Program Information
Impact of Gantry and Table Angles On Proton Range in XiO Treatment Planning System
S Rana*, Y Zheng , Procure Proton Therapy Center, Oklahoma City, OK
Presentations
SU-E-T-201 Sunday 3:00PM - 6:00PM Room: Exhibit HallPurpose:To investigate if the selection of gantry and table angle has an impact on the calculated proton range (defined at the 90% distal falloff of the spread out Bragg peak) in XiO treatment planning system (TPS).
Methods:A homogenous water phantom (40x40x40 cm³) was constructed in XiO TPS. Ten treatment plans were generated using identical beam conditions (proton range = 25cm, modulation = 10cm) and device (10 cm diameter aperture) for various combinations of gantry (G) and table (T) angles (G0T90, G90T90, G180T90, G270T90, G90T0, G90T180, G90T270, G270T0, G270T180, and G270T270). The isocenter in each plan was selected at the center of the cubic target volume (5x5x5 cm³) inside the phantom. All ten plans were calculated with pencil beam algorithm using a grid size of 3mm. The calculated proton ranges in all 10 plans were then compared against the prescribed (or expected) proton range, which was 25 cm in this study.
Results: For all 10 treatment plans, calculated proton range was smaller when compared to the expected value (25cm), with XiO predicting the proton range from 24.62cm to 24.92cm. The difference between the prescribed and calculated proton range was highest (3.8mm) for plans with G90T270 and G270T90.
Conclusion:Treatment plans generated in XiO TPS using G90T270 and G270T90 could produce a difference of more than 3 mm between the prescribed and calculated proton ranges. Further study using smaller dose calculation grid size (e.g., 1mm) is under progress to determine if the dose calculation grid size has any impact on the proton range. What causes the angle dependence of proton range calculation with the XiO TPS is also under investigation.
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