introduction to gantries and comparison of gantry design
TRANSCRIPT
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Introduction to Gantries and Comparison of Gantry Design
Marco Pullia, CNAO & Frank Ebskamp, Danfysik
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Introduction to CNAO and Danfysik
Gantry designs for protons and carbon ions
Isocenter, multi-room, Riesenrad configurations
Compact gantry design
Carbon gantry: superconducting vs room-temperature
Conclusion
Overview of presentation
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CNAO: National Center of Oncological Hadrontherapy
Synchrotron, three treatment rooms, protons and carbon ions
Operational since 2011
Treated >1000 oncological patients, full CE certification
Danfysik: particle accelerator components and systems
3 complete C+/P particle therapy systems in Marburg, Kiel and Shanghai in collaboration with Siemens
Integrated in the medical ”front end”
Accelerator uptime >95% since November 2013
Collaboration Danfysik & CNAO for new carbon PT projects
CNAO and Danfysik PT history
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Danfysik PT accelerator
• Proven concept (Shanghai, HIT, Marburg)• Flexible, (layout, ions, rooms)• Horizontal, vertical and 45 degree beams• Modular concept• Quick installation (8-10 month)• Service obligations 10-15 years
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What is a gantry
A gantry is a section of beamline that can rotate around the isocenter in order to direct the beam onto the patient from any direction
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Why a gantry ?
To treat patients in supine position (eventually prone) in the same position in which CT, PET and MRI were acquired. Patient rotation only around gravity to preserve internal organs and soft tissue geometry
To provide the maximum flexibility in selecting the irradiation direction when optimising the dose delivery
To allow a “robust” treatment planning. Exploiting the sharp distal fall off can be risky in some cases and a gantry helps in avoiding fields directed towards an Organ At Risk (OAR)
Avoid density heterogeneities
Minimize SOBP extension (less energies required and better peak to plateau ratio)
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Why a gantry ?
Allows better, more robust planning:e.g. minimize fields pointing towards OAR (Organ At Risk)
O.A.R.
With gantryWith horizontal line only
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Gantry in conventional radiotherapy
The whole linac is insidethe gantry
The gantry head can pass between patient and floor for irradiation from below
(Varian Clinac IX)
2.6 m
3.5 m
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B
vF
r q
pB
mvBqv r
r
2
0.2998 B [T] r [m] = p [GeV/c]/q [e]
“Zero comma c”
In practical units:
Electron, 20 MeV: Br = 0.068 T m
Protons, 60 MeV: Br = 1.14 T m
Protons, 220 MeV: Br = 2.27 T m
Carbon, 120 MeV/u: Br = 3.26 T m
Carbon, 430 MeV/u: Br = 6.63 T m
Magnetic rigidity
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Conventional RT
Proton GantryBr < 2.4 Tm
Carbon Ion GantryBr < 6.6 Tm
Deep pit under the patient
Size and magnetic rigidity
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Proton gantries
Mitsubishi
Hitachi
IBA
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Proton gantry geometries
(Adapted from a slide of J. Flanz)
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Carbon gantry
Only one C gantry worldwide: L = 25 m x f = 13 m, 600 t
(Udo Weinrich, GSI)
360° rotationParallel scanning200 mm x 200 mm field140 t magnets120 t shielding-counterweight600 t total rotating mass
Very large, very heavy, very expensive
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Carbon Gantry
The HIT Gantry:the only clinical C Gantry
L = 25 m x f = 13 m,
600 t rotating mass
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NIRS Gantry
Ion kind : 12C
Irradiation method: 3D Scanning
Beam energy : 430 MeV/n
Maximum range : 30 cm in waterScan size : □200×200 mm2
Beam orbit radius : 5.45 m
Length : 13 m
(Courtesy of Y. Iwata)
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NIRS Gantry
Progressively increasing aperture
Combined function,Superconducting magnets
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FFAG Gantry
(Courtesy of Dejan Trbojevic)
CARBON GANTRY height 4.091m
What if dispersion is so small that Dp/p = ±35% goes through? p 142 MeVC 245 MeV
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Chair
Alternatives
Hyogo
CNAO(for eye treatment)
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Cradle couch at HIMAC
Alternatives …
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Multi room system
Proposed by A.Brahme
0 5m 10m 15m0 5m 10m 15m
1 -90<f<-30
2 -30<f<30
1 -90<f<-30
3 30<f<903 30<f<90
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Planar system
Proposed by M. Kats
Circular exit face withcenter on beam entry position. Exit edge angleequals half bending angle.
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Mobile isocenter gantry
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AVO / TERA: Linac Image Guided Hadron Technology
Low cost, compact, modular
LIGHT systems planned for UK and China
LIGHT: linear PT Gantry system
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Integrated accelerator and gantry in one
Proton energy range 70 – 250 MeV
3He energy Range: 410 MeV (137 MeV/u)
Equal to 10 cm penetration
Rotating gantry with a rotation angle larger than 240°
Synchrotron based accelerator:
Energy variation without degradation of the beam
No radiation from Energy reducing degrader
Optimized for protons and Helium ions, No other compact system can provide Helium
Inter-treatment switching of Ions
R&D with other Ions
IMRT PBS Raster scanning, Adjustable beam size 5 – 20 mm
Easy and flexible adaptation of treatment plan to tumor geometry
One room setup
Compact size, low civil engineering cost
Modular build up, fast installation and easy logistics
Less secondary radiation and shielding requirements
Compact One-Room solution
Patent pending
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One-Room – front view
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One-Room – back view
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SC magnets advantage: smaller size, lower weight, lower power
Added complexity for cryo cooling – on a rotating structure
Ramping speed:
Does this impact the operation & the number of patients per year ?
Reliability:
Failure rate for room-temp magnets is very low,
Failure rate for mature SC magnets is very low, what about new type SC ?
Recovery from quench can be very long
Compare three cases: HIMAC SC, HIT RT, Danfysik RT
Carbon Gantry: SC vs RT
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10 SC magnets
90º magnet = 4x 22.5º
Power consumption from cryopumps (always on)
SC Carbon gantry (HIMAC)
HIMAC
Magnets for 90 degree angle 4x 22.5º
Weight 90 degree magnets 27 t
Total weight magnets 41 t
Gantry structure, including magnets 300 t
Field (T) 2.4 - 2.9
Scanning area (mm) 200x200
Source to axis distance >30
Size of gantry 19 x 12 m
Power consumption estimate (MW) 0,3
Energy estimate (GWh/y) 2,6
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90º magnet one single device
Power consumption from electromagnets, only on during treatment
Room temp C gantry (HIT)
HIMAC HIT
Magnets for 90 degree angle 4x 22.5º 1x 90º
Weight 90 degree magnets 27 t 90 t
Total weight magnets 41 t 138 t
Gantry structure, including magnets 300 t 600 t
Field (T) 2.4 - 2.9 1.8
Scanning area (mm) 200x200 200x200
Source to axis distance >30 >30
Size of gantry 19 x 12 m 25 x 13 m
Power consumption estimate (MW) 0,3 0,8
Energy estimate (GWh/y) 2,6 2,1
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Similar to HIT, 90º magnet split into three 30º magnets
Scanning magnet before the last 30º magnet
Reduction of weight of the magnets and the gantry structure
Room temp C gantry (Danfysik)
Scanning magnets
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Photograph of installed vertical beam-line
Room temp gantry magnets
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Danfysik vs HIT:
Smaller weight
Similar size
Lower power
Comparison C gantries
HIMAC HIT Danfysik
Magnets for 90 degree angle 4x 22.5º 1x 90º 3x 30º
Weight 90 degree magnets 27 t 90 t 48 t
Total weight magnets 41 t 138 t 81 t
Gantry structure, including magnets 300 t 600 t 450 t
Field (T) 2.4 - 2.9 1.8 1.8
Scanning area (mm) 200x200 200x200 200x200
Source to axis distance >30 >30 4.5; >30
Size of gantry 19 x 12 m 25 x 13 m 25 x 14 m
Power consumption estimate (MW) 0,3 0,8 0,7
Energy estimate (GWh/y) 2,6 2,1 1,9
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Gantry used for flexibility, robust treatment planning, avoid OAR exposure
Several gantry geometries:
Isocentric, Riesenrad, multi-room, multi-angle
Superconducting or room-temparture for carbon ion PT
Alternatives to gantries:
Fixed beams, 0 degree, 45 degree and 90 degree
Rotate patient, rotate chair
Superconducting magnets: stronger field, smaller size and lower weight
Several compact gantry solutions for proton (& helium)
Conclusion