It is important to remember that the X-ray machine that your doctor uses and the X-ray detectors that NASA uses are very similar instruments.

Your doctor uses the following recipe:
An X-ray machine sends X-rays toward you. An X-ray image of counts versus position is made on film.

The astrophysicist uses the following recipe:
A neutron star (for example) sends X-rays which are detected by the PCA detector on the RXTE satellite. X-ray light curves and spectra (counts versus time and energy) are made.