Optimization of CCD-based energy-modulated x-ray microtomography

Employing asymmetric Bragg reflection at the monochromator we obtain a wide and practically parallel synchrotron-radiation beam which, when combined with the use of a CCD detector, enables us to perform chemically specific, high-speed and high-resolution tomography. We present recent results obtained with this new method. The actual resolution achieved was determined from the measured line-spread function of the complete detection system which includes the CCD, the fluorescent screen, and the lens used for optical magnification. The modulation-transfer function (MTF) calculated from the line-spread function shows that with only twofold magnification and at 3% contrast detectability about 28 line pairs per mm are resolved. Extrapolating from this result we find that with an optical magnification of 7:1 about 100 line pairs per mm should be resolved. Ways to optimize the method further are discussed.