Abstract: A apparatus for accurately measuring radiation beams during treatment which comprises a dosimeter which is used to measure the radiation; an optical marker which is used to determine the patient position; and said dosimeter and said optical marker are connected to one another used to provide and display simultaneously a radiation dose reading and a measurement of the patient's movements during treatment.

Abstract: In a dosimeter for measuring levels of ionizing radiation, for example during radiotherapy, a plurality of radiation sensors, such as insulated gate field effect transistors (IGFETs), are spaced apart at predetermined intervals on a support, for example a flexible printed circuit strip, and connected to a connector which can be coupled to a reader for reading the sensors. The sensors may each be connected to a reference device, which may also be an insulated gate field effect transistor, and the absorbed radiation dose may be determined by measuring, before and after the irradiation, the difference between the threshold voltages of the individual sensors and the threshold voltage reference device. Corresponding terminals of the sensors may be connected to the connector by a single conductor, thereby reducing the number of conductors required.