Comparison of beam hardening effect of physical and enhanced dynamic wedges at bladder inhomogeneity using EBT3 film dosimeter
Ghazale Geraily1, Nooshin Sharafi1, Alireza Shirazi1, Mahbod Esfehani2, Maryam Masoudifar3, Blookat Eftekhar Rajab4
1 Department of Medical Physics and Medical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran
2 Cancer Institute, Imam Hospital, Tehran University of Medical Sciences, Tehran, Iran
3 Department of Radiotherapy, Mahak Hospital, Tehran, Iran
4 Department of Radiotherapy, Shohada Tajrish Hospital, Shahid Beheshti University of Medical Science, Tehran, Iran
Department of Medical Physics and Medical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran
Source of Support: None, Conflict of Interest: None
Introduction: Using physical wedges (PWs) to modify dose distribution and more homogeneous target coverage is a well-established technique. However, there are many problems with PWs known as beam hardening, which made them problematic. This can be overcome by dynamic wedges which do not filter beam. Comparison of physical properties of physical and enhanced dynamic wedges (EDWs) restricted to homogeneous medium. Hence, the main aim of this study is to compare dosimetric properties of physical and EDWs at bladder inhomogeneous phantom as a most common case implementing wedges.
Materials and Methods: An inhomogeneous pelvic phantom with homogeneities of uterus, femur, soft tissue, rectum, and bladder was designed. Eclipse treatment planning system with the aim of bladder target was used for calculations. All dose distributions were measured with EBT3 films.
Results: Comparison between beam profiles of physical and EDWs at wedged and nonwedged directions shows a greater difference at near inhomogeneous soft tissue interface and also at heel side of wedges.
Conclusion: Little difference observed between dose distribution of physical and EDWs shows neglectable effect of beam hardening produced by PW compared to EDW at inhomogeneous medium. Furthermore, EBT3 films present good feature to measure dose distributions at EDW fields.