  We describe a method aiming at increasing the dynamic range of X-ray
detectors. Two X-ray exposures of an object are acquired at different dose
levels and constitute the only input data. The values of the parameters which
are needed to process these images are determined from information contained in
the images themselves; the values of two parameters are extracted from the
input data. The two input images are finally merged in such a way as to create
one image containing useful information in all its entirety. This selective use
of parts of each image allows both the contour of the irradiated object to be
visible and the high-attenuation areas to retain their image quality
corresponding to the information contained in the high-dose image. The benefits
of the method are demonstrated with an example involving a head phantom.
