Imaging of human brain tumor tissue by near-infrared laser coherence tomography.

INTRODUCTION: Intraoperative detection of residual tumor remains an important challenge in surgery to treat gliomas. New developments in optical techniques offer non-invasive high-resolution imaging that may integrate well into the workflow of neurosurgical operations. Using an intracranial glioma model, we have recently shown that time domain optical coherence tomography (OCT) allows discrimination of normal brain, diffusely invaded brain tissue, and solid tumor. OCT imaging allowed acquisition of 2D and 3D data arrays for multiplanar analysis of the tumor to brain interface. In this study we have analyzed biopsy specimens of human brain tumors and we present the first feasibility study of intraoperative OCT and post-image acquisition processing for non-invasive imaging of the brain and brain tumor. METHODS: We used a Sirius 713 Tomograph with a superluminescence diode emitting light at a near infrared central wavelength of 1,310 nm and a coherence length of 15 microm. The light is passed through an optical mono mode fiber to a modified OCT adapter containing a lens system with a working distance of 10 cm and an integrated pilot laser. Navigation-registered tumor biopsies were imaged ex vivo and the intraoperative site of optical tissue analysis was registered by marker acquisition using a neuronavigation system. RESULTS: Optical coherence tomography non-contact measurements of brain and brain tumor tissue produced B-scan images of 4 mm in width and 1.5-2.0 mm in depth at an axial and lateral optical resolution of 15 microm. OCT imaging demonstrated a different microstructure and characteristic signal attenuation profiles of tumor versus normal brain. Post-image acquisition processing and automated detection of the tissue to air interface was used to realign A-scans to compensate for image distortions caused by pulse- and respiration-induced movements of the target volume. Realigned images allowed monitoring of intensity changes within the scan line and facilitated selection of areas for the averaging of A-scans and the calculation of attenuation coefficients for specific regions of interest. CONCLUSION: This feasibility study has demonstrated that OCT analysis of the tissue microstructure and light attenuation characteristics discriminate normal brain, areas of tumor infiltrated brain, solid tumor, and necrosis. The working distance of the OCT adapter and the A-scan acquisition rate conceptually allows integration of the OCT applicator into the optical path of the operating microscopes. This would allow a continuous analysis of the resection plain, providing optical tomography, thereby adding a third dimension to the microscopic view and information on the light attenuation characteristics of the tissue.

Optical coherence tomography for experimental neuroendoscopy.

Optical coherence tomography (OCT) is a non-invasive and non-contact imaging technology that has been applied to several biomedical applications. We have recently demonstrated that OCT allows discrimination of tumor adjacent brain, diffuse and solid tumor tissue and that this technology may be used to detect residual tumor within the resection cavity during resection of intrinsic brain tumors. Here we show that an OCT integrated endoscope can image the endoventricular anatomy and other endoscopically accessible structures in a human brain specimen. A Sirius 713 optical coherence tomography device was mounted to a modified rigid endoscope. A formalin-fixed human brain specimen was used to simulate endoscopic visualization of brain anatomy and two specimens of fixed malignant tumors with endoventricular growth patterns. Simultaneous OCT imaging and endoscopic video imaging of the visible spectrum was possible using a graded index rod endoscope. OCT imaging of a human brain specimen in water allowed an in-depth view into structures like the walls of the ventricular system, the choroid plexus or the thalamostriatal vein. OCT further allowed imaging of structures beyond tissue barriers or opaque media. In this fixed specimen OCT allowed discrimination of vascular structures down to a diameter of 50 mum. In vessels larger that 100 mum the lumen could be discriminated and within larger blood vessels a layered structure of the vascular wall as well as endovascular plaques could be visualized. This in vitro pilot study has demonstrated that OCT integrated into neuroendoscopes may add information that cannot be obtained by the video imaging alone. This technology may provide an extra margin of safety by providing cross-sectional images of tissue barriers within optically opaque conditions.

Time-domain and spectral-domain optical coherence tomography in the analysis of brain tumor tissue.

INTRODUCTION: Detection of residual tumor during resection of glial brain tumors remains a challenge because of a low inherent contrast of adjacent edematous brain, the surrounding infiltration zone, and the solid tumor. Therefore, new technologies that may facilitate an intraoperative analysis of the tissue at the resection edge are of great interest to neurosurgeons. MATERIALS AND METHODS: For ex vivo imaging of gliomas in a mouse model and human biopsy specimens of brain tumors and nervous system tissue we have used a time-domain Sirius 713 Tomograph with a central wavelength of 1,310 nm and a coherence length of 15 microm equipped with a mono mode fiber and a modified optical coherence tomography (OCT) adapter containing a lens system for imaging at a working distance of 2.5 cm. A spectral-domain tomograph using 840 nm and 930 nm superluminescence diodes (SLD) with a central wavelength of 900 nm was used as a second imaging modelity. RESULTS: Both time-domain and spectral-domain coherence tomography delineated normal brain, the infiltration zone and solid tumor in murine intracerebral gliomas. Histological evaluation of H&E sections parallel to the optical plain demonstrated that tumor areas of less than a millimeter could be detected and that not only solid tumor, but also brain invaded by a low-density single tumor cells produced an OCT signal different from normal brain. Spectral-domain OCT (SD-OCT) demonstrated a significantly more detailed microstructure of tumor and normal brain up to a tissue depth of 1.5-2.0 mm, whereas the interpretation of time-domain OCT (TD-OCT) was difficult at a tissue depth >1.0 mm. Because of rapid scanning times SD-OCT data could be acquired as 3D data maps, which allowed a multi-planar analysis of the tumor to brain interface. Similar to our findings in experimental gliomas, images of human nervous system tissue acquired using SD-OCT showed a characteristic signal of normal brain tissue and a detailed microstructure of tumor parenchyma. CONCLUSION: Spectral-domain OCT of experimental gliomas and human brain tumor specimens differentiates solid tumor, diffusely invaded brain tissue, and adjacent normal brain based on microstructure and B-scan signal characteristics. In conjunction with the rapid image acquisition rates of SD-OCT, this technology carries the potential of a novel intraoperative imaging tool for the detection of residual tumor and guidance of neurosurgical tumor resections.

Detection of an X-Ray Hot Region in the Virgo Cluster of Galaxies with ASCA.

Based on mapping observations with ASCA, an unusual hot region with a spatial extent of 1 deg2 was discovered between M87 and M49 at a center coordinate of R.A.=12h27m36s and decl.=9&j0;18' (J2000). The X-ray emission from the region has a 2-10 keV flux of 1x10-11 ergs s-1 cm-2 and a temperature of kT greater, similar4 keV, which is significantly higher than that in the surrounding medium of approximately 2 keV. The internal thermal energy in the hot region is estimated to be VnkT approximately 1060 ergs with a gas density of approximately 10-4 cm-3. A power-law spectrum with a photon index of 1.7-2.3 is also allowed by the data. The hot region suggests there is an energy input due to a shock that is probably caused by the motion of the gas associated with M49, infalling toward the M87 cluster with a velocity greater, similar1000 km s-1.

[Significance of blood Ca(++) determination for assessment of the current status of calcium homeostasis]. / Die Bedeutung der Blut-Ca(++)-Bestimmung für die Einschätzung des aktuellen Zustandes der Calciumhomöostase.

Out of the blood calcium fractions know only the ionized calcium is biologically active. From the height of the total calcium level despite significant dependence no secure conclusion to the Ca++ concentration can be drawn. The level of the total calcium spreads further than that one of the ionized calcium. The up to now used mathematical approaches for the estimation of the blood Ca++ concentration also proved unsuitable; none of them provides a really better statement than the total calcium level. Thus even they represent no acceptable alternative to the Ca++ determination by means of ion-selective electrodes. The investigation by means of ion-selective electrodes. The investigation of various paraclinical sizes (total calcium, total protein, albumin, creatinine, alkaline phosphatase) in a group of patients and a control group in quality and quantity resulted in a different influence on the Ca++ level by the influential factors tested. Only by measurement of the ionized calcium the real actual condition of the calcium homoeostasis can be reflected. Therefore it is no more justified to draw diagnostically and therapeutically relevant consequences from the exclusive determination of the total calcium level.

Effect of gravity on lymphocyte proliferation.

Reports on postflight examination of lymphocytes from crew members of soviet and american spaceships show a depression of reactivity towards mitogens in vitro. The purpose of this communication is to present experimental evidence that gravity can interfere with lymphocyte activation. Lymphocytes were incubated in the presence of concanavalin A in a centrifuge at 2 and 4 g for four days. This environment causes a significant acceleration of the response to the mitogen. In addition, remarkable differences in the ultrastructure of cells grown at 1 g and 4 g are observed by electron microscopy. This investigation is related to the experiment "Effect of weightlessness on lymphocyte proliferation" experiment which will be performed during the first Spacelab mission.

[Radiodensitometric studies on bone structure following tooth extractions]. / Röntgendensitometrische Knoschestrukturntersuchungen nach Zahnextraktionen

Radiographs of the human mandible, accurately showing the same location, are made at different times after extraction of lateral teeth and examined with regard to changes in the bone structure during wound healing. The radiograms are evaluated by densography and the photometric graphs thus obtained are evaluated by computer. Compared with histological findings known so far, these examinations furnish information on time and location of resorption and production of bone after dental extractions. The first findings are quantitatively presented.