithms for finding the epidermal thickness. The established A-scan averaging method and two newly developed automatic algorithms were compared. The first of the new methods is based on Markov random chains and the second new and best performing algorithm is based on a convolution filter with a trace finding routine with a quadratic cost function. Although the results of all algorithms differ in the absolute values for the epidermal thickness, they all show the same tendencies. There is a strong dependency of epidermal thickness on skin site, a weak dependency on the season of the year and a noticeable epidermal thickening 7 days of recovery after UV induced erythema.

Establishment of an Optical Imaging Device for Intraoperative Identification of Active Brain Areas

Intraoperative optical imaging in neurosurgery has the potential to reduce morbidity during tumour resection. This method for identifying active functional areas of the cortex has been tested experimentally. In this work an equipment configuration for intraoperative use of optical imaging was developed. On the basis of phantom tests parameters for intraoperative data acquisition were determined. First clinical tests during tumour resection show that it is possible to acquire significant information with high spatial resolution about the activation of cortical tissue.

(Teil-)Automatisierung der liquid-overlay-Sphäroidkultivierung

Abstract3D tumor spheroid models are increasingly applied in secondary, cellbased drug testing due to certain therapy-relevant in vivo-like characteristics. Automation of routine and delicate steps in spheroid culturing and processing, including the gentle well-to-well transfer of spheroids, facilitates spheroid-based assay standardization. Semi-automated workflows minimize experimental variations and are recommended in particular for combination treatment testing and long-term monitoring.

Abstract 5341: GlioMath-DD: A multidisciplinary approach to study glioma evolution and identify targets for individualized therapies

Glioblastoma multiforme (GBM) is the most prevalent malignant primary brain tumor in adults. GBM is classified as primary if it is assumed to have arisen de novo or as secondary if it progressed from lower grade astrocytoma. Previous studies have found that primary and secondary GBMs have distinct molecular and mutational profiles. Both have a grim prognosis with survival times of about a year with therapy. Although much progress in delineating the temporal order of mutations and copy number aberrations in the progression of lower grade gliomas was made in the past years, none of the studies have actively followed individual tumors through their progression. Whereas this method can detect aberrations that are prevalent in gliomas, it can miss events that are important in a subset of gliomas or are necessary for progression. The GlioMath-DD consortium is an interdisciplinary collaboration of several groups at the Technische Universitat Dresden (TU-Dresden) aiming to study the progression of gliomas and to come up with a mathematical model for gliomagenesis. The work involves analyzing pairs of gliomas obtained from patients who had presented with a low grade glioma and who later had a recurrence of a higher grade glioma. All tumors were checked by pathologists and then high quality DNA and RNA material extracted and used for analysis. The tumors are analyzed for copy number variations (CNV) by array comparative genome hybridization (aCGH), while gene expression changes and small mutations are analyzed using high-throughput sequencing (RNA- and Exome-seq). The data gleaned from these experiments and from in vitro models of cell growth and spheroid formation will be used by bioinformaticians and mathematicians to infer key signaling networks and formulate a mathematical model of glioma progression. The ultimate aim of this work that spans two and a half years is to create a comprehensive model of glioma promotion and progression. Furthermore, it will pinpoint driver mutations and aberrations that contribute to this progression and eventually isolate biomarkers for diagnosis and therapy. During the conference, we will present preliminary genetic data of our ongoing study. Acknowledgements: The GlioMath-DD project (coordinator: Andreas Deutsch; SAB-Number 100098214) is funded by the European Social Fund (ESF) and the Free State of Saxony Citation Format: Evelin Schrock, Khalil Abou-El-Ardat, Ralf Wiedemuth, Michael Seifert, Alvaro Kohn-Luque, Mirjam Ingargiola, Kristin Stirnnagel, Alexander Kruger, Wolfgang Nagel, Kathrin Geiger, Andreas Beyer, Leoni A. Kunz-Schughart, Gabriele Schackert, Achim Temme, Barbara Klink, Andreas Deutsch. GlioMath-DD: A multidisciplinary approach to study glioma evolution and identify targets for individualized therapies. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5341. doi:10.1158/1538-7445.AM2014-5341

Vasodynamics of the Murine Arteria Saphena by Optical Coherence Tomography

To investigate the pathogenesis of arteriosclerosis and its negative effects on the vasodynamics, in vitro experiments on isolated blood vessels as well as in vivo experiments are essential. The isometric force measurement commonly used to analyse the vasoconstriction of isolated blood vessels can not be applied in the in vivo situation. In contrast Optical Coherence Tomography (OCT) allows the acquisition of 2D cross sectional images und 3D cross sectional image stacks of vessel sections. We demonstrate that our two Fourier domain OCT-systems with their automated image analysis are suitable investigative tools for studying the stage of arteriosclerotic plaque formation as well as for examining the response of the blood vessel to vasomotor stimuli in the mouse model.

Determination of Alveolar Geometry by Optical Coherence Tomography to Develop a Numerical Model of the Fluid Dynamics in the Pulmonary Acinus

In this feasibility study a Fourier domain optical coherence tomography (FDOCT) system was used for 3D imaging of sub pleural lung parenchyma in the ventilated and perfused isolated rabbit lung. A series of 3D OCT images during a stepwise increase of pulmonary airway pressure was acquired. Refocusing and repositioning of the OCT scanner head allowed follow the volume changes of a single partial acinus of the lung.