Scherrer Institute International Conference on Medical Accelerators and Particle Therapy 46 th September 2019 Page 2 Overview of presentation Proton therapy and its delivery Improving ID: 1030438
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1. Dose deliveryTony Lomax :: Head of Medical Physics :: Paul Scherrer InstituteInternational Conference on Medical Accelerators and Particle Therapy – 4-6th September 2019
2. Page 2Overview of presentationProton therapy and its deliveryImproving lateral penumbraReducing treatment timesProtons for FLASH?Summary
3. Page 3Overview of presentationProton therapy and its deliveryImproving lateral penumbraReducing treatment timesProtons for FLASH?Summary
4. Why protons for cancer therapy?targetDepthDose15MV photons177MeV protonsSOBP extentProton therapy and its delivery
5. Making protons useful (1): Passive scattering1st scatterer2nd scattererTargetDrift spaceRange shifter wheel (fixed SOBP extent across field)Proton therapy and its delivery
6. Irradiation of eye tumors> 7000 patients treated @ PSI> 20% of all patients treated with proton world-wideTumor control rate of 98%Passive scattering for ocular tumours – a success storyProton therapy and its delivery
7. TargetMagnetic scannerChange energyPatientProton pencil beamPedroni et al 1995, Med. Phys. 22:37-53.Making protons useful (2): Pencil beam scanningProton therapy and its delivery
8. Pencil beam scanning (PBS)Passive scatteringPassive scattering and Pencil beam scanning comparedProton therapy and its deliveryFixed SOBP extent
9. Ependymomas50 Patients5y Local control: 78%Skull base tumours222 Patients7y Local control: 80%Sacral chordomas36 Patients5y Local control: 66%The bottom line – Clinical results with PBS (PSI)Proton therapy and its delivery
10. By end of 2018, there are over 90 PBS treatment rooms around the worldThe success of PBSProton therapy and its delivery
11. Page 11Overview of presentationProton therapy and its deliveryImproving lateral penumbraReducing treatment timesProtons for FLASH?Summary
12. Lateral penumbras for proton therapy 80-20% penumbraPS - CollimatedPBS – Un-collimatedImproving penumbra
13. The conventional approach: Rectilinear scanning Meier et al 2017, Phys. Med. Biol. 62 2398-2416Contour scanningImproving penumbra
14. Meier et al 2017, Phys. Med. Biol. 62 2398-2416Contour scanningImproving penumbraA more logical approach: Contour based
15. Rectilinear (A)Contour (B)Difference (B-A)Brainstem dose reduced by ~10% with contour scanning Improving penumbraContour scanningMeier et al 2017, Phys. Med. Biol. 62 2398-2416
16. Collimation for PBS proton therapy?Improving penumbraPS - CollimatedPBS – Un-collimatedPBS – Collimated64202460.00.20.40.60.81.01.2CollimatorCollimatorCollimated PBSWinterhalter 2018, PMB 63(2):025022
17. Collimated contour scanning Meier et al 2017, Phys. Med. Biol. 62 2398-241664202460.00.20.40.60.81.01.2Profile (cm)Relative doseCollimatorCollimatorImproving penumbraCollimation for PBS proton therapy?
18. Uncollimated PBS (A)Contour + collimation (B)Difference (B-A)Winterhalter 2018, PMB 64(1):015002Brainstem dose reduced by ~20% Collimated (energy specific) contour scanningImproving penumbra
19. Page 19Overview of presentationProton therapy and its deliveryImproving lateral penumbraReducing treatment timesProtons for FLASH?Summary
20. David Meer and Grischa Klimpki, PSIE.g. Line/continuous scanningSpot (discrete) scanningReducing delivery times
21. E.g. Line/continuous scanningDavid Meer and Grischa Klimpki, PSISpot (discrete) scanningLine (continuous) scanningc.f. ‘Step-and-shoot’c.f. ‘Sliding-window’Reducing delivery times
22. ExpectedDiscreteContinuousLine/continuous scanningReducing delivery timesTreatment times for 0.6Gy delivered to a 300ml target volumeSpot scanning – 23sLine scanning – 10s David Meer and Grischa Klimpki, PSI
23. Bragg peaks (spots) for field 14 field IMPT plan~8250 spots per fieldSpot reductionDo we need so many ‘spots’?Reducing delivery times
24. Conventional PBSSpot reducedSpot reduction optimisationReducing delivery timesSpot reductionLomax et al, ESTRO 2003, Geneva van de Water et al. Physics in Medicine & Biology 2013, 58Belosi et al, PTCOG57, Cincinnati, 2018
25. Lomax et al, ESTRO 2003, Geneva van de Water et al. Physics in Medicine & Biology 2013, 58Belosi et al, PTCOG57, Cincinnati, 2018~8250 spots per field~380 spots per fieldConventional PBSSpot reducedSpot reduction optimisationReducing delivery timesSpot reduction
26. Belosi et al, PTCOG57, Cincinnati, 2018Conventional planSpots/field~8250Delivery time/field (s)~50 ConventionalDoes this reduce treatment time?6Gy/sReducing delivery times
27. Belosi et al, PTCOG57, Cincinnati, 2018Conventional planSpot reduced planSpots/field~8250~380Delivery time/field (s)~50 ~28 Spot reductionConventionalSpot reduced6Gy/s6Gy/sReducing delivery timesDoes this reduce treatment time?
28. Page 28Overview of presentationProton therapy and its deliveryImproving lateral penumbraReducing treatment timesProtons for FLASH?Summary
29. Page 29Montay-Gruel et al Radiother Oncol 2017;124:365–369Protons for FLASH?The FLASH effect – Whole brain irradiation of miceIrradiation: 10Gy @ 0.1 – 5MGy/s (4.5 MeV electrons)Endpoints: Memory preservation (Recognition ratio)… result in ~20% increase in memory preservation…Dose rates > 30Gy/s…
30. Protons for FLASH?Protons for FLASH?Proton dose rates6Gy/s60Gy/s3300Gy/s!Limited by monitoring and regulatory issues!Beam intensities without monitoring/ regulatory limitations Energy specific beam intensities at PSI
31. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughPBS proton therapy for FLASH – How can we best exploit these intensities?
32. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughPBS proton therapy for FLASH – How can we best exploit these intensities?
33. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughPBS proton therapy for FLASH – How can we best exploit these intensities?
34. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughPBS proton therapy for FLASH – How can we best exploit these intensities?
35. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughDose distributionsDose rate distributionsEstimated dose rates for 6Gy fraction
36. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughDose distributionsDose rate distributionsEstimated dose rates for 6Gy fraction
37. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughDose distributionsDose rate distributionsEstimated dose rates for 6Gy fraction
38. 2040608095107[%]Range compensated/ spot reductionProtons for FLASH?Van de Water 2019, Acta OncolgicaSingle energy (230MeV)ClinicalSpot-reducedShoot throughDose distributionsDose rate distributionsEstimated dose rates for 6Gy fraction
39. SummaryThe 3D localization of the Bragg peak allows for high degrees of modulation, leading to exquisite levels of dose conformationPBS is currently the most flexible and (now) most widely used delivery modalityBut improvements are still necessary…Reducing treatment timesImproving lateral penumbraFLASH compatible PBS…Whatever, there are still lots of interesting developments to be done in accelerators, beam delivery, medical physics, biology and clinics…
40. Thanks for your attention.