A model for assessing VMAT pre-treatment verification systems and VMAT optimization algorithms

Transcription

1 1 st Workshop: Radiotherapy Modelling - Luz Saint Sauveur, Sep 2016 A model for assessing VMAT pre-treatment verification systems and VMAT optimization algorithms A R Barbeiro 1, A Ureba 2, J A Baeza 3, R Linares 4, M Perucha 4, E Jiménez- Ortega 1 and A Leal 1 1. Dept. Fisiología Médica y Biofísica, University of Seville 2. Medical Radiation Physics, Stockholm University, Karolinska Institutet 3. Maastro Clinic, Maastricht, The Netherlands 4. Servicio de Radiofisica, Hospital Infanta Luisa, Seville

2 2 1 st Workshop SFPM: Radiotherapy Modelling Outline Introduction VMAT and QA systems, main issues and uncertainties, rationale for a highly accurate model. Purpose Material and Methods Linac modelling, MC simulation and verification, QuAArC phantom and QuAArC model. Results and Discussion QuAArC implementation with clinical cases, discretization effect and proof of concept study. Conclusions and future work

3 3 1 st Workshop SFPM: Radiotherapy Modelling Introduction Complexity of IMRT techniques is increasing. VMAT dynamic implementation: - Dynamic MLC motion - Dose rate - Gantry rotation speed Varying Simultaneously during irradiation demanding dose distributions; shorter treatment times & fewer MUs. New uncertainties, associated issues Webb & McQuaid PMB(54),2009 Rigorous QA correct delivery and consistency with the planning.

4 4 1 st Workshop SFPM: Radiotherapy Modelling Introduction 2D/3D QA systems COMPASS/MatriXX,IBA Film & Ion chamber MatriXX, IBA Chandraraj et al., J Appl Clin Med Phys(12) 2011 Boggula et al., PMB(56) 2011 Octavius, PTW Delta4, Scandidos ArckChek, Sun Nuclear PTW and Scandidos websites Hammond L. et al, Clinical Oncology(23) 2011

5 5 1 st Workshop SFPM: Radiotherapy Modelling Introduction Dose calculation accuracy in these conditions. Continuous delivery of a discrete calculation. Added complexity for optimization algorithms: - more variables; - connectivity (more or less robust solutions); Connectivity? Plan degeneration!! 6MeV degradado Y (cm) X (cm) DAO (Direct Aperture Optimization) (RapidArc ; SmartArc) FMO (Segmentation) + arc sequencing

6 6 1 st Workshop SFPM: Radiotherapy Modelling Monte Carlo simulation rationale Dose calculation accuracy: Explicit particle transport throughout the detailed geometry of linac and patient models. Scattered and transmitted radiation through the beam modifiers contribution of complex apertures.

7 7 1 st Workshop SFPM: Radiotherapy Modelling Introduction Continuous delivery of a discrete calculation: Machine Log files Information recorded during irradiation: MLC leaf and/or jaws positions; gantry angles; MU; etc. Dose reconstruction on the patient anatomy (discretization level TPS). (e.g. MobiusFX; MC simulation of DynaLog files for RapidArc QA with DOSXYZnrc dynamic source, Teke et al.) As a patient-specific QA method is controversial experimental dose measurements. High calculation resolution High detection density

8 8 1 st Workshop SFPM: Radiotherapy Modelling Purpose Log files information Full MC calculation. Absolute and 3D relative dose measurements. Entrance dose or fluence estimation. High spatial resolution Highly accurate model based on Monte Carlo simulation of log files, and on 3D radiochromic film measurements in a specific cylindrical phantom. specific cylindrical phantom QuAArC model

9 9 1 st Workshop SFPM: Radiotherapy Modelling Materials and Methods EGSnrc/BEAMnrc: geometry modelling and 6MV beams simulation MLC Tilt effect Leaf lateral view

10 % Dose 10 1 st Workshop SFPM: Radiotherapy Modelling EGSnrc/DOSXYZnrc: dose distributions calculation in a water phantom PDDs & OARs: MC vs. Measurements Agreement ±2%

11 11 1 st Workshop SFPM: Radiotherapy Modelling Materials and Methods MLC models (leakadge, gap and tilt study): additional experimental measurements with radiochromic film. MC showed high agreement with film

12 12 1 st Workshop SFPM: Radiotherapy Modelling Automatic MC verification of TPS (RTP files) and log files Materials and Methods TPS MOSAIQ LINAC BEAMnrc MC simulation BEAMDOSE

13 13 1 st Workshop SFPM: Radiotherapy Modelling Automatic MC verification of TPS (RTP files) and log files Materials and Methods TPS MOSAIQ LINAC BEAMnrc MC simulation Log file BEAMDOSE

14 14 1 st Workshop SFPM: Radiotherapy Modelling MC simulation of Log files Different discretization level effect in the verification process.

15 15 1 st Workshop SFPM: Radiotherapy Modelling MC simulation of Log files Different discretization level effect in the verification process.

16 16 1 st Workshop SFPM: Radiotherapy Modelling MC simulation of Log files Different discretization level effect in the verification process.

17 difference (cm) 17 1 st Workshop SFPM: Radiotherapy Modelling MC simulation of log files Log file analysis MLC leaf positions difference between RTP and LOG Mu distribution for the entire arc 6 RTP MU LOG MU

18 18 1 st Workshop SFPM: Radiotherapy Modelling Materials and Methods QuAArC phantom: Big setup: 30 cm x 30 cm length Small setup: 20 cm x 28 cm length Inner film scroll: dose distribution Outer film scroll: entrance dose estimation 3D relative dose measurements & absolute point dose measurements

19 19 1 st Workshop SFPM: Radiotherapy Modelling Dose processing and 3D dose reconstruction: Materials and Methods Feedback process to experimentally adjust MUs with measurements A x b 1 min x 2 C x d 2 such that Aeq x = beq 2 lb x ub

20 20 1 st Workshop SFPM: Radiotherapy Modelling Materials and Methods Feedback process proposed MU variations for IMRT and VMAT plans. IMRT plan VMAT plan

21 21 1 st Workshop SFPM: Radiotherapy Modelling QuAArC model validation with clinical cases: Materials and Methods Clinical cases planned with different conventional TPS: - MONACO - PINNACLE Verified with different commercial systems: - Delta4 - COMPASS Some of them were not accepted during their verification (2 treatment plans for a same case).

22 22 1 st Workshop SFPM: Radiotherapy Modelling Results Final QuAArC phantom - experimental verification: Rolled up radiochromic EBT3 films PMMA slices for axial films With cork cylinders

23 Inner Film 0-360º Outer Film º Outer Film 0-180º 23 1 st Workshop SFPM: Radiotherapy Modelling Results Reproducibility of film scroll measuments in QuAArC. Film Dose Distributions % Dose Difference γ (3%/3mm) High reproducibility: γ < 1: > 99%

24 Axial slice (mm) 24 1 st Workshop SFPM: Radiotherapy Modelling Results QuAArC model implementation Discretization level effect in treatment verification: % Dose Differences coarse discretization Film vs MC Log Film vs QuAArC solution % Dose Differences fine discretization Film vs MC Log Film vs QuAArC solution Gantry angle ( )

25 25 1 st Workshop SFPM: Radiotherapy Modelling Results QuAArC model implementation: coarse Vs. fine log (a) (b) (c) (d) (e) (f)

26 Axial slice (mm) Axial slice (mm) 26 1 st Workshop SFPM: Radiotherapy Modelling Proof of concept of the feedback process Results Film Dose Distributions A x b 1 min x 2 C x d 2 such that Aeq x = beq 2 lb x ub QuAArC Dose Distributions PINNACLE/COMPASS Plans % Dose Differences Gamma Analysis (2%/2mm) Prostate case Prostate VMAT Plan Outer scroll Inner scroll Gantry angle ( ) H&N case Film Dose Distributions QuAArC Dose Distributions H&N VMAT Plan % Dose Differences Gamma Analysis (2%/2mm) Outer scroll Inner scroll Gantry angle ( )

27 27 1 st Workshop SFPM: Radiotherapy Modelling Results DVHs PINNACLE TPS Vs. QuAArC PINNACLE/COMPASS Plans

28 28 1 st Workshop SFPM: Radiotherapy Modelling Results DVHs COMPASS Vs. QuAArC PINNACLE/COMPASS Plans

29 Axial slice (mm) 29 1 st Workshop SFPM: Radiotherapy Modelling Proof of concept of the feedback process Results Prostate case Film Dose Distributions A x b 1 min x 2 C x d 2 such that Aeq x = beq 2 lb x ub QuAArC Dose Distributions Plan A % Dose Differences MONACO/Delta4 Plans Gamma Analysis (2%/2mm) Plan B Outer scroll Inner scroll Outer scroll Inner scroll Gantry angle ( )

30 Axial slice (mm) 30 1 st Workshop SFPM: Radiotherapy Modelling Proof of concept of the feedback process Results H&N case Film Dose Distributions A x b 1 min x 2 C x d 2 such that Aeq x = beq 2 lb x ub QuAArC Dose Distributions Plan A MONACO/Delta4 Plans % Dose Differences Gamma Analysis (2%/2mm) Plan B Outer scroll Inner scroll Outer scroll Inner scroll Gantry angle ( )

31 31 1 st Workshop SFPM: Radiotherapy Modelling DVHs for QuAArC model Vs. MONACO TPS Results (a) (b) (c) (d)

32 32 1 st Workshop SFPM: Radiotherapy Modelling Delta4-Anatomy (PB) Vs. QuAArC solutions Results

33 33 1 st Workshop SFPM: Radiotherapy Modelling Conclusions and future work QuAArC model showed to be consistent and robust. Effect of dose calculation accuracy and degree of detection density was assessed in the developed model. (more reliable solutions, DVHs) Potentially, control and reduce VMAT uncertainties, allowing evaluation of commercial VMAT systems and/or the optimization algorithm implemented in TPS. Further studies about VMAT efficiency against more established techniques in specific cases. QuAArC model for dose painting verification. QuAArC is being adapted for 4D verification. QuAArC can also be implemented without MC.

34 34 1 st Workshop SFPM: Radiotherapy Modelling Acknowledgments Funding: Spanish Ministry of Science and Technology and FEDER. Radiophysics department, Virgen Macarena Hospital, Seville. Radiophysics department, Virgen del Rocio Hospital, Seville. Radiophysics department, Infanta Luisa Clinic, Seville. Thank you for your attention!