Introduction to Gantries and Comparison of Gantry Design

Marco Pullia, CNAO & Frank Ebskamp, Danfysik

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

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

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

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

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)

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

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

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

Conventional RT

Proton GantryBr < 2.4 Tm

Carbon Ion GantryBr < 6.6 Tm

Deep pit under the patient

Size and magnetic rigidity

Proton gantries

Mitsubishi

Hitachi

IBA

Proton gantry geometries

(Adapted from a slide of J. Flanz)

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

Carbon Gantry

The HIT Gantry:the only clinical C Gantry

L = 25 m x f = 13 m,

600 t rotating mass

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)

NIRS Gantry

Progressively increasing aperture

Combined function,Superconducting magnets

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

Chair

Alternatives

Hyogo

CNAO(for eye treatment)

Cradle couch at HIMAC

Alternatives …

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

Planar system

Proposed by M. Kats

Circular exit face withcenter on beam entry position. Exit edge angleequals half bending angle.

Mobile isocenter gantry

AVO / TERA: Linac Image Guided Hadron Technology

Low cost, compact, modular

LIGHT systems planned for UK and China

LIGHT: linear PT Gantry system

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

One-Room – front view

One-Room – back view

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

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

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

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

Photograph of installed vertical beam-line

Room temp gantry magnets

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

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