Method for ascertaining a time for a calibration, x-ray device and computer program

A control system for at least one x-ray device, the control system comprising:

• a further x-ray device;
• and
• a control device configured for performing a method for ascertaining a time for a fresh calibration for ascertaining up-to-date calibration parameters of the x-ray device, the x-ray device having multiple degrees of freedom of movement for a recording configuration containing an x-ray emitter and an x-ray detector, the method comprises the steps of:
• recording x-ray images of a calibration phantom for at least some of possible recording positions of the recording configuration;
• evaluating the x-ray images to ascertain calibration parameters allowing ascertainment of geometry parameters, describing a recording geometry, from position data of the recording configuration being based on the degrees of freedom of movement;
• ascertaining in multiple operating phases, situated between two calibrations, of the at least one further x-ray device of identical design to the x-ray device, a piece of use information containing use data describing an accumulated use of the degrees of freedom of movement during an operating phase and a piece of difference information describing a difference in the calibration parameters between the calibrations delimiting the operating phase;
• and
• determining the time for the fresh calibration from a relationship, determined by collective evaluation of all the use information, between the use data and the difference information on a basis of the use data recorded since a last calibration.