The present invention relates to a dosimetry device (10) for determining a spatial distribution of a quantity of radiation incident on the dosimetry device. The device comprises a segmented electrode assembly (12) comprising an electrically non-conducting substrate (13) having a plurality of electrode elements (14) provided thereon, surrounded by ground electrodes. The device further comprises an electrically conducting sheet (16) comprising a protrusion (17) arranged such as to define a plurality of ionization chamber cavities (18) between the segmented electrode assembly (12) and the electrically conducting sheet (16). The device also comprises a voltage applying means (28) for applying a voltage difference between the electrically conducting sheet (16) and the plurality of electrode elements (14) and a routing means (25) for routing a plurality of ionization currents corresponding to the plurality of electrode elements (14) to a processing means.
