Among other things, one or more techniques and/or systems are described for setting a sampling frequency for a radiation imaging system. The radiation imaging system comprises a rotating gantry configured to rotate a radiation source and a detector array about an object to generate an image(s) of the object. A data acquisition system is configured to sample the detector array as views. One or more flag structures are arranged according to a partial arc segment (e.g., a structure less than a full 360 degree circle). One or more sensors are disposed on one of the rotating gantry or a stationary support about which the rotating gantry rotates. When a sensor encounters a flag structure, a current rotational speed of the rotating gantry is determined. A clock frequency is updated based upon the current rotational speed to establish a sampling frequency for the data acquisition system for sampling the detector array.