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Particle Beam Technology and Delivery

AAPM Particle Beam Therapy Symposium

Flanz 2013; AAPM Symposium Types of Accelerator Systems

Laser Linac Cyclotron

Rf Linac FFAG CycFFAG

CycLinac Isochronous Strong Cyclotron Focusing

DWA Weak Synchro- Focusing Cyclotron Rock Rapid Mackie Cycling Vladimir Jay Flanz Derenchuk

Flanz 2013; AAPM Symposium 2 Particle Beam Technology & Delivery

Synchrotrons

J. Flanz, Ph.D. Massachusetts General Hospital Harvard Medical School

Flanz 2013; AAPM Symposium 3 Ongoing Themes in Field of Particle Therapy Examples for CONTEXT of Technology and Delivery: 1. Pencil Beam Scanning (PBS) – Impact on: Beam Parameters from Accelerator + Delivery – Scanning “type”; Beam Size; etc. 2. Image Guided Therapy (IGRT) – Impact on: Imaging; Beam Alignment – Radiography/Tomography ???? X-ray Simulation Proton Radiography 3. Organ Motion Simulation – Impact on: Beam Parameter timing; Beam Tracking Joao Seco, MGH 4. End of Range ® - Proton Range vs. HU ? 5. Field Directions(θ,ϕ,ψ): How to treat specific sites? 6. Lower Capital Costs $$$ 7. Increased Throughput – Positioning, Aligning, Field-to-field time, Beam time These may not be new concepts, but they are the current foci owing to the fact that the ‘first’ round of system specs have been satisfied. (i.e. the Berkeley/MGH report of 20 years ago.) Flanz 2013; AAPM Symposium 4 Separated Themes may not lead to system solutions! Need System Solutions • How to deliver a Rx non-uniform dose distribution to a moving target with a desired conformance? vs. e.g. Continuous Beam Scanning: with 3mm Sigma – This involves beam parameter TIMING issues, beam trajectory and range manipulation, Apertures (or not), etc. • How to deliver quality treatment to the appropriate number of patients at an affordable cost? vs. e.g. Out of room setup; Energy Change in 2 seconds – This involves automated remote operations • Imaging and Analysis and Correction of Position • Go from Field to Field without delays (e.g. Moving things remotely)

It’s not just the accelerator. It’s the other components and how the accelerator works with the other components !

Flanz 2013; AAPM Symposium 5 Goal of Particle Radiotherapy • Deliver required dose to a target in a reasonable time • Deliver the correct dose distribution to the correct location – Minimize the dose outside the target

Dosimetric Regions of Interest (Scattering)

A B

C Use this as the

Depth Direction building

D E blocks to

E deliver dose

Transverse Direction • C&D = desired dose • E, B&part of A= desired dose • A+B+E = unwanted dose • Some of A+(C-E) = unwanted dose 6 Flanz 2013; AAPM Symposium Spread out Transverse Dose with Scanned beam spots Y0 Y0 Sharp EdgedY0 1.2 Asymmetric 1.2 Gaussians1.2 are Magic

1 1 1

0.8 0.8 0.8

0.6 0.6 0.6

0.4 0.4 0.4

0.2 0.2 0.2 0 0 0 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 -8 -6 -4 -2 0 2 4 6 8 -0.2 -0.2

Transverse spreading using superposition of unmodified beams. Uniform dose scenario.

Spacing: 2 sigma 1 sigma 2 sigma Spacing: Flanz 2013; AAPM Symposium 7 Scanning – The “Penumbra” of a scanned beam Small beam sigma vs. Cut off edges.

1.2

1

0.8

0.6

0.4

0.2

0 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 -0.2

PSI/Berkeley In this case the Technology required has to produce a In this case the Technology different beam profile (where it required has to deliver a dose counts). modulated distribution Flanz 2013; AAPM Symposium 8 Materials in the Beam Path – Including the Patient The Raw beam shape is NOT the only contributing factor

Range Shifter

Stefan Schmidt

4.5

18

9 Flanz 2013; AAPM Symposium Dose / Dose Rate • Power = Joules/sec = Energy * Current – e.g.  150 MeV * 1 nA = 0.15 Watts • Dose = Joules/kg ≡ Gray (Gy) – Dose = (Power* seconds) /kg – e.g.  150 MeV * 1 nA * 60 sec = 9 Joules • Water  1kg/1000cc = 1kg/liter • Dose = 9 Joules /1kg (in a liter) •  150 MeV, 1nA == 9 Gy in 1 liter in 1 minute • But not all energy goes into the target (see Bragg peak) 3-6 Gy in 1 liter in 1 minute

• Therefore, for 1Gy in 1 liter we need ~ 120 GigaProtons – (120 GP/min  ~ 0.3nA)

Flanz 2013; AAPM Symposium 10 What is a Synchrotron?

Energy

#

Time

Flanz 2013; AAPM Symposium 11 Ring Orbit – Alternating Focusing

Focusing elements Unperturbed closed orbit

Perturbed a little - closed orbit

Perturbed a lot - closed orbit

Flanz 2013; AAPM Symposium 12 Synchrotron Beam Dynamics

Flanz 2013; AAPM Symposium 13 Resonant Extraction (one method)

6

5 Linear

Octupole 4 θ Extraction 3 Septum

2 Field Strength 1

0 0 0.5 1 1.5 2 Horizontal Displacement • The process is partly stochastic (uncorrected time structure is not smooth)and • The extracted beam phase space is NOT Gaussian in the extraction plane (depending on the type of extraction). x Flanz 2013; AAPM Symposium 14 Beam size from the last to Isocenter?

Gantry/ Dipole

Isocenter

Gantry Dipole Power / Weight 12

10 PS Current ~ Gap (2.1 sigma) 8 2 Magnet weight ~ gap 6 2 2 Power ~ Current ~ gap 4 Dipole Power/Weight Dipole 2

0 2 4 6 8 10 1 sigma Isocenter Beam Size 15 Flanz 2013; AAPM Symposium Treatment Time Contributions Synchrotron • Time to Inject Tb • Time to Accelerate To • Time needed to wait until the patient is ready for particles (e.g. gating) • Time needed to extract particles – Instrumentation will only allow a finite number of particles per unit time If more particles are needed are needed more particlesIf or change energy • Time needed to Decelerate Additional ‘cycle’ times are needed if there are not enough protons in the ring to deliver the required dose at a given range. Flanz 2013; AAPM Symposium 16 Time needed to wait until the patient is ready for particles

Breath

Variable Cycle Synchrotron Beam Available Fixed Cycle Synchrotron or Cyclotron Beam Available

CW Cyclotron Beam Available

Okay to Deliver Beam Comparison of Beam Utilization for Treatment Requiring Synchronization Effective Dose Rate may depend upon accelerator time structure

Flanz 2013; AAPM Symposium 17 Are additional cycle times needed? : Space Charge effects How many protons can be stuffed into a Ring? Charges ⇒y repulsion Parallel currents ⇒ attractive Gaussian + + + + ++ ++ + density ++ + ++ + ++ + ++ + ++ +++ ++ + + + + distribution + ++ ++ +++ + ++ ++ + + + ++ + +++ ++ + + + + + ++ + ++ ++ ++ ++ + x + ++ + + +++ + ++ + + + + ++ +++ + ++ + + + ++ + +++ ++ + + + + + ++ +++ + + ++ + + +++ ++ + + + ++ + ++ Linear + + Defocusing Coulomb force

x

Non-linear

Flanz 2013; AAPM Symposium 18 How many protons can be stuffed in a ring? How many are needed? Proton Limit in Ring due to Space Charge Effects

1.60E+11

1.40E+11 LLUMC MDA

1.20E+11

McLaren 1.00E+11

8.00E+10

6.00E+10

Extracted Current (na) Current Extracted Assumptions: A finite cycle time 4.00E+10 High Efficiency Extraction Beam Size 2.00E+10

0.00E+00 0 2 4 6 8 10 12 Proton Injection Energy (MeV)

Also 1Gy/min in a liter  113GigaProtons/min  <3Gp/cycle Flanz 2013; AAPM Symposium 19 First Proton Therapy

LLUMC, Tsukuba, MD Anderson, Shizuoka, Wakasa, HIMAC, Hyogo, McLaren, Mayo …

Hitachi Extraction 20 Flanz 2013; AAPM Symposium 20 Faster/Bigger Synchrotron Extremes Smaller / Cheaper Rapid Cycling Medical Synchrotron “Compact” Medical Synchrotron the second generation Synchrotron accelerator

Gantries

Accelerator Physics VS. ANTI-Accelerator Physics? • Current (~

Remember: 400MeV/nucleon:

Could be big and Expensive! But they are shrinking also !

Heidleberg NIRS Japan

Flanz 2013; AAPM Symposium 22 What might someone do with a Blank Slate? • How to deliver a Rx non-uniform dose distribution to a moving target with a desired conformance? – Scanning beams with adjustably sharp edges – Accelerator with timing consistent with Scanning and organ motion (Flexible timing) – Appropriate on-line imaging • How to deliver quality treatment to the appropriate number of patients at an affordable cost – Accelerator Design: • Make it INEXPENSIVE, Simple – Design only what’s needed » What Energy is needed? (Treatment, Tomography, … ) » What Current is needed? (Scattering, Scanning, Losses …) • Simplify the Optics – Minimize Building costs; e.g. Some Shielding Requirements • No ‘designed’ sources of BEAM LOSS – Chose a Beam delivery like Scanning

Flanz 2013; AAPM Symposium 23 Gratuitous Comments:

• Treating with particles requires a system approach. • The various subsystems interact with each other and depend upon each others capabilities. • Trade-offs include size, speed, intensity, of everything, (equipment, beam etc.) • More and more demand for affordable particle therapy solutions is apparent. • New Approaches are being fueled by both accelerator interests, and by the more and more demanding requirements of particle therapy.

24 The Francis H. Burr Proton Therapy Center

Thank You ! 25