Mikro-Computertomographie von Blutgefäßen parenchymatöser Organe und von Lungenalveolen

Zusammenfassung

Die Mikro-Computertomographie (µCT) dient der dreidimensionalen Bildgebung, Strukturanalyse und Morphometrie biologischer Gewebe. Dieser Artikel gibt einen Überblick über die Weiterentwicklung der Technik, die anfangs nur in der Osteoporoseforschung eingesetzt wurde, für die Visualisierung von Blutgefäßen und Parenchymstrukturen in verschiedenen Organen und über die von uns angewandten Methoden der Kontrastverstärkung. Mittels µCT lassen sich quantitative Aussagen über die Morphologie und die Zusammensetzung von Plaques in der Arterienwand gewinnen, die der lichtmikroskopischen Morphometrie ebenbürtig sind. Anhand unterschiedlicher Dichtewerte kann die µCT zwischen fibrösen Plaques, kalzifizierten Läsionen, Fibroatheromen und lipidreichen Läsionen differenzieren. In der Niere macht die µCT nach Kontrastmittelfüllung der Arterien die Glomerula der Rinde und die Vasa recta des Marks sichtbar. In der Plazenta können Blutgefäße von 2 mm Durchmesser (Arterien der Chorionplatte) bis zu 14 µm Durchmesser (terminal loop) dreidimensional erfasst und quantitativ ausgewertet werden. Zur Visualisierung des Lungenparenchyms mittels µCT ist es erforderlich, die Alveolen zu entfalten und die Strahlenabsorption der dünnen Alveolenwände zu erhöhen. Zwei Präparationsmethoden werden beschrieben: (1) Fixierung von humanem Lungengewebe mit Formalindampf und Kontrastverstärkung mit Silbernitrat; (2) intravenöse Injektion eines Gemisches aus Bariumsulfat, Gelatine und Thymol in vivo beim final narkotisierten Versuchstier. Die Mikroarchitektur des Lungenparenchyms ist mit beiden Methoden zu erfassen.

Abstract

Micro-CT has become a powerful technique in non-destructive 3D imaging and morphometric analysis. First results were limited to the investigation of osteoporosis in cancellous bone. But the availability of systems with almost microscopic resolution and sufficient soft tissue contrast has opened up entirely new applications for laboratory investigation of blood vessels and soft tissues. This article gives an overview of micro-CT technology and the potential of three-dimensional imaging of the vessel wall and soft-tissue architecture imaging in different organs using different contrast perfusion and staining techniques. Micro-CT provides quantitative information on human plaque morphology equivalent to histomorphometric analysis. Based on differences in grey-scale attenuations, micro-CT also correctly identifies atherosclerotic lesions that are histologically classified as fibrous plaques, calcified lesions, fibroatheroma, and lipid rich lesions. Micro-CT is a promising method to visualize the architecture of the renal vasculature and, importantly, to separate cortex and medulla for the visualization of glomeruli and their afferent and efferent arterioles. Micro-CT can determine the vascular surface in a defined placental volume. Combining of micro-CT data and total placental volume enables an estimation of the approximate surface of the placental vasculature. The diameter of opacified vessels in the investigated samples ranged from 2 mm (chorion plate artery) to 14 µm (smallest vessel diameter, terminal loop). Recognizing that lung parenchyma can only be visualized if the alveoli are completely expanded and the contrast of the thin alveolar walls is enhanced, we tested two preparation methods: (1) fixation of lung tissue with formalin vapour and staining with silver nitrate, and (2) intravenous injection of a barium sulfate-gelatine-thymol mixture in vivo in the anesthetized animal. We evaluated the ability of this mixture to enter the pulmonary microcirculation and the technical feasibility of micro-CT to assess lung micro-architecture.

Key words

Micro-CT - 3D-Imaging - vasculature - perfusion - detailed pulmonary structure

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