Stefania Clemente1, Maria Daniela Falco2, Elisabetta Cagni3, Cinzia Talamonti4, Mafalda Boccia5, Eva Gino6, Elena Lorenzini7, Federica Rosica8, Serenella Russo9, Alessandro Alparone10, Daniele Zefiro11, Christian Fiandra12. 1. Unit of Medical Physics and Radioprotection, Federico II University Hospital, Napoli, Italy. 2. Department of Radiation Oncology, "G. D'Annunzio" University, "SS. Annunziata" Hospital, Chieti, Italy. 3. Medical Physics Unit, Azienda USL-IRCCS di Reggio Emilia, Reggio Emilia, Italy. 4. Medical Physics Unit, University Of Florence, Azienda Ospedaliero Universitaria Careggi, Florence, Italy. 5. Polydiagnostic Center Check - Up S.r.l, Salerno, Italy. 6. Medical PhysicDepartment, A.O. Ordine Mauriziano, Turin, Italy. 7. U.O.C Fisica Sanitaria Area Nord, Azienda USL Nord Ovest Toscana, Massa Carrara, Italy. 8. U.O.C. Fisica Sanitaria, ASL di Teramo, Italy. 9. Medical Physics Unit, AUSL Toscana Centro, Florence, Italy. 10. R&D Department, Tecnologie Avanzate, Turin, Italy. 11. MedicaPhysics Unit, ASL5 Sistema Sanitario Regione Liguria, La Spezia, Italy. 12. Department of Oncology, University of Turin, Turin, Italy.
Abstract
OBJECTIVES: This multicentric study was carried out to investigate the impact of small field output factors (OFs) inaccuracies on the calculated dose in volumetric arctherapy (VMAT) radiosurgery brain plans. METHODS: Nine centres, realised the same five VMAT plans with common planning rules and their specific clinical equipment Linac/treatment planning system commissioned with their OFs measured values (OFbaseline). In order to simulate OFs errors, two new OFs sets were generated for each centre by changing only the OFs values of the smallest field sizes (from 3.2 × 3.2 cm2 to 1 × 1 cm2) with well-defined amounts (positive and negative). Consequently, two virtual machines for each centre were recommissioned using the new OFs and the percentage dose differences ΔD (%) between the baseline plans and the same plans recalculated using the incremented (OFup) and decremented (OFdown) values were evaluated. The ΔD (%) were analysed in terms of planning target volume (PTV) coverage and organs at risk (OARs) sparing at selected dose/volume points. RESULTS: The plans recalculated with OFdown sets resulted in higher variation of doses than baseline within 1.6 and 3.4% to PTVs and OARs respectively; while the plans with OFup sets resulted in lower variation within 1.3% to both PTVs and OARs. Our analysis highlights that OFs variations affect calculated dose depending on the algorithm and on the delivery mode (field jaw/MLC-defined). The Monte Carlo (MC) algorithm resulted significantly more sensitive to OFs variations than all of the other algorithms. CONCLUSION: The aim of our study was to evaluate how small fields OFs inaccuracies can affect the dose calculation in VMAT brain radiosurgery treatments plans. It was observed that simulated OFs errors, return dosimetric calculation accuracies within the 3% between concurrent plans analysed in terms of percentage dose differences at selected dose/volume points of the PTV coverage and OARs sparing. ADVANCES IN KNOWLEDGE: First multicentre study involving different Planning/Linacs about undetectable errors in commissioning output factor for small fields.
OBJECTIVES: This multicentric study was carried out to investigate the impact of small field output factors (OFs) inaccuracies on the calculated dose in volumetric arctherapy (VMAT) radiosurgery brain plans. METHODS: Nine centres, realised the same five VMAT plans with common planning rules and their specific clinical equipment Linac/treatment planning system commissioned with their OFs measured values (OFbaseline). In order to simulate OFs errors, two new OFs sets were generated for each centre by changing only the OFs values of the smallest field sizes (from 3.2 × 3.2 cm2 to 1 × 1 cm2) with well-defined amounts (positive and negative). Consequently, two virtual machines for each centre were recommissioned using the new OFs and the percentage dose differences ΔD (%) between the baseline plans and the same plans recalculated using the incremented (OFup) and decremented (OFdown) values were evaluated. The ΔD (%) were analysed in terms of planning target volume (PTV) coverage and organs at risk (OARs) sparing at selected dose/volume points. RESULTS: The plans recalculated with OFdown sets resulted in higher variation of doses than baseline within 1.6 and 3.4% to PTVs and OARs respectively; while the plans with OFup sets resulted in lower variation within 1.3% to both PTVs and OARs. Our analysis highlights that OFs variations affect calculated dose depending on the algorithm and on the delivery mode (field jaw/MLC-defined). The Monte Carlo (MC) algorithm resulted significantly more sensitive to OFs variations than all of the other algorithms. CONCLUSION: The aim of our study was to evaluate how small fields OFs inaccuracies can affect the dose calculation in VMAT brain radiosurgery treatments plans. It was observed that simulated OFs errors, return dosimetric calculation accuracies within the 3% between concurrent plans analysed in terms of percentage dose differences at selected dose/volume points of the PTV coverage and OARs sparing. ADVANCES IN KNOWLEDGE: First multicentre study involving different Planning/Linacs about undetectable errors in commissioning output factor for small fields.
Authors: Serenella Russo; Giacomo Reggiori; Elisabetta Cagni; Stefania Clemente; Marco Esposito; Maria Daniela Falco; Christian Fiandra; Francesca Romana Giglioli; Marco Marinelli; Carmelo Marino; Laura Masi; Maria Pimpinella; Michele Stasi; Lidia Strigari; Cinzia Talamonti; Elena Villaggi; Pietro Mancosu Journal: Phys Med Date: 2016-11-08 Impact factor: 2.685
Authors: Ans C C Swinnen; Michel C Öllers; Erik Roijen; Sebastiaan M Nijsten; Frank Verhaegen Journal: J Appl Clin Med Phys Date: 2017-01-03 Impact factor: 2.102
Authors: Daniela Schmitt; Oliver Blanck; Tobias Gauer; Michael K Fix; Thomas B Brunner; Jens Fleckenstein; Britta Loutfi-Krauss; Peter Manser; Rene Werner; Maria-Lisa Wilhelm; Wolfgang W Baus; Christos Moustakis Journal: Strahlenther Onkol Date: 2020-03-24 Impact factor: 3.621