Technical note: Vendor‐agnostic water phantom for 3D dosimetry of complex fields in particle therapy

PURPOSE: Three‐dimensional (3D) dosimetry is a necessity to validate patient‐specific treatment plans in particle therapy as well as to facilitate the development of novel treatment modalities. Therefore, a vendor‐agnostic water phantom was developed and verified to measure high resolution 3D dose distributions. METHODS: The system was experimentally validated at the Marburger Ionenstrahl‐Therapiezentrum using two ionization chamber array detectors (PTW Octavius 1500XDR and 1000P) with 150.68 MeV proton and 285.35 MeV/u (12)C beams. The dose distribution of several monoenergetic and complex scanned fields were measured with different step sizes to assess the reproducibility, absolute positioning accuracy, and general performance of the system. RESULTS: The developed system was successfully validated and used to automatically measure high resolution 3D dose distributions. The reproducibility in depth was better than ±25 micron. The roll and tilt uncertainty of the detector was estimated to be smaller than ±3 mrad. CONCLUSIONS: The presented system performed fully automated, high resolution 3D dosimetry, suitable for the validation of complex radiation fields in particle therapy. The measurement quality is comparable to commercially available systems.