Three-dimensional imaging of nerve tissue by x-ray phase-contrast microtomography

We show that promising information about the three-dimensional (3D) structure of a peripheral nerve can be obtained by x-ray phase-contrast microtomography (p-mu CT; Beckmann, F., U. Bonse, F, Busch, and O. Gunnewig, 1997. J. Comp, Assist. Tomogr, 21:539-553), P-mu CT measures electronic charge density, which for most substances is proportional to mass density in fairly good approximation. The true point-by-point variation of density is thus determined in 3D at presently I mg/cm(3) standard error (SE). The intracranial part of the rat trigeminal nerve analyzed for the presence of early schwannoma "microtumors" displayed a detailed density structure on p-mu CT density maps. The average density of brain and nerve tissue was measured to range from 0.990 to 0.994 g/cm(3) and from 1.020 to 1.035 g/cm(3), respectively, The brain-nerve interface was well delineated. Within the nerve tissue, a pattern of nerve fibers could be seen that followed the nerve axis and contrasted against the bulk by 7 to 10 mg/cm(3) density modulation. Based on the fact that regions of tumor growth have an increased number density of cell nuclei, and hence of the higher z element phosphorus, it may become possible to detect very early neural "microtumors" through increases of average density on the order of 10 to 15 mg/cm(3) by using this method.