FBX aqueous chemical dosimeter for measurement of virtual wedge profiles

We investigated the ferrous sulfate–benzoic acid–xylenol orange (FBX) aqueous chemical dosimeter for measurement of virtual (dynamic) wedge profiles on a linear accelerator. The layout for irradiation of the FBX‐filled tubes mimicked a conventional linear detector array geometry. A comparison of the resulting measurements with film‐measured profiles showed that, in the main beam region, the difference between the FBX system and the film system was within [Formula: see text] and that, in the penumbra region, the difference varied from [Formula: see text] to [Formula: see text] in terms of positional equivalence, depending on the size of the dosimeter tubes. We thus believe that the energy‐independent FBX dosimetry system can measure virtual wedge profiles with reasonable accuracy at reasonable cost. However, efficiency improvement is required before this dosimetry system can be accepted into routine practice. PACS numbers: 87.53.‐j, 87.53.Dq, 87.53.Mr, 87.53.Xd, 87.66.Ff