Prompt gamma measurements for the
verification of dose deposition in proton therapy
Jong-Won Kim
National Cancer Center, Korea
H. Kubo, T. Tanimori
Department of Physics, Kyoto University, Japan
Two Proton Beam Facilities for Therapy and
Research
Ion Beam Facilities in Korea
1. Proton therapy facility at National Caner Center
2. Neutron therapy facility at Korea Cancer Center Hospital
•2002
2002 July: Contract with IBA
•2003
2003 Jun: Start building construct
•2005
2005 Feb: Start iinstallation
nstallation
•2006
2006 Dec: Accept 1st gantry room
•2007
2007 Mar 19: Treat the first patient
Necessity of Proton Range Localization
Contents
1. Gamma production by proton beam
2. Prompt gamma detection techniques
2.1 A collimation method
2.2 A pinhole camera method
2.3 Compton camera method
3. Monte Carlo simulation studies for prompt
gamma imaging
4. Concluding remarks
X-ray
Proton
•
•
Clinical data show significant decrease
in tumor control (>5%) when tumor
dose decreased by 4-5%.
Therefore “ significant” portion of CTV
cannot fall outside high dose region
more than once in fractionated course
of radiation
L. Vehey UCSF
Uncertainty in range calculation based on XX-ray CT
1. Gamma production by proton bombardment on
tissue nuclei
Gamma lines by proton interaction with organic nuclei
E (MeV)
Transition
0.718
10 ∗0.718
0.937
1.022
Photo of
irradiated
PMMA sample
E. Testa et al., Monitoring the Bragg peak
location of 73 MeV/u carbon ions by
means of prompt γ-ray measurements,
Applied Phys. Lett. (2008)
B
18 ∗ 0.937
F
B
10 ∗1.740
Reaction
g.s.
g.s.
10 ∗0.718
B
1.042
1.635
2.000
2.124
2.313
18 ∗1.042
2.742
3.736
4.438
16
4.444
11 ∗4.445
B
g.s.
5.105
14
N∗5.106
g.s.
5.180
6.129
6.916
7.115
15.10
F
N∗3.948
C∗2.000
11 ∗2.125
B
14 ∗2.313
N
14
11
40
12
g.s.
14 ∗ 2.313
N
g.s.
g.s.
g.s.
O∗8.872 16O∗6.130
Ca∗3.736 g.s.
C∗4.439 g.s.
15
O5.181 g.s.
O∗6.130 g.s.
16 ∗6.917
O
g.s.
16 ∗7.117
O
g.s.
12 ∗15.11
C
g.s.
16
12
C(p,x)10B∗
12
C(p,x)10C(ε)10B∗
16
O(p,x)10B∗
16
O(3He,p)18F*
12
C(p,x)10B∗
16
O(p,x)10B∗
16
O(3He,p)18F*
14
N(p,p*)14N*
12
C(p,x)11C∗
12
C(p,x)11B∗
14
N(p,p*)14N∗
16
O(p,x)14N∗
16
O(p,p*)16O∗
40
Ca(p,p*)40Ca∗
12
C(p,p*)12C∗
14
N(p,x)12C∗
16
O(p,x)12C∗
12
C(p,2p)11B∗
14
N(p,x)11B∗
14
N(p,p*)14N∗
16
O(p,x)14N∗
16
O(p,x)15O∗
16
O(p,p*)16O∗
16
O(p,p*)16O∗
16
O(p,p*)16O∗
12
C(p,p*)12C∗
Mean Life (s)
1.0 × 10−9
27.8
1.0 × 10−9
6.8 × 10−11
7.5 × 10−15
7.5 × 10−15
2.6 × 10−15
6.9 × 10−15
1.0 × 10−14
5.5 × 10−15
9.8 × 10−14
9.8 × 10−14
1.8 × 10−13
2.9 × 10−11
6.1 × 10−14
6.1 × 10−14
6.1 × 10−14
5.6 × 10−19
5.6 × 10−19
6.3 × 10−12
6.3 × 10−12
< 4.9 × 10−14
2.7 × 10−11
6.8 × 10−15
1.2 × 10−14
1.5 × 10−17
B. Kozlovsky et al., Astrophysics J., Suppl. Ser. 141 (2002)
First suggestion of utilizing prompt gamma for range
verification
F. Stichelbaut, Y. Jongen,
Verification of the Proton Beam Position
in the Patient by the Detection of Prompt
γ-Rays Emission, PTCOG-39, 2003
Ep= 214 MeV (range=28.5 cm)
Phantom size: 40 x 20 x 20 cm3
GEANT 3.21 with hadronic model
of Fluka
Distributions with angular cuts (± Δθ)
Secondary γ : photons from n-capture and
inelastic scattering
PET method to monitor the ranges of hadron
therapy beams
First suggestion (?):
G.W. Bennett et al., Science 200
(1978)
Proton: 250 MeV
D. Litzenberg et al., Med Phys. (1999)
Institute of Nuclear and Hadron Physics , GSI, Germany
Many publications for HI cases: e.g) F. Sommerer et al.,
Phys. Med. Biol. 54 (2009)
2. Prompt gamma detection techniques
Measurement at the experimental room of the NCC
2.1 Prompt gamma measurement using a multi-layer
collimator
CsI(Tl)
Comparisons of the depth dose distributions measured by the ionization
chamber to the PGS (Prompt gamma scanner) measurements at three
different proton energies of 100, 150, 200 MeV’s.
MCNPX (Ver. 2.5.0.e)
FLUKA (Ver. 2003)
4 mm x 30 mm
Angular span: 90±α
G. Seo, MS. thesis, 2006
C. Min, C. Kim, M. Youn, J. Kim, App. Phys. Letts. 89 (2006)
Analysis of prompt gamma measurements
Effects of with and without paraffin shielding
CsI(Tl)
2 MeV
The gamma-count distributions vs. depth
with different minimum gamma energies
4 MeV
6 MeV
The gamma
gamma--energy spectrum
measured at three different
locations adjacent to the Bragg peak
at the proton energy of 100 MeV.
(The inset is the energy calibration
for the MCA..)
The gamma-count distributions versus
depth with and without paraffin shielding
plates surrounding the outside of the PGS
Measurements at the therapy beam line of the NCC
Prompt gamma measurement for an ATOM
phantom using mono-energetic beams
Relative prompt gammas (normalized)
1.05
1.00
70 mm
90 mm
0.95
0.90
0.85
0.80
0.75
0.70
0.65
0
Set-up at the horizontal
fixed beam line of the NCC
20
40
60
80
100
120
140
Depth in ATOM phantom (mm)
ATOM phantom
Bone density: 1.6 g/cc
Composition: C(37%), O(35%), Ca(15%), H(4.8%), P(2.9%), Mg(6.2%)
Range: 7.0 cm
A single scattering, field radius=2 cm
2.2 A pinhole Camera Method
Measurement results with a pinhole camera
Prompt gamma distributions by the
pinhole camera calculated with GEANT
Prompt gamma measured at a proton
beam energy of 40-42 MeV
Measurement with 50-MeV proton beam using
MC50 cyclotron at Korea Cancer Center Hospital
Shielding thickness estimation for a 50 MeV proton beam with GEANT3
D. Kim, H. Yim, J. Kim,
submitted to J. of Korean
Physical Soc. June, 2009
Peak variation: 0.5 mm / MeV
GEANT simulation for electron-tracking Compton
camera
2.3 Compton camera method
2) Compton cameras of two types
1) SPECT
Compton camera measurement simulation of 90° emitted gammas
solid or gas
Collimator
Photon Energy
E: ~ < 300 keV
Compton camera
E: 200 ~ 2000 keV
B. Kang, J. Kim, IEEE Nucl. Sci. 2009
Compton camera measurements of prompt
gammas by a group of Kyoto University
GEANT simulation results for electron-tracking
Compton camera
Reconstruction resolution
MeV γ-rays
2 mm
PCB detector
Compton
scattering
Cathode
Anode
eSubstrate
’
Pixellated CsI(Tl)
2.8 mm
16x16 multianode
photomultiplier
5 cm
Estimated resolution
of reconstruction
relative to the
location of gamma
emission.
Reconstruction resolution vs. detector performance
cos φ = me c 2 (
cos α = 1 −
1
1
−
), E o = E r ' + E e
Er' Eo
me c 2
Eγ ,
Ee
E e + 2m e c 2
Water phantom
20x20x40 cm3
Size
TPC
Size
5x3x5(h) cm3
Gas
Ar:C2H6=90:10
Electron drift velocity
No of anode/cathode
channels
4 cm/ms
Pitch of electrode
2 mm
electron dE/E
25/15
30%
CsI (Tl)
Pixel size
2 x 2 mm2
No of channels
16x20
gamma dE/E
7%
Measurements of prompt gamma
spectra and background neutrons at
RCNP of Osaka University (July, 2008)
Prompt gamma image measurement
at the proton therapy center of
Tsukuba University (Jan. 2009)
Set-up for prompt gamma image measurement with
Compton camera at Tsukuba proton therapy center
GSO Energy Spectrum
RCNP experiment
Tsukuba experiment
Prompt gamma images analyzed for different
energy ranges
:Location of Bragg peak
Counts (a. u.)
[cm]
Energy range:447-581keV (± 2xFWHM)
proton
Monte Carlo simulation of prompt gamma imaging for a
200 MeV proton beam
(1σ
σ): 11 mm
Beam size (1
Avg. beam current: 30 pA
Beam time: 14 hours
~100 Gy
Iteration
39cm
image
fusion
109 events
[cm]
proton
Counts (a. u.)
254 events
Energy range:600-900keV (± 2xFWHM)
[cm]
proton
Counts (a. u.)
[cm]
Energy range:268-443keV (± 2xFWHM)
98 events
[cm]
[cm]
By K. Ueno and S. Kurosawa
of Kyoto University
Passage to improve detection efficiency of
electron-tracking Compton camera
3. MC simulation studies for prompt gamma imaging
Monte Carlo simulation study on a photodiode array detector
Current efficiency of electron tracking type: 10-5 with Gas
volume of 10 x 10 x 10 cm3
10-3
(Efficiency by solid scatter: 10-2)
• Use of different gas: Ar
CF4
• Increase gas pressure: 1 atm
2 atm
• Improvement of 3D tracking algorithm of Compton scattered
election
MCNPX, LA150 and
ENDF/BVI libraries
Monte Carlo calculations on prompt gamma
emission from biological tissues
MCNPX calculations at MD Anderson Cancer Center
C. Min et al., J. of Korean Phys. Soc. (2008)
Concluding remarks
1. Prompt gamma appears to be a promising modality
of proton range verification considering its capability
of on-time monitoring with therapy and good
correlation with proton dose distribution.
2. Prompt gamma measurement using collimation
system can be a viable tool for the verification of
proton range especially for the scanning beams.
J. Polf et al., Prompt gamma emission
from biological tissues during proton
irradiation: a preliminary study, Phys.
Med. Biol. 54 (2009)
3. Electron-tracking Compton camera can be a tool for
prompt gamma imaging with improvement in
detection efficiency to its full potential.
Acknowledgements
Seoul National University, Department of Physics
D. Kim, Ph.D student
Kyoto University, Department of Physics
S. Kurosawa, Ph.D student
K. Ueno, Ph.D student
Thank you for your attention !