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PO-0806: Dosimetric end-to-end test procedures using alanine dosimetry in scanned proton beam therapy
S430 ESTRO 36 _______________________________________________________________________________________________
dosimetric end-to-end procedures for protons based on customized anthropomorphic phantoms and different dosimetric techniques. Material and Methods A homogeneous polystyrene phantom and two anthropomorphic phantoms (pelvis and head phantom) have been customized to allocate different detectors such as radiochromic films, ionization chambers and alanine pellets. During testing, the phantoms were moving through the workflow as real patients to simulate the entire clinical procedure. The CT scans were acquired with pre-defined scan protocols used at MA for cranial and pelvic treatments. All treatment planning steps were performed with RayStation v5.0.2 treatment planning system (TPS). A physical dose of 10 Gy was planned to clinically shaped target volumes in order to achieve uniformity better than 0.5% on the dose delivered to the alanine pellets. In the treatment room the plans were delivered to the phantoms loaded either with alanine pellets and radiochromic EBT3 films (figure 1) or two Farmer chambers. The alanine pellets (5.0 mm diameter and 2.3 mm thickness) and their read-out were provided by the National Physical Laboratory (NPL). One of the challenges of alanine for dosimetry in particle beams is the known response dependency (quenching) on the charge, the fluence and the energy of the particles constituting the mixed radiation field. Corrections for this were derived by a Monte Carlo dose calculation platform implemented in a non-clinical version of RayStation.
Conclusion The investigated beam model showed excellent agreement with measured data over a wide range of field sizes and measurement depths with improved agreement for small field sizes. These commissioning results are a solid basis for ongoing investigations focusing on more complex treatment types such as IMRT and VMAT and heterogeneous phantoms. PO-0806 Dosimetric end-to-end test procedures using alanine dosimetry in scanned proton beam therapy A. Carlino1,2, H. Palmans1,3, G. Kragl1, E. Traneus4, C. Gouldstone3, S. Vatnitsky1, M. Stock1 1 EBG MedAustron GmbH, Medical Physics, Wiener Neustadt, Austria 2 University of Palermo, Department of Physics and Chemistry, Palermo, Italy 3 National Physical Laboratory, Radiation dosimetry, Teddington, United Kingdom 4 Raysearch laboratories AB, Particle therapy, Stockholm, Sweden Purpose or Objective At MedAustron (MA) a quasi-discrete scanning beam delivery with protons has been established. The clinical implementation of this technology requires comprehensive end-to-end testing to ensure an accurate patient treatment process. The purpose of such end-toend testing is to confirm that the entire logistic chain of the radiation treatment, starting from CT imaging, treatment planning, patient positioning, monitor calibration and beam delivery is operable and leads to the dose delivery within a pre-defined tolerance. We present
Results The measured absolute dose to water obtained with the Farmer chamber in all delivered plans was within 2% of the TPS calculated dose. A lateral 2D homogeneity of 3% inside the treatment field was measured with EBT films. Doses determined with the alanine pellets after correction for the quenching effect showed a mean deviation within 3% and a maximum deviation below 7% in the homogeneous and anthropomorphic phantoms. Conclusion The end-to-end test procedures developed at MedAustron showed that the entire chain of radiation treatment works efficiently and with accurate dosimetric results. Our experience shows that alanine pellets are suitable detectors for dosimetry audits and developed procedures can be used to support implementation of scanning beam delivery technology in clinical practice .
dosimetric end-to-end procedures for protons based on customized anthropomorphic phantoms and different dosimetric techniques. Material and Methods A homogeneous polystyrene phantom and two anthropomorphic phantoms (pelvis and head phantom) have been customized to allocate different detectors such as radiochromic films, ionization chambers and alanine pellets. During testing, the phantoms were moving through the workflow as real patients to simulate the entire clinical procedure. The CT scans were acquired with pre-defined scan protocols used at MA for cranial and pelvic treatments. All treatment planning steps were performed with RayStation v5.0.2 treatment planning system (TPS). A physical dose of 10 Gy was planned to clinically shaped target volumes in order to achieve uniformity better than 0.5% on the dose delivered to the alanine pellets. In the treatment room the plans were delivered to the phantoms loaded either with alanine pellets and radiochromic EBT3 films (figure 1) or two Farmer chambers. The alanine pellets (5.0 mm diameter and 2.3 mm thickness) and their read-out were provided by the National Physical Laboratory (NPL). One of the challenges of alanine for dosimetry in particle beams is the known response dependency (quenching) on the charge, the fluence and the energy of the particles constituting the mixed radiation field. Corrections for this were derived by a Monte Carlo dose calculation platform implemented in a non-clinical version of RayStation.
Conclusion The investigated beam model showed excellent agreement with measured data over a wide range of field sizes and measurement depths with improved agreement for small field sizes. These commissioning results are a solid basis for ongoing investigations focusing on more complex treatment types such as IMRT and VMAT and heterogeneous phantoms. PO-0806 Dosimetric end-to-end test procedures using alanine dosimetry in scanned proton beam therapy A. Carlino1,2, H. Palmans1,3, G. Kragl1, E. Traneus4, C. Gouldstone3, S. Vatnitsky1, M. Stock1 1 EBG MedAustron GmbH, Medical Physics, Wiener Neustadt, Austria 2 University of Palermo, Department of Physics and Chemistry, Palermo, Italy 3 National Physical Laboratory, Radiation dosimetry, Teddington, United Kingdom 4 Raysearch laboratories AB, Particle therapy, Stockholm, Sweden Purpose or Objective At MedAustron (MA) a quasi-discrete scanning beam delivery with protons has been established. The clinical implementation of this technology requires comprehensive end-to-end testing to ensure an accurate patient treatment process. The purpose of such end-toend testing is to confirm that the entire logistic chain of the radiation treatment, starting from CT imaging, treatment planning, patient positioning, monitor calibration and beam delivery is operable and leads to the dose delivery within a pre-defined tolerance. We present
Results The measured absolute dose to water obtained with the Farmer chamber in all delivered plans was within 2% of the TPS calculated dose. A lateral 2D homogeneity of 3% inside the treatment field was measured with EBT films. Doses determined with the alanine pellets after correction for the quenching effect showed a mean deviation within 3% and a maximum deviation below 7% in the homogeneous and anthropomorphic phantoms. Conclusion The end-to-end test procedures developed at MedAustron showed that the entire chain of radiation treatment works efficiently and with accurate dosimetric results. Our experience shows that alanine pellets are suitable detectors for dosimetry audits and developed procedures can be used to support implementation of scanning beam delivery technology in clinical practice .