Commissioning Enhanced Dynamic Wedges Utilizing Mapcheck Device and Comparing with Film and Ion Chamber Dosimetry
Byline
R Badkul*, C Myers, University of Kansas Medical Center, Kansas City, KS
Varian Enhanced Dynamic Wedge (EDW) is a wedge technique where no physical modifier is used to create a wedge dose profile. The wedge dose profile is created by sweeping one of the Y jaw from open to closed position while other Y jaw and the X jaws stand still throughout the treatment. Because of the collimator motion, different parts of the field are exposed to the primary beam for different lengths of time.The motion of the jaw is controlled by a computer and the dose vs. collimator relationship to be followed in treatment mode is contained in a dose vs. jaw position table called Segmented Treatment Table (STT). The EDW provides wedge angles of 10°, 15°, 20°, 25°, 30°, 45° and 60° for both symmetric and asymmetric field sizes. EDW does not cause beam hardening and extra scatter to patients as compared to physical wedges. We measured the Wedge profiles using mapcheck device which contains 445 diodes in 2D array at various depths such as Dmax, 5cm, 10cm and 20cm. Dose profiles were also measured using EDR2 film and RIT software and 0.125cc ionization chamber. Profiles were compared with TPS generated profiles. We found that profiles measured with Mapcheck device agrees well within 1-4% with film & ionchamber measurements and TPS calculations. Mapcheck device is a very useful and time saving tool for commissioning and QA of EDW wedges.
