We Protect, Enhance and Save Lives.

Recent developments in

cyclotrons for proton therapy at

IBA

Yves Jongen.

Founder & CRO

IBA sa

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06A typical PT center €30-55 millions for equipment

€45-100 millions for the center€€3030--55 millions for equipment55 millions for equipment€€4545--100 millions for the center100 millions for the center

80-100 m

35 m

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The accelerator is a very small part of a PT system

� A Proton therapy system is much more than an accelerator

� It is most often a complex, multi-room system, filling a Hospital building.

� The treatment rooms are larger than the cyclotron vault

� The total investment is around 100 M€, of which 45 M€ for the equipment

� The cyclotron represents only 7 M€ of this!� The investment to develop the cyclotron was less

than 4 M€, out of more than 60 M€ spent on developing IBA PT system

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06Proton Therapy end of 2007

PT center under operation

Courtesy Janet Sisterson & PTCOG

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NCC, Kashiwa

MGH, Boston

MPRI, Indiana

UFPTI, Jacksonville, FL

Beijing, China

NCC, Ilsan

WPE, Essen

13 IBA PT customers in the world

Orsay (France)

ProCure 2 Chicago

Hampton Univ., Virginia

Wanjie, China

U.Penn, Philadelphia

ProCure 1Oklahoma City

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06IBA has currently the largest installed base in PT

PT Installed base shares - PROTON -(1994-2008) in ROOMS

IBA60%Hitachi

13%

MHI13%

Varian7%

SHI3%

Still River4%

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06Cyclotrons for Proton therapy?

� In 1991, when IBA entered in PT, the consensus was that the best accelerator for PT was a synchrotron

� IBA introduced a very effective cyclotron design, and today the majority of PT centers use the cyclotron technology (not only IBA but Varian, Still Rivers)

� Over these 15 years, users came to appreciate the advantages of cyclotrons:�Simplicity�Reliability� Lower cost and size�But, most importantly, the ability to modulate rapidly

and accurately the proton beam current

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06Proton beam current regulation

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06Change of energy?

� Cyclotrons are simpler at fixed energy� Energy change by graphite/beryllium degrader at

waist after cyclotron exit, followed by divergence slits and energy analyzer

� This very effectively decouples the accelerator from the patient

� Unlike the synchrotron, the emittance is identical in X and Y. This makes gantry optics much easier in scanning mode

� Yes, neutrons are produced, but ESS is well shielded and the average beam current in PT is low > limited activation

� How fast? 5 mm step in energy in 100 msec at PSI (vs. 2 sec for IBA or 4 sec. for a synchrotron).

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06The IBA ESS

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06More ExpertiseThe energy selection system

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06More ExperienceUFPTI, Jacksonville, USA

• Construction start date: Mar 2004• PT equipment installation start: Mar 2005• 1st Patient : Aug 2006 ! • today : 130 patients/day treated in 3 Gantry rooms• up to 250 fields/day

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06The UPHS Particle Therapy Centre, Philadelphia

•The largest Particle Therapy centre to date!• 4 Gantry Rooms•1 Fixed Beam Room (2 beams) + 1 Experimental Room• Beam since July 2008• First patient treatment in Autumn 2009

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06Procure center #1, Oklahoma city, USA

• First center of the Procure network• 2 Gantry Rooms• 1 Fixed & Inclined Beam Room• Beam since July 2008• First patient treatment in Autumn 2009

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06Hampton University Proton Therapy Institute

• 4 Gantry Rooms• 1 Fixed Beam Room• All equipment installed• Beam accelerated in the cyclotron

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06Westdeutsche Protonentherapiezentrum, Essen

• First Particle Therapy centre based on a Public Pri vate Partnership (PPP) model•3 Gantry Treatment Rooms•1 Double Fixed Beam Room with Eye Treatment line• Beam since September 2008• First patient treatment in Autumn 2009

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06New cyclotron and gantry for CPO in Orsay

• New equipment for an existing PT center• New cyclotron, ESS and one new gantry room• Transition to be made without interrupting treatmen ts !!!!!• 2 existing Fixed Beam Rooms• All equipment installed, cyclotron beam extracted, optics tuning ongoing

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06C230 median plane view

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06C230 in numbers

� 230MeV, 500nA proton beam for therapy� Resistive but high field magnet: 2.9T peak field, 1.1m

extraction radius, 4 spiral poles, elliptical gap, 800A, 524 kA-turns, 9mm pole gap at outer radius

� Internal hot filament PIG source� RF system: 106MHz 100kW, harmonic mode 4, dee

voltage from 60 kV at the center to 120 kV at extraction

� Electrostatic deflector extraction

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06More ExpertiseThe CYCLONE 230 cyclotron

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06The cyclotron opens at median plane for service

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06Inside the cyclotron

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06The ion source and central region

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06Electrostatic deflector

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06Recent improvements on the C230

�15 C230 cyclotrons have been built, but we keep adding improvements. Recent developments include:�Correction of slight tilts in the orbit plane

�Design improvements in the RF cavities�New deflector design

�Improved beam current regulation

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06Recent improvements on the C230

�15 C230 cyclotrons have been built, but we keep adding improvements. Recent developments include:�Correction of slight tilts in the orbit plane

�Design improvements in the RF cavities�New deflector design

�Improved beam current regulation

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06RF cavity redesign

� Problem:Due to the elliptical pole shape, the counter-dee gap decreases with radius.

� Consequence:Beam losses on counter-dees at large radius.

� Solution: Maximize the counter-dee gap.

� Method:Redesign the RF cavities to increase the counter-dee gap from 10mm to 12mm.

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06RF cavity redesign

� New cavity design

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06RF cavity redesign

� New cavity design

Redesigned area

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06RF cavity redesign

� New cavity design

230MeV orbit

12mm

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06RF cavity tuning redesign

� Problem:The present cavity tuning by a variable capacitor in the median plane needs periodic replacement. It is difficult to share the larger RF current drawn by this capacitor equally in the upper and lower cavity.

� Consequence:Capacitor failures: loss of reliabilityLack of up-down symmetry: leaks of RF in the cyclotron through the accelerating gaps

� Solution: Tune the cavities with inductive tuners in the valleys sliding on RF contacts

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06New cavity tuner design

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06Electrostatic deflector optimization

� Problem:The ‘old’ septum intercepted a significant amount of beam.

� Consequence:Activation, limited extraction efficiency…

� Solution:Reduce septum beam apparent thickness.

� Method:Analytical study and beam tracking. Then build it and try it!

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06Electrostatic deflector optimization

� Beam tracking simulation of ‘new’ deflector.

Pole edge

Circulating beam

Extracted beam

Deflector

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06Electrostatic deflector optimization

� Beam tracking simulation at JINRComparison between ‘old’ and ‘new’ septum :

1%0%Losses inside deflector on HV plate

1%8%Losses inside deflector on septum

9%28%*Losses on septum entrance (0.1mm)

‘New’‘Old’

* plus circulating beam

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06Electrostatic deflector optimization

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06Experimental results

� Radial track using integral radial probe

Beam currenton externalbeam stop

(Raw data, not corrected for RF noise and radial probe efficiency.)

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06Experimental results

� Radial track using integral radial probe

Adj. dowel pinsNew RF cavity

Adj. dowel pinsNew RF cavityNew deflector

Integral radial probe beam current External beam stop current

Def

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06Proton beam current regulation optimization

� Present situationThe proton beam current is slaved to an external time function by measuring the extracted beam with an ion chamber, doing a digital regulation by varying the arc current in the ion source. The current loop regulates the beam current with an accuracy better than 2%, up to a bandwidth of 2.5 KHz

� Problem:We have a “dark current”. Even when the arc is turned off, a proton beam current of 30 to 100 picoampere is extracted from the cyclotron

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06Proton beam current regulation optimization

� Consequence:The dark current results in small inaccuracies in beam delivery. In pencil beam scanning, it can result in small amounts of beam being delivered outside the treatment field

� Solution:Use a reduction of the dee voltage to suppress the proton beam when it is not needed. Possibly, use the dee voltage variation exclusively to regulate the beam current

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063 kV dee voltage variation is enough

Beam current vs Dee Voltage

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22/11/2007 11:30

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06Modulating the dee voltage by 3 kV at 62 kHz!

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06Regulating 500 µsec pulses

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06Data analysis on IC cyclo, 4 nA peak

Regulation triangle 100 Hz 4 nA

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Series1Linear fit

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Thank you…