In vivo micro-CT quantification of aerated and tissue lung volume.

<p><b>A)</b> A 2D representative μCT transverse, inferior cross section of a WT lung at cervical vertebra 8 shows the margin of the lung inside of the abdominal cavity. <b>B)</b> This margin is then used with semi-automated tools in Amira to segment the lung (Blue overlay) and a 3D reconstruction can be generated (<b>C</b>). The lung is further segmented into the conducting airway (Grey, <b>C</b>) and into the left (*) and right (#) lobes for more specific analysis (<b>A-C</b>). The raw intensity values from either the whole lung segment or a smaller portion are extracted to generate intensity histograms (<b>D</b>). To delineate aerated lung volume from tissue lung volume a thresholding operation must be developed. The most abundant volume in a healthy lung is the interface between air and the alveolar epithelium. As measured by μCT, the most abundant density in 3–12 month old WT mice is -256 HU (<b>E</b>). Using this threshold, aerated and tissue lung volume can be quantified as shown in a representative 2D overlay (<b>F</b>, Green = Aerated Volume, Orange-Red = Tissue Volume, Blue = Conducting Airway) and 3D reconstructions (<b>G</b>, Aerated Volume; <b>H</b>, Tissue Volume, Blue = Conducting Airway). Note the distinct bronchiole and arteriole structures in <b>G</b> and <b>H</b>.