synchrotron technology for proton beam therapy

Synchrotron Technology for Proton Beam Therapy

Kazuo Hiramoto

Power & Industrial Systems R&D Laboratory,Hitachi, Ltd.

PTCOG 46 Educational Workshop

May 18, 2007 PTCOG Educational WS HITACHI, Ltd.

Synchrotron Based System

Synchrotron:RF CavityBending andQuad. Mag.

Injector:LNAC

Beam Transport

Irradiation System: (RotatingGantry )

Synchrotron Based Proton Therapy System

Injector : LINAC or Electrostatic Accelerator

Synchrotron : Acceleration and ExtractionHigh Energy Beam TransportIrradiation System


Classification of Synchrotrons

Rapid Cycle• Operation Period : < 0.05 s• Fast Extraction : 10-6 Sec• Energy : Variable( in Principle),

or Changed with Degrader• Energy Spread : >> 0.2%

Injection

Time

Dec.⊿

E

Accel.

Spill Length 10-6 Sec.

Slow Cycle • Operation Period : > 1s• Slow Extraction :

Variable Length and Intensity•Energy : Variable • Energy Spread: Small< 0.2%

Time

Injection

AccelelationDecel.

Spill Length

E

Variable



00.10.20.30.40.50.60.70.80.9

0 50 100 150 200 250 300 350

Dose

Depth

Intrinsic Features of Slow Cycle SynchrotronAcceleration to Higher Energy for Necessary RangeVariable Energy without Degrader

- Fine Energy Resolution- with Keeping Beam Current - without Unnecessary Radiation

Small Energy Spread for all the Energy : Good Distal Fall-off


Synchrotron Based SystemIntrinsic Features of Slow Cycle Synchrotron

After the first application to LLUMC in 1990, which was the first hospital based proton therapy system, slow cycle synchrotron have been widely applied to proton and carbon therapy systems .

Application of Synchrotrons to Particle Therapy Systems

Acceleration to Higher Energy for Necessary RangeVariable Energy without Degrader

- Fine Energy Resolution- with Keeping Beam Current - without Unnecessary Radiation

Small Energy Spread for all the Energy : Good Distal Fall-off


Weak Focusing Synchrotron

An Example of Lattice(LLUMC)

• Use of a Trim Quadrupole- One Dimensional Control

of Betatron Tunes

• Combined Function Magnet- Bending with Focusingand Defocusing Function

- Compact Size Lattice- Large Orbit Deviation

by Energy Difference

• Application-LLUMC, Shizuoka


• ApplicationP: MDACC, Tsukuba,

WakasaP, C: Hyogo, HICATC : NIRS

• Use of Quads QF and QD: - Flexible Control atInjection, Accelerationand Extraction

- Small Orbit Deviationby Energy Difference

Strong Focusing Synchrotron

7m

R1.4m

Injectionfrom Linac

Extraction to Beam Transport

BM

ESD

SX

QF

QDRF-forAcc.

An Example of Lattice • Separated Function Magnets- Bending - Quadrupole


39m

2 TreatmentRooms with

RotatingGantries

Exp. RoomSynchrotron(70-250MeV, Slow Cycle)


- Wakasa Bay: P, He, C (Multi Purpose) ( 2000)

- PMRC, Univ. of Tsukuba: P (2001)

- MD Anderson Cancer Center : P (2006)


Fixed Beam

SynchrotronLinac

MDACC SystemSynchrotron (70-250MeV)




Gantries (Passive)Gantry

(Scanning)

Medical Synchrotron SystemsSynchrotron Based System


Low-energy Beam

Irradiation Room

Medium-energy Beam Irradiation Room

Synchrotron

High-energy Beam

Irradiation Room

Medical Irradiation

RoomTandem type Electrostatic Accelerator

Injection

Extraction

Synchrotron(P: 200MeV, He,C: 55MeV/u)






Typical Performance

TimeInjection

AccerelationDecel.

0.5 – 5 secExtraction

E

Performance•Proton Number : 1011 / Pulse•Acceleration : 70 – 250 MeV• Variable Energy:

Resolution < 0.4 MeVControlled without Degrader

• Energy Spread: •Beam Extraction: Variable Timing and Variable Duration

⊿E/E <0.2%

Developed Technology• RF Acceleration: Digital Control and Low Power RF

• Beam Extraction : Application of Transverse RF


RF Acceleration Technique

Fundamental+

HarmonicsRF PowerAmplifier

B-Field Bending Injection

ExtractionBeam

MonitorFrequency

VoltageControl

RF Oscillator

(DDS)

VoltageSignal

RFControl

Beam PositionSignal

SignalProcessor

RF Cavity

70-250 MeV

Acceleration System:1. Wide-band RF Cavity

3. Digital Frequency Control2. Solid Power Amp.

•Simple and Reliable •Fine Energy Resolution•High Reproducibility


Wideband RF Cavity

450 mm

Multiple Power FeedingImpedance matching betweenRF cavity and RF power source

accelerating gap

Multi-channel Solid-state

RF Amplifier

FINEMET Core•High complex permeability for Freq. Range 1-10 MHz •High Curie temperature

Reliable OperationReliable Operation

•Solid-sate Amp. •Air Cooling

Simple Operation• Non Resonant Freq.


RF Acceleration System of HICAT

RF Cavity

RF Power Amplifier

RF Control System RF Cavity Design Parameters

Frequency

Accel.Voltage > 2.5 kV

Magnetic Core FINEMETPower Feeding Each Core

Length 1.4 m1-7 MHz

RF Amp. Power 6 kW

Particles P, He, C etc.Accel. Energy P:250MeV,

C:430MeV/u


Application to Fast Energy Change

Range modulation for scanning with pulse to pulse.

0 4 8 12 16 20t[sec]

155MeV 150MeV 145MeV 140MeV 135MeV

Pulse to pulse energy change

Synchrotronoperation

pattern

Extraction

Injection

IrradiatedBeamsignal

Fast Parameter Change for Different Patient


Beam Extraction : Magnet Current Change

Extraction : Narrow the stability limit of betatron oscillations

Stability Limit

No Extracted Beam

Beam Duct of Synchrotron

Prior: Beam circulating with stable oscillations before extraction

Beam

Beam Extraction Line (with Electric Field)

Extracted Beam in various tracks

Time

Time

On Off

QF : QuadrupoleFocusing magnet

ESD : ElectrostaticDeflector

BMP : Bump magnetSynchrotron

NozzleNozzle

PatientPatientRotating Beam

QF ESD

BMP

Slow Beam Turn On/Off

Beam Position Fluctuation

QF

ESD

BMP

ExtractedBeam

Intensity

Beam

Stability Limit

Magnet Current Change for Narrowing the stability limit


RF Driven Beam Extraction

Extraction : Applying the RF to make the beam exceed the stability limit

Stability Limit

No Extracted Beam

Extracted Beam in Single Track

Stability Limit

Beam Extraction Line (with Electric Field)

Beam Duct of Synchrotron

Prior: Beam circulating with stable oscillations before extraction

Magnet Current : Constant

Sufficient Beam Position Stability

Beam Position TimeBeam

Synchrotron

NozzleNozzle


QF ESDStable Beam Position

BMP RF forExtraction

TimeOn Off

BMPQF

ESD


RF

Time

Variable Spill Timing and IntensityBeam

Intensity

Sufficient Beam Position Stability

Beam Position Time

pow

er

frequency

f0±Df

RF Amp.

•Beam on/off and intensity is controlled by the applied RF power.

• Applied frequency f0 is varied withthe beam energy.

Beam Duct RF

Electrode

RF Driven Beam Extraction

Synchrotron

NozzleNozzle


QF ESDStable Beam Position

BMP RF forExtraction


Beam Performance

200µs

(Averaged 33times)RF gate signal

Switching time(OFF)<150µs

Time [50ms/div]

Bea

m P

ositi

on[m

m]

-0.5

0.5

0.0

Hori.

Vert.Within 1 spill beam extraction

1ms Time-resolution

0 200 400 600 800time[ms]

Inte

nsity

[arb

.] Beam Gating

Time [1hour/div]

All of the operating parametersare kept constant for 10 hours.

Hori. Vert.0.5

0.0

-0.5

Bea

m P

ositi

on[m

m]


Stability for Energy Switching

Mea

s. B

eam

Pos

ition

[mm

]

Time from G1 Beam on (min)

-0.5

0

0.5

1

0 2 4 6 8 10 12

G1200MeV

G2250MeV

Fixed225MeV

G1200MeV

G2250MeV

Fixed225MeV

- High Position Stability and Reproducibility for Energy and Course Switching


Irradiation Scheme of Synchrotron Based System (1)

Beam

Scatterer

Wobbling Magnets

Wobbling system

Beam1st. scatterer

2nd. scatterer

Passive scattering system

collimatorcollimator

y

dose

•Tsukuba • MDACC

• Wakasa Bay• Hyogo ( Proton and Carbon )• NIRS (Carbon)


Irradiation Scheme of Synchrotron Based System (2)

- P : MDACC - C, P : HICAT

• Lateral : Pencil Beam Scanning

Range modulation

TargetSpot

Beam

Layer

• Distal : Pulse to Pulse Energy Change by Synchrotron


Respiration Synchronized Operation

ExtDec

InjAcc

ExtDec

Wait Wait

InjAcc

Wait Wait

Synchrotron pattern Variable Repetition Period

tInjection,Acceleration Deceleration

Extraction

Flat-top

Injection Wait for ExtractionTrigger

Inspiratory

Expiratory

ExtractionTrigger

RespirationSignal

SynchrotronPattern

ExtractedBeam

• The flat top is extended and the beam extraction is gated by therespiration signal.

• Prevention of longer treatment due to non-periodic respiration.

Operaion Cycle Length


Respiration Synchronized Operation• The flat top is extended and the beam extraction is gated by the

respiration signal. • Prevention of longer treatment against non-periodic respiration.

Respirationsignal

Extractiongate signalSynchrotron

operationpattern

Irradiatedbeam

2sec

Wait fortrigger

Wait fortrigger

Inspiration

Extraction

Variable repetition rate Injection


Stability for Various Repetetion Periods

Synchrotron pattern

tInjection,Acceleration Deceleration

Extraction

Flat-top

Injection Wait for ExtractionTrigger

• The flat top is extended and the beam extraction is gated by therespiration signal.

• Prevention of longer treatment against non-periodic respiration.

Repetion Period

x(Hori.)y(Vert.)

0 50 100 150 2000

5

10

-1.0

-0.5

0

+0.5

+1.0

Rep

etiti

on

Peri

od[s

ec]

Bea

mPo

sitio

n[m

m]

Time from treatment starts[sec]

Variation<±0.2mm

Repetitionperiodsvariedfrom 2.8sto 10.5s

Interval time =repetition period


Summary

The slow cycle synchrotron has advantages for energyand dose controllability and also small energy spread.

Slow cycle synchrotrons have been widely applied to particle therapy systems over past 17 years with highreliability and availability. For example, the MDAsystem is being operated with the availability of 98%.

New technologies for beam acceleration and extractionhave been applied to new irradiation schemes for therespiration gating and pencil beam scanning.

synchrotron technology for proton beam therapy

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