Stalagmite CT scan
The movie is of a stalagmite sample (collected from the Western Pacific) which is to be sectioned for geochemical analysis. It is important that the sample is cut so that the plane follows a major growth axis or axes. However, it is not always obvious from the outside of the sample which plane to make the cut.
The sample has therefore been CT scanned at 2 mm intervals to produce a dataset consisting of 127 greyscale images (each one being a different cross-section). I wrote a routine to load these stacked datasets into a 3-dimensional matrix in Igor, and then digitised the central growth axes (using other Igor routines that I wrote).
This sample has 3 major growth axes, shown in red, green and blue. Surrounding these is a partially transparent isosurface representing the outside edge of the speleothem sample. Using the isosurface as a reference for the outside of the sample, I was able to select the optimum cutting plane from the digitised growth axes.
Dr Daniel Sinclair
Institute for Geophysics (Jackson School of Geosciences)
University of Texas in Austin