A medical radiology system comprises an external x-ray source (1) and a CMOS image sensor (2) that is connected via a USB link (4) by way of USB peripheral of a device (3) for digitally processing the image data of the sensor. A tracking device is placed on the USB link (4) in order to continuously read and decode the data transmitted over this link in a way that is transparent to the device and to the sensor, and to detect, in the transmitted data stream, one particular datum (XAMC=1) representing a signal indicating detection, by the sensor, that a sufficient dose of radiation has been received. On detection of this particular datum, the tracking device sends an electrical signal Stop-X to the radiation source, in order to stop the emission of the radiation. The system is especially suitable for taking dental radiology images with an intra-oral CMOS sensor.
