EDR2 film dosimetry for IMRT verification using low-energy photon filters.
Recently the EDR2 (extended dose range) film has been introduced commercially for applications in radiation therapy dosimetry. In addition to characterizing the wide dynamic range, several authors have reported a reduced energy dependence of this film compared to that of X-Omatic Verification (XV) films for megavoltage photon beams. However, those investigations were performed under limited geometrical conditions. We have investigated the dosimetric performance of EDR2 film for the verification of IMRT fields at more clinically relevant conditions by comparing the film doses with the doses measured with an ion chamber and XV films. The effects of using a low energy scattered photon filter on EDR2 film dosimetry was also studied. In contrast to previous reports our results show that EDR2 film still exhibits considerable energy dependence (a maximum discrepancy of 9%, compared with an ion chamber) at clinically relevant conditions (10 cm depth for IMRT fields). However, by using the low-energy filters the discrepancy is reduced to within 3%. Therefore, EDR2 film, in combination with the filters, is found to be a promising two-dimensional dosimeter for verification of IMRT treatment fields.
Princess Margaret Hospital, University of Toronto, Toronto, Ontario M5G 2M9, Canada. medicphys@hotmail.com
Inhwan Jason
IJ
Yeo
Akbar
A
Beiki-Ardakani
Young-Bin
YB
Cho
Mostafa
M
Heydarian
Ting
T
Zhang
Mohammad
M
Islam
D019544:Equipment Failure Analysis / Q000295:instrumentation / Q000379:methods; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity