A monolithic active pixel dosimeter, provided with at least a sensing cell, having at least a junction sensing element. The junction sensing element includes a sensing region, having a first type of conductivity, and a charge collecting region, contiguous to the sensing region and having a second type of conductivity. The sensing cell further includes an ohmic region at least partially overlapping and extending laterally outside the charge collecting region, and an annular insulating region, abutting the ohmic region, so as to form an insulating junction surrounding both the ohmic region and the charge collection region.