Accelerators and advanced beam technologies for a national center for particle beam radiation - PowerPoint Presentation

1. Accelerators and advanced beam technologies for a national center for particle beam radiation therapy researchDr. C. JohnstoneParticle Accelerator Corporation/MSU4/29/ 2014

2. AbstractAbout half of all cancer patients receive definitive radiation therapy and approximately two-thirds will receive radiation therapy at some point during their illness. Protons and light ions offer more conformal dose deposition than photons and a promise of gross reduction in late effects, higher cure rates, a more efficient treatment course and improved overall quality of life. Despite recognition of reported advantages, there is almost no research activity in the U.S. due to the lack of clinical accelerator facilities offering a combination of light ions for radiation therapy. Outside the U.S., there are only a few established proton-ion facilities and are not sufficient to perform the requisite radiobiological investigations and advanced clinical protocols and trials necessary as discussed in a recent NCI/DOE report [1].

3. Hadrons vs. Conventional Radiotherapy (Photons)Hadron therapy material from Silva Verdu-Andres / TERA foundation

4. Why NOT protonsWHY? – Widespread use of proton therapy limited by accelerator and beam delivery technology: size, and expense: large no. of treatment fractionsWhy would anyone choose x-rays over particle therapy?2/3 of cancer patients treated with radiation therapy: >95% with X-rays Radiation Dose Tissue TumorProtonCarbon

5. Why heavier ions vs protons

6. 1) C-ion RT is successful in the not treatable by other meansAdvanced Head & Neck cancers (non-SCC) Large skull base cancers Post-op recurrent rectal cancer Inoperable sarcomaRe-irradiation after photon radiotherapyLung cancer ( Single irradiation)Liver cancer ( Single & Two fractions) Pancreatic cancer (8~12 fractions)High risk prostate cancer (12~16 fractions) 2) Promising results are obtained in C-ion hypo- fractionated RT16 fractions in 4 weeksCurrent Status and Future Prospects for Carbon Ion Therapy at NIRS-HIMAC, Tadashi Kamada, MD, National Institute of Radiological Sciences, Research Center for Charged Particle Therapy, Chiba, Japan, CAARI conference, 2012

7. Accelerators for hadron therapySize MattersPhotons vs ProtonsThe reality – ultra compact proton facilities: “Specialty” accelerators: Mevion single-room proton therapy gantry-mounted cyclotron (top): no PBS ProTom ultra-compact synchrotron (bottom): low current, only PBSCarbon therapy: prohibitive cost and sizeNo PBSIsocenter opticsshownDWA sizemisleadingProTomMevionNo PBS! ! !

8. Effective Dose as a function of RateThe case for high dose: hypofractionation and radiobiologyEffective dose 50 (effect seen in 50% of population) as a function of dose rate, for various experimental tissues with both high and low / ratios A. van der Kogel. The dose rate effect In: M. Joiner, A. van der Kogel (eds), Basic Clinical Radiobiology, 4th edition. Hodder Education, London, p. 161, 2009.

9. Multi-ion capabilityp, He, Li, B, CO and Ne also desirableFast switching between ion species (1 sec)Energy range60 MeV/nucleon to 430 MeV/nucleonDepths up to 30 cm for carbon ionsField sizeAt least 20 x 20 cm2optimally up to 40 x 40 cm2Real-time imaging (radiography & CT: For tumor position verification and motion managementFor patient sizes up to 60 cm in depth. Dose delivery rates: Hypofractionation treatments in under one minute (ideally in one breath hold)7 Gy/8 sec for a cubic liter(corresponding to 4x1012 p/sec)Pencil beam scanning:Fast treatment for a large variety of tumor sizes and shapes. Two extremes are considered: 30 cm x 30 cm tumor single layer in depth and a cubic volumeTransverse scanning rate of 1-10 cm/msecEnergy step time of 10-100 msec(These are present state-of-the-art)Transverse beam size:selectable, with stable, Gaussian profiles.3 mm to 10 mm FWHMEnergy step sizeProtons: 2 MeV (~0.25 cm in range)Carbon: 2 MeV/nucleon (~0.1 cm in range)Lateral targeting accuracy at the Bragg peakProtons: ±0.5 mmCarbon: ±0.2 mmDose accuracy/fraction 2.5%monitored at ≥40 kHz during dose depositionRequirements

10. Translating Accelerator PerformanceDose Delivery Rate30 x 30 cm2 field single layer/energysweep step size 5 mm10 x 10 x 10 cm3 field 40 layers/energy stepssweep step size 5 mmNormal Fraction: 1-2 Gy/fraction1 Gy/min1 Gy/sec 1/60 x 1012 p/sec1 x 1012 p/sec 4/60 x 1012 p/sec4 x 1012 p/sec*(requires transverse scanning rate of 13 cm/sec and energy modulation time of 10 ms)Hypofraction Regime: 5-8 Gy/fraction5-8 Gy/min5-8 Gy/sec5-8 Gy/breathhold (5-8)/60 x 1012 p/sec5-8 x 1012 p/sec1 x 1012 p/sec (5-8)/60 x 1012 p/sec2-3 x 1013 p/sec*4 x 1012 p/sec**requires transverse scanning rate of 13 cm/sec and energy modulation time of 10 msRadiobiology: up to 20 Gy/fraction20 Gy/min20 Gy/sec20 Gy/breathhold (2)/60 x 1013 p/sec2 x 1013 p/sec2-4 x 1012 p/sec 8/60 x 1013 p/sec8 x 1013 p/sec*1-2 x 1013 p/sec**requires transverse scanning rate of 13 cm/sec and energy modulation time of 10 ms G. Coutrakon, et. al., Proceedings 1999 PAC

11. Synchrotrons – General AdvantagesStrengths …..Multi-specie ion beams, varying charge to mass ratioSophisticated Beam ControlSlow and Rapid Cycling versionsRespiration gatingSpace charge mitigationIntensity, amplitude smoothing beam deliveryVariable energy, discrete steps, no degraderPotential of Variable energy in single cycle

12. Example: Heavy Ion Medical Accelerator, Chiba, JapanHigh LET (100 keV/m) ions: He, C, Ni, Si, ArVarying charge to mass ratio: 1/2 - 1/7Range: 30 cm in soft tissue (800 MeV/n for Si)Dose Rate; 5 Gy/min over 22 cm 40 m diameter ringSophisticated beam controlsSpace charge mitigationExtraction (RFKO) Respiration gatingBeam Intensity and energy modulation

13. Slow cycling synchrotrons

14. A Solution: Rapid cycling synchrotronAdvantage of a Rapid Cycling Synchrotron (RCS) Beam spill remains the same, ~50% of cycle time, but the charge or dose delivered scales with the repetition rate for the SAME size ring. Smaller ring must have increased repetition rates for the same dose delivery time. Proposed cycle times are 15 Hz and 30 Hz

15. Best cyclotrons synchrotron

16. RCS – MORE commentsPulse to pulse energy variation and stability more difficultLess time to verify energySweeping longitudinally requires broad-band RF (low accelerating voltage, lossy), largeUltra-short timescale for magnetic component retuning – energy slew in one direction to avoid hysteresis effects. Ramp beam delivery system. These are very complex field ramps requiring high degree of expertise!Energy storage system (resonant capacitive system – expensive)Scanning system factor of 30 more rapid orLongitudinal scanning insteadNo size advantage; large cost increase in magnet and RF systemsSize increases for hypofractionation/high dose rates

17. Cyclotrons – General AdvantagesStrengths … By far, the most widely applied hadron-therapy machineCritical considerations for small facility/hospitalFootprint + facility cost; lower power requirementsTurnkey operation and reliable minimal staffing requirements - 10 MIN to BEAM from shutdownSimple Beam ControlResonance or field-driven extraction; CW, rapid beam modulation (generally @ion source)Fixed emittance and beam envelope control as a function of energy (thanks to degrader)Accelerator decoupled from treatment beam, identical X and Y emittances for scanningLowest cost and size, simplicity and reliability, intense beam current, the ability to modulate rapidly and accurately the beam current

18. The only ion therapy cyclotron

19. Degrading Carbon (Y. Jongen, 1st workshop on Hadrontherapy, Erice, Sicily, 2009

20. Cyclotron general commentsFactor of 6 increase in current over slow cycling synchrotronsHigh losses and activation; particularly for hypofractionationsIncreased shielding 15’ 23’Contamination – adding all isotopes ~ 0.1% of treatment beam Lower energies - decreased dose rate.Y. Yongen, 1st workshop on hadrontherapy, Erice 2009The calculated potential residual dose at one foot for 1.6 x 10 13 p/spill at different repetition rates, on 100% interaction length Cu and steel targets for 12, 24, and 1 hour periods of beam followed by a cooling period. Essentially stopping 10 13 p/spill in a degrader– matches technical limits.

21. ADAM Applications of Accelerators and Detectors to Medicine Linear Accelerator (LIGHT + Injector)30-230MeV LIGHT acceleratorPrecision: the system has an active longitudinal modulation along the beam propagation axis (beam energy can be electronically varied during therapy and therefore the treatment depth), rather than using a passive modulation system (where the cyclotrons fixed initial energy is degraded through the interposition of variable thickness energy absorbers between the accelerator and the patient, causing a quality loss of the beam). Moreover, the LIGHT system has a dynamic transversal modulation that allows a precise 3D treatment of the tumours (spot scanning)Missing – achromatic optics for longitudinal scans; beam delivery or retuning optics at isocenter is the limiting factor. Verify energy with each transverse movement?

22. Compact 1-GeV Proton Linac36 mTotal length – 80 metersMost expensive optionLargest footprint4 years to prototype RF cavityNot a vendor accelerator

23. 400 MeV/u Carbon Cyclotron & LinacTERA FoundationAmbitious, long time-scale, costly R&D projectFinal “production” accelerator remains expensive (more than synchrotron)4 years min to prototype RF cavity and modulesNot a vendor acceleratorSupports two ion sources without change-out/1 sec switching time

24. Issues LinacRF system:Very expensive RF system: 1344 total cavities, in 96 tanks with 14 klystrons5.7 GHz C-band RF cavity under development (state of the art)Complex 24-cavity module yet to be designed/prototyped; tight tolerancesStrong high-frequency cavities disrupt transverse linac beam structureVery strong short quadrupole magnets required; not designedCentimeter aperture very small for a hadron beam (~ factor of 5 smaller than typical proton/carbon apertures; this is an electron beam aperture)Cannot be increased and maintain gradient required for footprintSpecification is one RF trip/treatment session – will have to reliably monitor/repaint/compensateCyclotron injector120 MeV/nucleonSuperconducting; not designedExpensive acceleratorDegrader for lower energies?Cannot be matched efficiently to linacMatching section not shown/designedIncompatible beam properties; high losses and activation during transition100 nA of carbon from cyclotron produces only 2-4 nA from linac; insufficient for radiobiologyB1505030021

25. Understanding a ns-FFAGApply a “synchrotron” strong-focusing field profile to each “cyclotron” orbitStrong-focusing allows Long injection/extraction or synchrotron-like straightsStrong RF acceleration modulesLow –loss profile of the synchrotronDC beam to high energies in compact structure400 MeV/nucleon: charge to mass of ½ (carbon)1.2 GeV protonsAvoidance of unstable beam regions constant machine tunestraight =P (MeV/c) or Bfield or normalized path lengthFFAG limit ≥2 GeV protonsCyclotron limit ~ 1 GeV protons

26. Dual Accelerator Patient Model (PSI data*) Below is a model-based treatment using 70 MeV as the lower limit since many nozzles ( or energy degraders)  only work in the 70 to 250 MeV range. (Lower energies can be obtained by plastic range shifters placed close to the skin and aperture, for example with breast, pediatric patients, and parotid tumors in the jaw. )Site   Percentage  Energy Range (MeV)Lung         9%           70 - 170Breast     3%            70 - 140CNS       15%            70 - 150 ( central nervous system, i.e., base of skull & tumors around spinal vertebrae)Rectum   2%            70- 170  ( also cervical cancers may be a few % in this energy range)Pediatric  8%            70 - 150Head & Neck  15%     70 - 150Prostate   45%          200-250Other        2%  This fits nicely with a dual energy accelerator system where E≤150 MeV can be used for roughly 50% of the patients. At PSI all patients were treated with E< 180 MeV excluding prostates. **based on discussions with G. Coutrakon, 2009.

27. Dual-stage ion FFAG proton FFAG with proton CT (pCT)1st stage18 – ~250-330 MeV H- Fixed or swept-frequency RF, DC beamLow intensity for pCTStripping controls extraction energy and intensity in addition to source modulationOR9-~70-90 MeV charge to mass ratio of ½Fixed-frequency RF, DC beam for all ionsVariable energy extractionUpstream injector for high-energy ring2nd stage (~4 m x 5-6 m long)70/90 MeV – 430 MeV/nucleonVariable energy extractionAdjustable, fast orbit bump magnets/extraction septum in long straightDC extracted beamVariable energy on scale of tens of microsecondsInvestigating extracted energy range1st stage: Cyclotron or FFAG2nd stage: 70/90 – 430 MeV/nucleon ionsVariable energy selection:Injection/extraction straight

28. NEXT-generation DC AcceleratorsIsochronous or CW (serpentine channel relaxes tolerances)Stable tune, large energy rangeThe footprint of CW/DC FFAG accelerators is decreasing rapidlyHeidelberg synchrotron

29. Comparison of Accelerator TechnologiesAcceleratorTypeSizeDose RatePer literEnergy ModulationVar / Acc BeamFixed Delivery NC / SCScanTrans /LongSC Synchrotron 40 m (diam)5 Gy/min0.2 Gy/secV1 ms -2 sec10 ms100 msT + Lin cycleRC Synchrotron20 m (diam)x Cycle factor*1.3 Gy/minV1 – 66 ms10 ms100 msL in cycleT cyc to cycCompact Proton SynchrotronHitachi5 m(diam)8 m0.075 Gy/min0.0025 Gy/sec0.75 Gy/min0.025 Gy/secVV1 ms -2 sec10 ms100 msT + Lin cycleLinac/Cyclinac40 -80mAny rateV1 ms10 ms100 msAnyCyclotron6.3 m(diam)5 Gy/min0.08 Gy/secF1 ms10 ms100 msT then LFFAG4m x 6mracetrackAny rateV50 sec 10 ms100 msAny- All ion accelerators can accommodate up to 430 MeV/nucleon carbon; fixed field use charge to mass of 1/2* In principle RCS = cycle time factor x circumference factor x SC Synchrotron dose rate

30. Proton IMAGING: pCT & RadiographyThe same beam used for cancer therapy can make CT images of tumors with ultra-low radiation doses to patient- but requires higher energy protons (250-330 MeV)“protons lag behind conventional radiotherapy in many key ways” On board imaging …Hardware and software advances that improve the precision and efficiency of deliverySteve Hahn, M.D., Chair, Radiation Medicine, Penn Medicine (U. of Pennsylvania)Next generation proton/ion therapy facilities need to support 330 MeV protons for imaging. Present gantries cannot be retrofitted. Compact pCT systems are needed – ultra-low intensities; 1p/sec is present state of the art.

31. SummaryA (slow-cycling + RCS)/2 appears the most promising of the synchrotons but the footprint remains ~20-40 m diameter; longer timescales for beam deliveryThe cyclotron is well developed but degrades 430 MeV/nucleon to treatment energies; causes increased activation and increased shielding footprint and limited dose rate at lower energiesMay be difficult to deliver a treatment and imaging beam simultaneouslyLinacs and hybrids (cyclinac) are the most versatile, but the largest and most expensive and the rapid energy variation cannot be exploited as advertised.FFAGs are close to final engineering and prototypingGantries are another the critical technology; a fixed gantry with multiple extraction ports is under design to reduce the cost/footprint of high energy carbon delivery;