Interventional radiologists and staff members, during all their professional activities, are frequently exposed to protracted and fractionated low doses of ionizing radiation. The authors present a novel approach to perform on line monitoring of the staff during their interventions by using a device based on an Active Pixel Sensor (APS). The performance of the sensor as an X-ray radiation detector has been evaluated with a proper experimental set-up: the number of photons and the generated charge have been assessed as dosimetric observables. The correlation of these observables with the dose measured by the passive dosimeters has been analyzed: a good linearity has been demonstrated and the response difference between pulsed and continuous operational modes is reduced to less than 10 %, marking a distinct improvement with respect to commercial Active Personal Dosimeters.