Method to trace capillary networks in thick specimens using confocal microscopy

A method to record the capillary networks in glomeruli and lungs has been developed. This method includes a new technique for recording the specimen and new algorithms for analysis of the recorded volumes. When recording a dense specimen, the usefully attainable depth is often limited by absorption and scattering by material above the plane of focus. We found this to be a problem when studying lung and kidney tissue. A solution based on successive recording and removal of material from the specimen was developed which enabled the recording of thick layers (several hundred microns). Using a custom-made milling device, we recorded datasets of both lungs and kidneys. We then traced the capillary networks using a seed algorithm that reduces the risk of bleeding out into space not belonging to the region being filled. With this method the understanding of the specimen structure is greatly enhanced, and quantitative data can be collected from the capillary networks.