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A new robust statistical method for treatment planning systems validation using experimental designs
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Abstracts / Physica Medica 32 (2016) 196–221
A NEW ROBUST STATISTICAL METHOD FOR TREATMENT PLANNING SYSTEMS VALIDATION USING EXPERIMENTAL DESIGNS S. Dufreneix a,*, K. Briand b, C. Di Bartolo a, C. Legrand a, M. Bremaud a, J. Mesgouez a, T. Tiplica b, D. Autret a a b ⇑
Department of Medical Physics, ICO – Paul Papin, Angers, France ISTIA, Angers University, Angers, France Corresponding author.
Introduction. Dose computation verification is an important part of acceptance testing. The IAEA Tecdoc 1540 and 1583 suggest comparing computed dose to measurements for several beam configurations. However, this process is time-consuming and results out of tolerance are often left unexplained. Purpose. To validate a treatment planning system using experimental designs which allow evaluating several parameters in a few tests selected by a robust statistical method. Materials and methods. The Taguchi table L36 (211 312) was used to determine the 72 beams needed to test the 7 parameters chosen: energy, MLC, depth, jaw field size in X, Y1 and Y2 directions and wedge. Measurements were conducted in water using a CC04 (IBA) on a TrueBeam STx, a TrueBeam Tx, a Trilogy and a C-serie clinac (Varian). Dose was computed using the AAA algorithm (Eclipse, version 11). The same raw data was used for all accelerators during the algorithm configuration. Results. The mean difference between computed and measured doses was 0.1 0.5% for all tested beams and all linacs with a maximum difference of 2.4% (under the 3% tolerance level). For all beams, the measured doses were within 0.6% for all linacs. No studied parameter led to statistically significant deviation between computed and measured doses. Conclusion. Experimental design is a robust statistical method to validate an algorithm. Only 2 h of measurements were needed to evaluate 7 parameters. Furthermore, the commissioned accelerators were found dosimetrically equivalent even though the linac characteristics differ. Disclosure. No disclosure. http://dx.doi.org/10.1016/j.ejmp.2016.07.684
CARBON AND OXIGEN MINIBEAM RADIATION THERAPY: A MONTE CARLO DOSIMETRY STUDY W. González *, C. Peucelle, Y. Prezado IMNC-UMR 8165, CNRS, Paris 11 Universities, 91406 Orsay Cedex, France ⇑ Corresponding author. Introduction. Minibeam radiation therapy (MBRT) is a promising RT approach born at synchrotrons that combines the use of a spatial fractionation of the dose with the utilization of submillimetric field sizes (500–700 lm). Contrary to conventional RT, the dose profiles in MBRT consist in peaks and valleys, making the peak-to-valleydose ratio a very important dosimetric parameter, since in order to spare the normal tissues, high PVDR and low valley doses are required. MBRT has been shown to further increase the normal tissue resistance compared to standard RT. Purpose. The aim of this work was to perform an in depth dosimetric evaluation of carbon and oxygen minibeam radiation therapy. Materials and methods. The dose distributions of rectangular minibeams of 600 lm 2 cm of C and O ions impinged in a water
phantom with the Monte Carlo simulation code GATE v6.2 (Geant4.9.5). Results. PVDR and valley doses were assessed for different irradiation configurations. In particular, a detailed evaluation of the role of secondary particle contamination of the valley doses, which is one of the more critical aspects of MBRT, has been carried out. Conclusion. The favourable dose distributions obtained indicate that these novel RT approaches might allow reducing the side effects in normal tissues. It should also make charged particle therapy more amenable to administration in either a single dose fraction. http://dx.doi.org/10.1016/j.ejmp.2016.07.685
COMPARATIVE PATIENT ORGAN DOSE LEVELS FOR MAXILLOFACIAL EXAMINATIONS PERFORMED WITH DIFFERENT RADIOLOGICAL FACILITIES Marta Sans-Merce a,b,*, Jérôme Damet a,c, Minerva Becker b a
Institute of Radiation Physics, Lausanne University Hospital, Switzerland b Department of Medical Imaging and Information Sciences, University Hospitals of Geneva, Switzerland c Department of Radiology, University of Otago, Christchurch, New Zealand ⇑ Corrresponding author. Introduction. Maxillofacial radiologic examinations often result in irradiation of the thyroid gland, parotid glands and lens due to primary exposure or scatter radiation. Organ exposure depends on imaging modalities and protocols. Purpose. The purpose of this investigation was to evaluate radiation doses to the above-mentioned organs for CT, cone beam CT (CBCT) and panoramic radiographs (orthopantomography, OPT). Materials and methods. The absorbed dose was measured on the surface of a head phantom with thermoluminescence dosimeters. The phantom was imaged with CT, CBCT and OPT using standardized protocols employed in clinical routine. The areas examined included the paranasal sinuses, the entire head and the mandible depending on the protocol used. Dose measurements were performed individually for each modality and each protocol. Results. Doses to the thyroid gland when located outside the area of interest were lowest for all modalities (range: 0.01–1.22 mGy; measurement uncertainty: 10% at k = 2). Depending on the examination protocol, doses to the eye lens (due to primary beam or scattered radiation) showed wide variability (range: 0.02–26.22 mGy). The parotid glands were the only organs systematically placed in the primary beam for all modalities and protocols. Values ranged from 1.40–29.11 mGy with the highest values for CT examinations. For OPT, doses to the parotid glands were strongly inhomogeneous due to its operating mode. Conclusion. CT was the most irradiating modality. The mean doses to the parotid glands were similar for CBCT and OPT, while doses to organs in the scattered field were systematically higher for CBCT than OPT. Disclosure. The authors declare that they have no relevant material or financial interests that relate to the research described in this study. http://dx.doi.org/10.1016/j.ejmp.2016.07.686
Abstracts / Physica Medica 32 (2016) 196–221
A NEW ROBUST STATISTICAL METHOD FOR TREATMENT PLANNING SYSTEMS VALIDATION USING EXPERIMENTAL DESIGNS S. Dufreneix a,*, K. Briand b, C. Di Bartolo a, C. Legrand a, M. Bremaud a, J. Mesgouez a, T. Tiplica b, D. Autret a a b ⇑
Department of Medical Physics, ICO – Paul Papin, Angers, France ISTIA, Angers University, Angers, France Corresponding author.
Introduction. Dose computation verification is an important part of acceptance testing. The IAEA Tecdoc 1540 and 1583 suggest comparing computed dose to measurements for several beam configurations. However, this process is time-consuming and results out of tolerance are often left unexplained. Purpose. To validate a treatment planning system using experimental designs which allow evaluating several parameters in a few tests selected by a robust statistical method. Materials and methods. The Taguchi table L36 (211 312) was used to determine the 72 beams needed to test the 7 parameters chosen: energy, MLC, depth, jaw field size in X, Y1 and Y2 directions and wedge. Measurements were conducted in water using a CC04 (IBA) on a TrueBeam STx, a TrueBeam Tx, a Trilogy and a C-serie clinac (Varian). Dose was computed using the AAA algorithm (Eclipse, version 11). The same raw data was used for all accelerators during the algorithm configuration. Results. The mean difference between computed and measured doses was 0.1 0.5% for all tested beams and all linacs with a maximum difference of 2.4% (under the 3% tolerance level). For all beams, the measured doses were within 0.6% for all linacs. No studied parameter led to statistically significant deviation between computed and measured doses. Conclusion. Experimental design is a robust statistical method to validate an algorithm. Only 2 h of measurements were needed to evaluate 7 parameters. Furthermore, the commissioned accelerators were found dosimetrically equivalent even though the linac characteristics differ. Disclosure. No disclosure. http://dx.doi.org/10.1016/j.ejmp.2016.07.684
CARBON AND OXIGEN MINIBEAM RADIATION THERAPY: A MONTE CARLO DOSIMETRY STUDY W. González *, C. Peucelle, Y. Prezado IMNC-UMR 8165, CNRS, Paris 11 Universities, 91406 Orsay Cedex, France ⇑ Corresponding author. Introduction. Minibeam radiation therapy (MBRT) is a promising RT approach born at synchrotrons that combines the use of a spatial fractionation of the dose with the utilization of submillimetric field sizes (500–700 lm). Contrary to conventional RT, the dose profiles in MBRT consist in peaks and valleys, making the peak-to-valleydose ratio a very important dosimetric parameter, since in order to spare the normal tissues, high PVDR and low valley doses are required. MBRT has been shown to further increase the normal tissue resistance compared to standard RT. Purpose. The aim of this work was to perform an in depth dosimetric evaluation of carbon and oxygen minibeam radiation therapy. Materials and methods. The dose distributions of rectangular minibeams of 600 lm 2 cm of C and O ions impinged in a water
phantom with the Monte Carlo simulation code GATE v6.2 (Geant4.9.5). Results. PVDR and valley doses were assessed for different irradiation configurations. In particular, a detailed evaluation of the role of secondary particle contamination of the valley doses, which is one of the more critical aspects of MBRT, has been carried out. Conclusion. The favourable dose distributions obtained indicate that these novel RT approaches might allow reducing the side effects in normal tissues. It should also make charged particle therapy more amenable to administration in either a single dose fraction. http://dx.doi.org/10.1016/j.ejmp.2016.07.685
COMPARATIVE PATIENT ORGAN DOSE LEVELS FOR MAXILLOFACIAL EXAMINATIONS PERFORMED WITH DIFFERENT RADIOLOGICAL FACILITIES Marta Sans-Merce a,b,*, Jérôme Damet a,c, Minerva Becker b a
Institute of Radiation Physics, Lausanne University Hospital, Switzerland b Department of Medical Imaging and Information Sciences, University Hospitals of Geneva, Switzerland c Department of Radiology, University of Otago, Christchurch, New Zealand ⇑ Corrresponding author. Introduction. Maxillofacial radiologic examinations often result in irradiation of the thyroid gland, parotid glands and lens due to primary exposure or scatter radiation. Organ exposure depends on imaging modalities and protocols. Purpose. The purpose of this investigation was to evaluate radiation doses to the above-mentioned organs for CT, cone beam CT (CBCT) and panoramic radiographs (orthopantomography, OPT). Materials and methods. The absorbed dose was measured on the surface of a head phantom with thermoluminescence dosimeters. The phantom was imaged with CT, CBCT and OPT using standardized protocols employed in clinical routine. The areas examined included the paranasal sinuses, the entire head and the mandible depending on the protocol used. Dose measurements were performed individually for each modality and each protocol. Results. Doses to the thyroid gland when located outside the area of interest were lowest for all modalities (range: 0.01–1.22 mGy; measurement uncertainty: 10% at k = 2). Depending on the examination protocol, doses to the eye lens (due to primary beam or scattered radiation) showed wide variability (range: 0.02–26.22 mGy). The parotid glands were the only organs systematically placed in the primary beam for all modalities and protocols. Values ranged from 1.40–29.11 mGy with the highest values for CT examinations. For OPT, doses to the parotid glands were strongly inhomogeneous due to its operating mode. Conclusion. CT was the most irradiating modality. The mean doses to the parotid glands were similar for CBCT and OPT, while doses to organs in the scattered field were systematically higher for CBCT than OPT. Disclosure. The authors declare that they have no relevant material or financial interests that relate to the research described in this study. http://dx.doi.org/10.1016/j.ejmp.2016.07.686