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.