COMPUTED 3-DIMENSIONAL RECONSTRUCTION OF MEDIAN-EMINENCE CAPILLARY MODULES - IMAGE ALIGNMENT AND CORRELATION

Image alignment is an absolute requirement for three-dimensional (3-D) reconstruction from serial sections, and Fourier correlation is the m ost powerful way to compute alignments. The rotational and translation al components of misalignment can be corrected by an iterative correla tion procedure, but for images having significant differences, alignme nt can fail with a likelihood proportional to the extent of the differ ences. We found that translational correction was determined much more reliably when low-pass filters were applied to the product transforms from which the correlations were calculated. Rotational corrections b ased on polar analyses of the auto-correlations of the images instead of on the images directly contributed to more accurate alignments. The se methods were used to generate 3-D reconstructions of brain capillar y modules from serial-section mosaics of digitized transmission electr on micrographs.