title: The value of the LA48 linear ion chamber array for characterization of intensity-modulated beams.
abstract: In this paper the performance of the LA48 linear ion chamber array (PTW, Freiburg, Germany) for characterization of intensity-modulated (IM) beams was investigated. First, some elementary properties were explored. A series of beam penumbras and output factors for small rectangular fields were measured at 6 and 18 MV, and the results were compared with data obtained using a diamond detector. The energy and dose rate dependence of the array response were examined, and the leakage current was assessed. In a second step, profiles were measured for two clinically delivered IM beams and for a dynamic wedge. The interplay between the sharpening of the penumbra by the upper metal electrode plate of the array and the volume averaging of the 4 x 4 mm ion chamber elements results in precise measurements, even in regions of high dose gradient. It is true, however, that the metal electrodes imply a small energy spectrum dependence in the array response. The dose rate dependence is found to be negligible. All of this makes, the LA48 linear array a suitable device for analysing dose distributions of clinical IM beams.
authors.affiliation: Division of Radiotherapy, Ghent University Hospital, Gent, Belgium.
authors.forename: C
authors.initials: C
authors.lastname: Martens
authors.forename: C
authors.initials: C
authors.lastname: De Wagter
authors.forename: W
authors.initials: W
authors.lastname: De Neve
mesh_terms: D004307:Dose-Response Relationship, Radiation; D006801:Humans; D007477:Ions; D015233:Models, Statistical; D011137:Polystyrenes / Q000737:chemistry; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods*
chemical_list: D007477:Ions; D011137:Polystyrenes