A method to improve the accuracy of diode in vivo dosimetry for external megavoltage photon beams filtered by wedges
الموضوعات : Journal of Theoretical and Applied PhysicsAlireza Mohammadkarim 1 , Mahmoud Allahverdi 2 , Hasanali Nedaie 3 , Mahbod Esfehani 4 , Alireza Shirazi 5 , Ghazale Geraily 6
1 - Department of Medical Radiation Engineering, Science and Research Branch, Islamic Azad University
2 - Department of Medical Physics, Tehran University of Medical Sciences
3 - Department of Radiotherapy, Tehran University of Medical Sciences
4 - Radiotherapeutic Oncology Department, Cancer Institute
5 - Department of Medical Physics, Tehran University of Medical Sciences
6 - Department of Medical Physics, Tehran University of Medical Sciences
الکلمات المفتاحية: dosimetry, Diode dosimeter, Ionization chamber, Off, axis wedge correction factor,
ملخص المقالة :
AbstractDiode in vivo dosimetry is widely considered to be an important tool for quality improvement of patient care in external radiotherapy. In vivo dose measurements for wedged photon beams require correction factor estimation for difference in wedge angles and field sizes. The diode dosimeters that were used in this study were two different models of PTW products; T60010L and T60010M models were used for 60Co and 6-MV photon beams, respectively. The values of off-axis wedge correction factor were determined at two different physical situations in the wedged and non-wedged directions on the entrance surface of the polystyrene phantom. The wedge correction factor at various depths was then estimated by a proposed method. Results show that the absorbed dose at each depth can be estimated by applying accurate wedge correction factor at depth, on entrance surface dose with negligible probable errors (below 1.2%).
