Program Information
A Comparison of Surface Dose Values Using Radiochromic Film Measurements and Treatment Plans Calculated with Different Calculation Algorithms
I Kaptan1*, Y Akdeniz1 , B Ispir1 , G Ugurluer2 , M Serin2 , (1) Acibadem Adana Hospital, Adana ,(2) Acibadem University Faculty of Medicine, Adana,
Presentations
MO-RPM-GePD-J(B)-2 (Monday, July 31, 2017) 3:45 PM - 4:15 PM Room: Joint Imaging-Therapy ePoster Lounge - B
Purpose: Accurate modelling of the surface dose has great importance in radiotherapy for clinical evaluation.The aim of this study was to test reliability of the calculation algorithms used in Eclipse TPS (version 13.6) by comparing surface dose calculations with radiochromic film measurements.
Methods: Varian Trilogy linac with 6 MV photon beams were used in this study.3D conformal radiotherapy (3DCRT), intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) treatment plans were created and calculated on the TPS. The calculation algorithms were analytical anisotropic algorithm (AAA), acuros XB (AXB) and pencil beam convolution (PBC) algorithm. The two-dimensional dose distributions of the calculated plans were exported from the TPS. Furthermore, radiochromic film calibration was made before comparing TPS calculations and radiochromic film measurements. The exported dose distribution resolution and scan resolution of the radiochromic films had the same resolution value “72 dpi”. Treatment plans were irradiated on the radiochromic films using PTW head and neck phantom. Irradiated radiochromic films were compared with exported dose distribution by Film QA. Pro. software. The datas were analyzed statistically by using IBM SPSS (version 20) software.
Results: Each calculation algorithms underestimated the surface dose in the 3DCRT, IMRT and VMAT treatment plans. It was observed that AAA was the closest one of the radiochromic film measurements between calculation algorithms.In 3DCRT treatment plans AAA 8.04%, AXB 8.66%, PBC 9.79%; in VMAT plans AAA 10.18%, AXB 12.92%; in IMRT plans AAA 6.58%, AXB 7.25%, PBC 11.88% underestimated the surface dose when they compared the radiochromic film measurements. When the results analyzed statistically, it was observed that they were statistically significant (p≤0,001).
Conclusion: Our study showed that all algorithms couldn`t model the surface dose accurately. In clinical use, we should take into consideration the patient surface dose.
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