The present invention relates to a system, a method and a filler for measuring a dose of ionizing radiation received by a pre-determined part of the body during radiotherapy while creating a space between the organ to be irradiated and organs to be protected. The invention also relates to uses of such filler. The system comprises an injectable dosimetric filler, which under the influence of ionizing irradiation undergoes measurable physical and/or chemical changes, while preserving its spatial integrity a detector system for measuring the physical and/or chemical changes within the radiation sensitive filler by sending an energy wave to the radiation sensitive filler and capturing the signal emitted therefrom and a control unit for processing the signal captured by the detector system and calculating a dose of ionizing radiation previously or simultaneously received by each part of the volume of the radiation sensitive filler on the basis of said signal.
