Beam production techniques for hadron therapy Documents... · Beam production techniques . for . hadron therapy. ... Amaldi et al, Nucl Instr Meth A 521(2004) 512 ; ... 2 2 0. 1.

Beam delivery techniques for hadron therapy Marco Schippers, PSI Winterschool, Jan 2010 1

Beam production techniques for

hadron therapy

Marco Schippers


Contents

•

Facility configuration•

Dose delivery techniques

•

Accelerators•

New accelerator developments


accelerator

fix horgantry gantry

(energy selection) beam transport

Facility configuration

modules

•

1 accelerator

•

3-5 treatment rooms (incl

2-4 gantries)

•

Beam to 1 room at the time


IBA

PSI ACCEL/Varian cyclotron

Tsukuba

Proton therapy facility: modules

accelerator

energy selection

beam transport

gantry / fixed hor. line


accelerator

fix horgantry gantry

(energy selection) beam transport

Proton therapy facility: modules

However, NOT independent….

Beam delivery => accelerator and energy selection


Dose deliverytechniques

http://www.medport.de/lexikon/index.php/Bild:Schneekanone.jpg


fast degrader (PSI)

Methods:1)

Vary energy

in accelerator (synchrotron)

2)

Slow down

from fixed to desired energy

-

degrade in beam line (PSI)

-

modulate just before patient (in “nozzle”)

250 MeV

protons250 MeV

protonsSpread-out Bragg peak

Considerations:how fast ? how accurate ? effect on beam ?

Dose delivery techniques: Depth


Dose delivery techniques: Width

transversal spread:

scattering

scanning(protons only)

(all hadrons)

CollimatorScatter syst.


Proton therapy with a scattered beam

Scatter

foils

Range

compensation

Collimator

Requirements for accelerator:-

stable beam position

-

enough intensity

-

enough energy

Energy modulation


allows fast target repainting: 15-30 scans / 2 min.

Pencil beam scanning

0 time (ms) 10

inte

nsity

Continuous scanning

kHz-Intensity modulation Requirements for accelerator:-


-

continuous and stable beam

-

fast adjustable beam intensity

-

fast adjustable beam energy

Spot scanning: step&shoot Requirements for accelerator:-



Accelerators


Accelerator

Source++++

250 MeV+

+ _250 000 000

Volt


Protons in use, ∅3.5-5 m

Present accelerator choice

e.g.:

Loma Linda

Houston

Tsukuba

3.5 m

e.g:

Boston

Florida

Seoul

Wanjie

PSI

München

Orsay

in use, ∅8-10 m

Carbon ions

in design, ∅6 m

cyclotron synchrotron

in use, ∅25 m


Synchrotron (1945)

Ring:

• acceleration to desired E

• storing of the beam

Magnet to select ion source

Injection in ring at 7 MeV/nucl

2 linear accelerators in series

Ion sources for different particles

Extraction into beam line

~50

m

(DKFZ, GSI,

Siemens)+

+

+

++


Beam extraction from synchrotron

( Hitachi )

RF-driven extraction


Time 0.5-1 sec

“spill”

time •

fill ring with ~109 particles

•

accelerate to desired energy•

extract slowly during 1-10 sec

•

decelerate and dump unused particles

Bea

m in

tens

itySynchrotron beam structure: noisy & spills

1-10 sec

σ=15%


oscillating high voltageon “Dee”

electrode

Extractor:-HVVdee

~

RF-Electrodes: 2 “Dees”

At each

electrode

border:Energy gain

ΔE=Vdee

Ion source

Cyclotron (1930)

Ernest Lawrence

(1901-1958)Magnet


Extractor

Vdee

~+

Cyclotron

Circular orbits:Centripetal force = Magnetic force

=>

=> Tcircle

independent from orbit radius r

Bqvr

mv=

2

BqmTcircle.2π

=

m

= mass

v

= speed

r

= orbit radius

B

= magnetic field

q

= charge

r


230 MeV

cyclotron (IBA,1996)PSI Injector 1, 72 MeV, 1970

Cyclotron12 MeV

cyclotron (UC, 1940)80 keV

protons

10 cm

Dee

extractor

1930


superconducting coils => 2.4 -

3.8 T

Proton source

4 RF-cavities ~100 kV on 4 Dees

Closed

He system4 x 1.5 W @4K

300 kW90 tons

3.4 m

1.4 m250 MeV proton

cyclotron

(ACCEL/Varian)

ACCEL


pole

pole

Internal

proton

source

~5 cm

anodecathode

at -HV

anodecathode

at -HV

-80 kVDee

1

+


Intensity

controlMax. intensity

set

by:

Ion source

+ slits

Deflector plate:sets requested

intensity

- within 50 µs - 5% accuracy

currently only possible with a cyclotron


Extraction from cyclotron

Electrostaticextraction elements

80%

(ACCEL / Varian)

Low radioactivity


Kicker

Beam-energy adjustment

Degrader

unitAll following magnets: 1% field change in 50 ms

Steerer

Q Q Q

Carbon wedge degrader238-70 MeV 5 mm ΔRange

in 50 ms

Dipole magnets in beam line:1.1 T190 A100 A/s (1-1.4 H)


Energy scanning, Estep

~5 mm range

in water.

Degrader

50 ms



~5 mm range

in water.

Degrader

Current

in Dipole

50 ms



~5 mm range

in water.

Degrader

Current

in Dipole

Beam

energy

error

50 ms


cyclotron

synchrotronCarbon ions

in development

easy

Change particle

in development

easy

Time structure

continuous dead time

Fast E-scanning

degrader

next spill

Activation degrader to be shielded

no

Intensity

“any”, adjustable

limited, per spill

Intensity stability

3-5%

15-20%

Size ∅

3.5 (p)-6 m (C)

6(p)-25 m (C)

Scattering

ok

ok

Spot scanning

ok

ok

Fast continuous scanning

ok

difficult

some differences…


The Holy Grail for proton therapy:

protons

MeV one small (cheap) accelerator

per treatment room


New accelerator types….

http://www.theskistop.com/perfect-ride/equipment/z10.html


http://www.theskistop.com/perfect-ride/equipment/z-oversize.html

http://www.theskistop.com/perfect-ride/equipment/attraxion-vi.html

http://www.theskistop.com/perfect-ride/equipment/attraxion-i.html



http://www.theskistop.com/perfect-ride/equipment/phantom-sc95.html

http://www.theskistop.com/perfect-ride/equipment/phantom-sc80.html

http://www.theskistop.com/perfect-ride/equipment/classic-cx80.html

http://www.theskistop.com/perfect-ride/equipment/classic-cs70.html

http://www.theskistop.com/perfect-ride/equipment/attraxion-xi.html

http://www.theskistop.com/perfect-ride/equipment/voodoo-sc95.html

http://www.theskistop.com/perfect-ride/equipment/voodoo-sc80.html


Small cyclotron on a gantryH. Blosser, NSCL (~1990):cyclotron

for

neutron

therapy;

30 MeV p, mounted

on a gantryUsed

in Harper Hospital, Detroit

Proposal of H.Blosser

et al.,1989:-250 MeV-52 tons, on gantry-B(0)=5.5 Tesla


—No beam extracted yet (oct

2009)—Many uncertainties on performance and reliability

( @ limit

of current

technology )—No beam

analysis

—Neutrons ?

Still River

Synchro-Cyclotron8-10 T Synchro-cyclotron on a gantry


Carbon-ion cyclotrons

25 mProton

(250 MeV)

2.43 Tm

Helium 2+ (250 MeV/nucl)

4.86 Tm

Carbon 6+ ( 450 MeV/nucl

)

6.83 Tm

Range in water =38 cm Range =33 cm

⇒

Cyclotron

radius

of is

2.8

x R proton

cyclotron

⇒

~ 2.82

= 8 x more

iron => 700-800 tons


700 tonsSC coils Ø 7 m

Carbon

ions

protons

Int. Conf. Cyclotron and appl, Tokyo 2004

IBAArchade

project

Accelerator choice


250 MeV/nucl.H2

+ α

C6+

450 MeV/nucl. C6+

250 MeV/nucl.H2

+ α

C6+

450 MeV/nucl. C6+Start with protons AND•

α

+ (up to 12.5 cm:) Carbon

•

Second step: also 450 MeV/nucl

Carbon

PSI design for 2-step approach

Accelerator choice


Proof of principle FFAG accelerator

at KEK in Japan. (Muri

et al)

Fixed Field Alternating Gradient accelerator (FFAG)

Advantage:

Fast energy

change

in accelerator

Disadvantages:

Heavy (100-200 tons)

Injector

cyclotron

needed

Pulsed

Receipe:1) inject

into

ring

2) RF until

E reached3) extract.

Accelerator choice


High gradient (100 MeV/m) Linac

(dielectric wall)

Proton-TomotherapyCaporaso

et al, Nucl

Instr

Meth B 261 (2007) 777

Dielectric material

electrode, pulsed

High Voltage

2 ns pulses

with 100mA protons

at 10 Hz

needed: reached:100 MV/m

20 MV/m

2.5 m 2 cm —

Pulsed beam

—

Low duty cycle

—

dose accuracy

?

New accelerator types

(2009)


C.M. Ma, Laser Physics, 2006, Vol. 16, No. 4, pp. 639

Lase

r bea

m lin

eprotons

Laser driven proton accelerator

—

Pulsed beam

—

Low duty cycle

—

Neutrons



Amaldi

et al, Nucl

Instr

Meth A 521(2004) 512

Cyclotron driven linac



Plasma wake field accelerator

Blumenfeld, et al. Nature 445, 741–744 (2007).

Nature

449 133-135 (2007)

Accelerator choice

(electron) energy doubler


Now Mañana

Time until useable

Accelerator choice (protons)C

urre

ntU

seab

ility

=> Q

ualit

ycyclotron

synchrotron

Synchro-cyclotron

FFAGDielectr. wall

linacs

cyclotron driven linac

lasersPlasma

wake field


•

Time structure: continuous/pulsed

•

Intensity (stability)

•

Beam position stability

•

(fast) E-scanning possible?

•

Control; area/mode

changes

•

Activation of components

•

Reliability, service friendliness

•

Control

system: modularity

•

Size, weight, power

Summary of accelerator specs


Concerns on new accelerators:1) at least the same quality

as we have now?

and, if yes:

2) advantages

(costs?) and when available?

Concerns on future developments:Industry is now “producing”

particle therapy.

=>however: reluctance to invest

in next steps

=>cheap

particles could be disadvantageous

conclusions


Pick your choice how to accelerate….



24 h after beam off, April 2008(extracted beam integral: 200 μA.h)

on pole: 400 -

500

μSv/h

mid plane:

250 -

400

μSv/h

10 cm unshielded degr.

500-1000 μSv/hnext to shielded degrader

10-20

μSv/h

mid

plane,

open

cap

>80% extraction

eff.=> Low dose to staff


BqmTcircle.2π

=

However, when v c:

e.g:

250 MeV

p: v/c=0.61 =>

m=1.27m0

=> Tcircle

increases with radius => particles lose pace with RF.

Remedy: increase B

with radius

220

1 cvmm−

=

Relativity in high-E cyclotrons

=>

Tcircle

constant for all radii


Conc

eptu

al de

sign

synchro- cyclotron

Energy Selection System

Gantry with integrated accelerator and ESS

8-10 T field:

250 MeV

synchro-cyclotron

⇒

pulsed beam (~1 kHz)

⇒

low duty cycle



D.Trbojevic

et al., Proc

PAC07

FFAG optics for a Gantry