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Quality assurance of rapidarc treatments with FFF
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Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
tude pulmonary movements (>5 cm). For amplitudes of 5 cm, 10.2% of healthy lung tissue receiving 20 Gy was spared with IMRT and 9.7% with VMAT compared to non-gated treatments. The size of the tumor appeared to be an important selection criterion: the volume of healthy tissue spared increased with tumors volume. Conclusion: The commissioning of this new technique was satisfying. IMRT and VMAT gating should only be used clinically for large and mobile tumors to obtain the greatest dosimetric benefit and to counterbalance the decrease in patient comfort due to the longer treatment delivery time. http://dx.doi.org/10.1016/j.ejmp.2013.08.117
112 PRE-TREATMENT QUALITY ASSURANCE FOR STEREOTACTIC CRANIAL PLANS C. Sedmak, A. Dubouloz, G. Dipasquale, P. Nouet, M. Rouzaud. Radiation Oncology, Geneva University Hospitals, Switzerland Objective: To report the results of Quality Assurance (QA) dose planning for stereotactic cranial treatments delivered with Dynamic Conformal Arcs (DCA) or Volumetric Modulated Arc Therapy (VMAT) techniques. Material and methods: A total of 26 dose plans, 19 patients with DCA from IplanÒ (Brainlab) and 7 patients with VMAT from EclipseTM (Varian), were verified with different QA methods. Plans were delivered on a Novalis TX unit. Each treatment field was checked for absolute isocenter dose using a LucyÒ 3D QA Phantom (Standard Imaging) and a Diamond chamber (PTW). GafchromicTM EBT3 film dosimetry (ISP) was selected to verify total dose plans in the 2D axial planes. A flatbed RGB scanner (Epson Expression 10,000 XL) was used to digitize the films and the RIT software to analyze the data (gamma criteria 1 mm and 3%). Relative dose analysis was performed normalized at isocenter. Same criteria were used for Portal dosimetry (PD) verifications of VMAT plans. Finally for DCA plans, manual independent Monitor Units Calculation (MUC) number was implemented. Results: Absolute isocenter dose measurements: the mean dose ratio (measured/expected) was for DCA (total of 102 fields, dose range 0.3–6 Gy), and for VMAT treatments (a total of 22 treatment fields, and dose range 0.3–1.3 Gy) 1.014 (SD 0.017) and 1.034 (SD 0.031) respectively. Films: the mean gamma agreement index (GAI) was for DCA plans (3 patients) and VMAT plans (3 patients) 99.9% (SD 0.1%) and 93.0 (SD 3.9%) respectively. PD: for VMAT plans (22 fields) the mean GAI was 93.4% (SD 3.4%). MUC: the mean relative difference over 102 treatment fields was 0.02% (SD 1.64%). Conclusion: DCA QA results were excellent. VMAT, chosen to better spare organ at risk with its modulation, showed worst results likely for this last feature. HybridArc will next be tested. http://dx.doi.org/10.1016/j.ejmp.2013.08.118
113 QUALITY ASSURANCE OF RAPIDARC TREATMENTS WITH FFF J. Molinier, S. Siméon, N. Ailleres, L. Bedos, N. Aillères, P. Fenoglietto. Institut Régional du Cancer, Val-d’Aurelle, Montpellier, France Introduction: With a maximum dose rate of 1400 MU/min X6FFF (Flattening Filter Free) is a major device for the development of hypofractionated stereotactic treatments. But the use of such a dose rate requires specific quality controls. The purpose of this study is to evaluate the feasibility of these controls and the validation of X6FFF RapidArc treatment delivery.
Material and methods: First of all, simple fields (square, rectangular and MLC) were analyzed. Absolute dose measures at the isocenter were performed with a 0.125 cc ionization chamber and a cylindrical water equivalent phantom. Planar dose distribution at the isocenter was verified with portal imager (aS1000) and EpiQA software (Epidos, Brastislavia). In this case, the analysis was performed using GAI (3%–3 mm) and smoothing detector response to adjust the resolution to the TPS dose calculation (2.5 mm/pixel). Then, 20 patients (10 prostates, 5 livers and 5 lungs), previously treated in X6 RapidArc, were replanned in X6FFF with Eclipse TPS (PRO v10 and AAA v10). They were checked on TrueBeam Novalis linear accelerator using the same devices as for simple fields. Results: The variation of the correction factor for recombination between 1400 and 600 MU/min is less than 0.5%. For simple fields, GAI is 95.45%. The difference in absolute dose for 20 RapidArc plans is 1.7 ± 2.51% (mean ± 1 SD). This value is 1.23 ± 1.29% for prostate, 1.95 ± 2.59% for liver, 2.15 ± 3.74% for lung. As regards the comparison of dose distribution the overall GAI is 99.26 ± 0.75% (99.12 ± 0.76% for prostate, 99.27 ± 0.69% for liver et 99.46 ± 0.83% for lung). Conclusion: RapidArc treatment delivery in X6FFF is dosimetrically acceptable and comparable to those obtained in X6.
http://dx.doi.org/10.1016/j.ejmp.2013.08.119
POSTER SESSION: TREATMENT PLANNING AND ANALYSIS 114 FEASIBILITY STUDY OF TOTAL MARROW IRRADIATION USING HELICAL TOMOTHERAPY M. Chea 1, C. Llagostera 2, P. Meyer 3, K. Cristina 1, R. Itti 4, F. Culot 1, L. De Marzi 5, X. Cuenca 1, M.A. Mahé 2, J.J. Mazeron 1, A. Lisbona 2, C. Jenny 1. 1 Groupe Hospitalier Pitié-Salpétrière, Paris, France, 2 Institut Cancérologie de l’Ouest, Centre René Gauducheau, Nantes, France, 3 Centre Paul Strauss, Strasbourg, France, 4 Hôpital Saint Louis, Paris, France, 5 Institut Curie, Centre de Protonthérapie, Orsay, France Introduction: The clinical investigation project TOMMY suggests an alternative study to Total Body Irradiation (TBI): Total Marrow Irradiation (TMI) which reduces radiation doses to healthy tissues and allows dose escalation. We decided to study the feasibility of TMI using helical tomotherapy. Material and methods: The output drift over 40 min was evaluated. The treatment planning was performed on a patient’s CT with the following objective and constraints: D85 PTV = prescribed dose (12 Gy) and D50 OAR < 25%, 50% or 65% of the prescribed dose. We studied the impact of the parameters (Pitch, Modulation Factor and Field width) on the treatment planning. We checked the dose delivery by simulating a TMI on a CIRS thorax and on a CIRS pelvis phantom. The dose measurements were performed with an ion chamber (lung, spine and femoral head) and films. The same treatment plan was recalculated in a homogeneous media. As TMI has to be split in 2 segments that are joined at mid-thigh, two junction methods (‘‘Tomo-Linac” using extended SSD and ‘‘Full Tomo” using a controlled gradient dose) were evaluated on a Cheese Phantom. The in vivo dosimetry feasibility was studied with TLD on patients treated by TBI with Tomotherapy. Results: The estimated output drift is 1.7%. Treatment planning parameters were determined to have the optimum balance between PTV coverage and treatment time. The results of treatment planning are consistent with values found in literature. Measured and calculated doses are in good agreement in an inhomogeneous and in a homogenous media. Nevertheless we notice that the dose measured
Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
tude pulmonary movements (>5 cm). For amplitudes of 5 cm, 10.2% of healthy lung tissue receiving 20 Gy was spared with IMRT and 9.7% with VMAT compared to non-gated treatments. The size of the tumor appeared to be an important selection criterion: the volume of healthy tissue spared increased with tumors volume. Conclusion: The commissioning of this new technique was satisfying. IMRT and VMAT gating should only be used clinically for large and mobile tumors to obtain the greatest dosimetric benefit and to counterbalance the decrease in patient comfort due to the longer treatment delivery time. http://dx.doi.org/10.1016/j.ejmp.2013.08.117
112 PRE-TREATMENT QUALITY ASSURANCE FOR STEREOTACTIC CRANIAL PLANS C. Sedmak, A. Dubouloz, G. Dipasquale, P. Nouet, M. Rouzaud. Radiation Oncology, Geneva University Hospitals, Switzerland Objective: To report the results of Quality Assurance (QA) dose planning for stereotactic cranial treatments delivered with Dynamic Conformal Arcs (DCA) or Volumetric Modulated Arc Therapy (VMAT) techniques. Material and methods: A total of 26 dose plans, 19 patients with DCA from IplanÒ (Brainlab) and 7 patients with VMAT from EclipseTM (Varian), were verified with different QA methods. Plans were delivered on a Novalis TX unit. Each treatment field was checked for absolute isocenter dose using a LucyÒ 3D QA Phantom (Standard Imaging) and a Diamond chamber (PTW). GafchromicTM EBT3 film dosimetry (ISP) was selected to verify total dose plans in the 2D axial planes. A flatbed RGB scanner (Epson Expression 10,000 XL) was used to digitize the films and the RIT software to analyze the data (gamma criteria 1 mm and 3%). Relative dose analysis was performed normalized at isocenter. Same criteria were used for Portal dosimetry (PD) verifications of VMAT plans. Finally for DCA plans, manual independent Monitor Units Calculation (MUC) number was implemented. Results: Absolute isocenter dose measurements: the mean dose ratio (measured/expected) was for DCA (total of 102 fields, dose range 0.3–6 Gy), and for VMAT treatments (a total of 22 treatment fields, and dose range 0.3–1.3 Gy) 1.014 (SD 0.017) and 1.034 (SD 0.031) respectively. Films: the mean gamma agreement index (GAI) was for DCA plans (3 patients) and VMAT plans (3 patients) 99.9% (SD 0.1%) and 93.0 (SD 3.9%) respectively. PD: for VMAT plans (22 fields) the mean GAI was 93.4% (SD 3.4%). MUC: the mean relative difference over 102 treatment fields was 0.02% (SD 1.64%). Conclusion: DCA QA results were excellent. VMAT, chosen to better spare organ at risk with its modulation, showed worst results likely for this last feature. HybridArc will next be tested. http://dx.doi.org/10.1016/j.ejmp.2013.08.118
113 QUALITY ASSURANCE OF RAPIDARC TREATMENTS WITH FFF J. Molinier, S. Siméon, N. Ailleres, L. Bedos, N. Aillères, P. Fenoglietto. Institut Régional du Cancer, Val-d’Aurelle, Montpellier, France Introduction: With a maximum dose rate of 1400 MU/min X6FFF (Flattening Filter Free) is a major device for the development of hypofractionated stereotactic treatments. But the use of such a dose rate requires specific quality controls. The purpose of this study is to evaluate the feasibility of these controls and the validation of X6FFF RapidArc treatment delivery.
Material and methods: First of all, simple fields (square, rectangular and MLC) were analyzed. Absolute dose measures at the isocenter were performed with a 0.125 cc ionization chamber and a cylindrical water equivalent phantom. Planar dose distribution at the isocenter was verified with portal imager (aS1000) and EpiQA software (Epidos, Brastislavia). In this case, the analysis was performed using GAI (3%–3 mm) and smoothing detector response to adjust the resolution to the TPS dose calculation (2.5 mm/pixel). Then, 20 patients (10 prostates, 5 livers and 5 lungs), previously treated in X6 RapidArc, were replanned in X6FFF with Eclipse TPS (PRO v10 and AAA v10). They were checked on TrueBeam Novalis linear accelerator using the same devices as for simple fields. Results: The variation of the correction factor for recombination between 1400 and 600 MU/min is less than 0.5%. For simple fields, GAI is 95.45%. The difference in absolute dose for 20 RapidArc plans is 1.7 ± 2.51% (mean ± 1 SD). This value is 1.23 ± 1.29% for prostate, 1.95 ± 2.59% for liver, 2.15 ± 3.74% for lung. As regards the comparison of dose distribution the overall GAI is 99.26 ± 0.75% (99.12 ± 0.76% for prostate, 99.27 ± 0.69% for liver et 99.46 ± 0.83% for lung). Conclusion: RapidArc treatment delivery in X6FFF is dosimetrically acceptable and comparable to those obtained in X6.
http://dx.doi.org/10.1016/j.ejmp.2013.08.119
POSTER SESSION: TREATMENT PLANNING AND ANALYSIS 114 FEASIBILITY STUDY OF TOTAL MARROW IRRADIATION USING HELICAL TOMOTHERAPY M. Chea 1, C. Llagostera 2, P. Meyer 3, K. Cristina 1, R. Itti 4, F. Culot 1, L. De Marzi 5, X. Cuenca 1, M.A. Mahé 2, J.J. Mazeron 1, A. Lisbona 2, C. Jenny 1. 1 Groupe Hospitalier Pitié-Salpétrière, Paris, France, 2 Institut Cancérologie de l’Ouest, Centre René Gauducheau, Nantes, France, 3 Centre Paul Strauss, Strasbourg, France, 4 Hôpital Saint Louis, Paris, France, 5 Institut Curie, Centre de Protonthérapie, Orsay, France Introduction: The clinical investigation project TOMMY suggests an alternative study to Total Body Irradiation (TBI): Total Marrow Irradiation (TMI) which reduces radiation doses to healthy tissues and allows dose escalation. We decided to study the feasibility of TMI using helical tomotherapy. Material and methods: The output drift over 40 min was evaluated. The treatment planning was performed on a patient’s CT with the following objective and constraints: D85 PTV = prescribed dose (12 Gy) and D50 OAR < 25%, 50% or 65% of the prescribed dose. We studied the impact of the parameters (Pitch, Modulation Factor and Field width) on the treatment planning. We checked the dose delivery by simulating a TMI on a CIRS thorax and on a CIRS pelvis phantom. The dose measurements were performed with an ion chamber (lung, spine and femoral head) and films. The same treatment plan was recalculated in a homogeneous media. As TMI has to be split in 2 segments that are joined at mid-thigh, two junction methods (‘‘Tomo-Linac” using extended SSD and ‘‘Full Tomo” using a controlled gradient dose) were evaluated on a Cheese Phantom. The in vivo dosimetry feasibility was studied with TLD on patients treated by TBI with Tomotherapy. Results: The estimated output drift is 1.7%. Treatment planning parameters were determined to have the optimum balance between PTV coverage and treatment time. The results of treatment planning are consistent with values found in literature. Measured and calculated doses are in good agreement in an inhomogeneous and in a homogenous media. Nevertheless we notice that the dose measured