Intensity modulated radiotherapy dosimetry with ion chambers, TLD, MOSFET and EDR2 film

Purpose of this study was to report in a together our experience of using ion chambers, TLD, MOSFET and EDR2 film for dosimetric verification of IMRT plans delivered with dynamic multileaf collimator (DMLC). Two ion chambers (0.6 and 0.13 CC) were used. All measurements were performed with a 6MV photon beam on a Varian Clinac 6EX LINAC equipped with a Millennium MLC. All measurements were additionally carried out with (LiF:Mg,TI) TLD chips. Five MOSFET detectors were also irradiated. EDR2 films were used to measure coronal planar dose for 10 patients. Measurements were carried out simultaneously for cumulative fields at central axis and at off-axis at isocenter plane (+/- 1, and +/- 2 cm). The mean percentage variation between measured cumulative central axis dose with 0.6 cc ion chamber and calculated dose with TPS was -1.4% (SD 3.2). The mean percentage variation between measured cumulative absolute central axis dose with 0.13 cc ion chamber and calculated dose with TPS was -0.6% (SD 1.9). The mean percentage variation between measured central axis dose with TLD and calculated dose with TPS was -1.8% (SD 2.9). A variation of less than 5% was found between measured off-axis doses with TLD and calculated dose with TPS. For all the cases, MOSFET agreed within +/- 5%. A good agreement was found between measured and calculated isodoses. Both ion chambers (0.6 CC and 0.13 CC) were found in good agreement with calculated dose with TPS.