Recent progress in cyclotrons for protontherapy at IBA
Transcript of Recent progress in cyclotrons for protontherapy at IBA
Recent Developments
in Proton AcceleratorsAccelerators
Damien BERTRANDDomain Expert Hadrontherapy
Erice Workshop on HadrontherapyMay 20-27, 2011
C230 key specifications
� Compact isochronous cyclotron
� 235 MeV proton energy� 300 nA beam current, quasi-continuous� Typical efficiency : 55 %
© 2
006
� Approx. weight: 220 T� Diameter: 4.3 m
� Conventional magnet coil: 1.7 - 2.2 T � RF Frequency: 106 MHz� Dee voltage: 55 to 150 kV peak
3
A quite popular solution… ©
200
6
4 20 facilities including IBA equipement, 64 treatment rooms in total
Quite robust design
� Design not changing� Improving tools and technical details for
� Increased reproducibility � Easier maintenance� Faster commissioning
© 2
006
7
Improvements on PBS
Sigma @ 230 MeV
Minimal Energy
Position Accuracy
PBS V1 (UN) PBS V6 (DN)
10 mm 3 mm
140 MeV100Mev
or60 MeV (Optionaly)
+/- 2 mm +/- 1 mm
© 2
006
12
Position Accuracy
Commissioned Angle
Treatment Time
+/- 2 mm +/- 1 mm
0°°°° , 360°°°° All angles
Above 5 min 1 min 36 sec
Switching Time 2 min 15 s
1st patient treatedin Boston, Dec. 2008
PBS Quality Assurance challenges
� A number of parameters to control and validate
- Spot Size (sigma, skewness)
- Spot Position
- Complex shape size analysis
© 2
006
- Complex shape size analysis
- Dose/Intensity analysis
- Range analysis
14
IBA’s Solution : QA test pattern©
200
6
15
Transversal 2D measurements performed using Lynx scintillator from IBA DosimetryData acquisition and processing managed by OmniPro software from IBA Dosimetry
PBS Performances
� Gantry angle dependencySpec beam reproducibility ≤ ± 5%
Beam sigma in air at isocenter vs Gantry angles
2,50
3,00
3,50
© 2
006
19
0,00
0,50
1,00
1,50
2,00
0 50 100 150 200 250 300 350
Gantry Angle (°)
Bea
m s
igm
a (m
m)
Sigma X
Sigma Y
-5%
+5%
Beam Spot for energy of 230 MeV in air @ Isocenter for various gantry angle
Reducing irradiation time: PBS -10s
� Objective: treat a 1-liter tumor with PBS in 10 sec .
� Idea: use patient-specific micro ridge filter
Layer 1Layer 2
Layer N
© 2
006
22
Mono-energetic Beam
Towards a novel, low -cost PT accelerator
� Lower cost & standardized Proton Therapy System
� Compact treatment room and small footprint
� Shorter installation time on site
� Operator less
© 2
006
24
� Reduced maintenance
Proteus One : low cost, smaller footprint
Towards a more compact cyclotron
� Compact machine requires higher magnetic field�Superconducting magnet
� To conserve isochronism one has to compensate relativistic mass increase�Magnetic must increase with the radius
� Increasing magnetic field is naturally defocusing�Restore focusing by alternating field gradients in hills and valleys
© 2
006
26
�Restore focusing by alternating field gradients in hills and valleys� Further increase focusing by spiralling the poles
� … but once the pole iron is saturated, there is a limit on the field gradient between hills and valleys (flutter)
� … and there is also a limit in spiral designs
S2C2 rationale
� The only solution to increase the magnetic field while conserving the beamfocusing inside the machine is to use weak focusing
- No field gradients between hills and valleys- Decreasing field with radius
� With such design isochronism cannot be maintained- Changing RF- Pulsed beam at machine exit
© 2
006
27
- Pulsed beam at machine exit
By definition such machine is a SynchroCyclotronWhich in our case will be Super - Conducting
S2C2
S2C2 Specifications
� Compact system: diameter 2.5 m, height 2 m, weight <50 T� Reliability: NbTi cryogen free coil, passive magnetostatic extraction…� Repeatability: Standard high quality laminated steel� Operability: Operator-free system, remote diagnostics
� 20 nA average beam current at 230 MeV for PBS; 150 nA feasible if required� Extraction efficiency >50% at 230 MeV
© 2
006
29
� Extraction efficiency >50% at 230 MeV� 1 kHz beam pulse repetition rate for PBS� Still possible to reach 250 MeV (with some additional work)
Overall view
Size and weight within specs Easy accessibility on sub-systems
© 2
006
30
Yoke shape compromise : sustainablestray field for ancillary equipments
Making PT more accessible
19 m – 62.3 ft
27.3 m – 89.5 ft
7.3 m 12.8 m
Approx. the size of two linacs
© 2
006
39
7.3 m24 ft
12.8 m42 ft
Proteus ONE* Timing
Projected Product Introduction Timeline
2011 2012 2013 2014
© 2
006
42
Design FreezeSubsystems Procurement
PrototypeTesting
FDA Filing
PatientTreatments
*Subject to review by Competent Authorities (FDA, European Notified Bodies, et al.) before being put on the market.