Medical devices, such as imaging devices are often used in combination with many other medical devices.  These other devices are, for example, devices provided with a screen for monitoring data.  Other devices include medical instruments like injectors or support devices such as tables.  In order to operate the variety of devices in a medical room efficiently, there appears to be need to an improve tracking of the relative position of patients and staff with respect to the medical devices, during the use of such medical devices.  Regarding patients, in the prior art, it is suggested to locate the medical device with respect to the patient's bed.  This approach will have as an effect that if a patient moves on its bed, no adjustment is made with respect to the amended relative position of the medical device and the patient.  With respect to staff members, for the operation of medical devices, the relative position between the staff members and the devices is not used to improve the use of the devices.