Array tomography: high-resolution three-dimensional immunofluorescence

Array tomography, which is described in this article, is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Although the fabrication procedures can be relatively difficult, the high resolution, depth invariance, and molecular discrimination offered by array tomography justify the effort involved. Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture.