We present a technique for correcting image artifacts caused by refractive index distributions in Scanning Laser Optical Tomography (SLOT) and Optical Projection Tomography (OPT). Projection images can be distorted due to the presence of a refractive index distribution around the sample. We consider the special case of a refractive index distribution given by a capillary around a sample. The particular application we are interested in is in vitro imaging of cell spheroids in a glass capillary. Numerical simulations and experimental results are used to illustrate the connection between the Radon transform and the refracted projection. Thereupon we will describe a technique that transforms refracted projections to parallel ray Radon projections and thus allows artifact free reconstruction within the sample volume.
Imaging of biological samples necessitates high requirements on multi modal 3D imaging techniques. Lately, the
range of application fields has extended from transparent biological samples up to biological compartments on
intransparent objects. We introduce SLOT as an innovative and highly efficient tool for multi modal visualization by
intrinsic and extrinsic contrast mechanisms in biological model organisms with sizes up to several millimeters. One
aim is the exploration of SLOTs capability to image organs of biological model organisms. Therefore, intrinsic
contrast mechanisms were addressed regarding their ability for visualizing and quantitating structural details within
the murine lung. Additionally we present SLOT as a valuable tool for the in vitro structural and volumetric large
scale investigation of biofilm formation on implants with sizes up to several millimeters.
New optical techniques have the potential to fill the gap between radiological and microscopic approaches to assess the lung's internal structure. Since its quantitative assessment requires unbiased sampling and measurement principles, imaging of the whole lung with sufficient resolution for visualizing details is important. To address this request, we applied scanning laser optical tomography (SLOT) for the three dimensional imaging of mouse lung ex vivo. SLOT is a highly efficient flourescence and transmission microscopy technique allowing for 3D imaging of specimen of sizes up to several millimeters. Previously fixed lung lobes and whole lungs were optically cleared and subsequently imaged with SLOT while making use of intrinsic contrast mechanisms like absorption and autofluorescence. Imaging of airways, blood vessels and parenchyma is demonstrated. Volumetric SLOT datasets of the lung's internal structure can be analyzed in any preferred planar orientation. Moreover, the sample preparation preserves microscopic structure of the lung and allows for subsequent correlative histologic studies. In summary, SLOT is a useful technique to visualize and survey the internal structure of mouse lung at different scales and with various contrast mechanisms. Potential applications of SLOT in lung research are e.g. quantitative phenotype analysis of mouse models of human lung disease in combination with stereological methods.
Light microscopy is one of the major tools in modern biology. The steady development of new microscopic
techniques leads to an correspondent improvement of biological methods. To expand the catalog of biological
experiments, we investigate the possibilities of optical projection tomography (OPT). This technique is based on
the already established X-Ray computed tomography. In contrast to most other three-dimensional microscopy
techniques it is able to create three dimensional data sets of the specimens natural absorption, staining and
fluorescence. Unfortunately, these advantages are opposed by a low resolution, reconstruction artifacts, and a
relatively big loss of fluorescence light. We reduced the disadvantage in resolution by applying physical filters in
the Fourier plane of the image path, which is not possible in X-Ray imaging yet.
Biocompatibility studies of percutanous implants in animal models usually involve numerous lethal biopsies for
subsequent morphometric analysis of the implant-tissue interface. A common drawback of the study protocol is
the restriction of the analysis to one final time point. In this study optical coherence tomography (OCT) was used
to visualize and enable quantification of the local skin anatomy in the vicinity of a percutaneous implant in an
animal model using hairless mice. Non invasive in vivo optical biopsies were taken on predetermined time points
after implantation and ex vivo in situ at the day of noticeable inflammation. The custom made Fourier-domain
OCT system was programmed for imaging with different scanning schemes. A spoke-pattern of 72 cross-sectional
scans which was centred at the midpoint of the circular shaped implants was acquired and worked best for the
in-vivo situation. Motion-artefact-free three-dimensional tomograms were obtained from the implant site before
excision and preparation for histology. Morphometric parameters such as epithelial downgrowth, distance
to normal growth and tissue thickness were extracted from the images with a simple segmentation algorithm.
Qualitatively, the OCT B-Scans are in good agreement with histological sections. Therefore, OCT can provide
additional valuable information about the implant-tissue interface at freely selectable time points before the
lethal biopsy. Locally confined quantitative assessments of tissue-implant interaction for in vivo postoperative
monitoring can be carried out.
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