The invention relates to detectors for radiological imaging, and more particularly the X-ray matrix detectors, produced in the form of a CMOS technology pixel matrix, associated with a structure for converting X-rays into electrons. Each pixel comprises a reading circuit comprising on the one hand a comparator (COMP1) switching over each time a charge increment arrives resulting from the integration of a charge current generated by the lighting and on the other hand a counting circuit (CPT1, CPT2) for counting the number of switchovers of the comparator. The circuit for reading each pixel comprises a circuit (CMC) for analyzing the rate of the switchovers of the comparator, this analysis circuit acting on the counting circuit to modify its operation according to the result of the rate analysis. For example, the analysis circuit switches the counting pulses to one counter (CPT1) or another counter (CPT2) depending on the result of the analysis. Applicable in particular to bi-energy radiology and X-photon impact spectrometry analysis.