psd9, aberystwyth, uk, 15 sept. 2011 [email protected] politecnico di milano, italy...
TRANSCRIPT
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
Development of a camera for imaging of prompt gamma rays in measurements of proton beam range
P.Busca1,2, C.Fiorini1,2, R.Peloso1,2, M.Basilavecchia3, T.Frizzi3, D. Prieels4,
J. Smeets5*, F. Stichelbaut4, A. Benilov4, F. Roellinghoff4
1Politecnico di Milano and INFN, Milano, Italy2XGLab, Milano, Italy4 Ion Beam Applications S.A., Louvain-la-Neuve, Belgium 5 Department of Nuclear Metrology, Université Libre de Bruxelles, Brussels, Belgium
• Work supported in part by the European Union Seventh Framework Program (FP7/2007-2013) under grant agreements nos. 241851 (ENVISION) and 264552 (ENTERVISION).
• HICAM gamma detector developed within the EC contract n.LSHC-CT-2006-037737.• *supported by the Belgian FNRS (aspirant)
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
Proton therapyre
lativ
e d
ose
depth
gp
Bragg-peak• particle (proton) therapy has a growing role in cancer treatment. • possibility to release the maximum of the dose in the target site, limiting the dose to normal tissue
• the measurement of the proton beam range in the target is very important: real range of proton beams in patients may contain uncertainties of up to 10-15 mm (uncertainties on tissue composition, density, organ motions, patient positioning, etc).
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
One method to measure proton beam range is based on the measurement of prompt gamma rays (energies up to 10MeV) emitted by excited nuclei during proton irradiation.
(F. Stichelbaut, Y. Jongen, 39th Meet. of the Particle Therapy Co-Operative Group, San Francisco, October 2003)
Monte Carlo simulation
p beam
target
p beam
promptgs
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
Practical concept of a prompt gamma camera which allows checking in real-time the range of a single pencil beam with a ‘mm’ accuracy
(D. Prieels, J. Smeets, F. Stichelbaut, A. Benilov, J.C. Dehaes, A. Dubus, F. Roellinghoff, 50th Meet. of the Particle Therapy Co-Operative Group (Philadelphia), May 2011
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
HICAM:HIgh resolution gamma CAMera
scintillator
matrix of photodetectors
cooling systems
bias and read-out electronic
Rigid-Flex Printed Circuit
scintillator
matrix of photodetectors
cooling systems
bias and read-out electronic
Rigid-Flex Printed Circuit
scintillator
matrix of photodetectors
cooling systems
bias and read-out electronic
Rigid-Flex Printed Circuit
- CsI(Tl) scintillator- SDDs photodetectors- 5x6cm2 and 10x12cm2 formats- intrinsic resolution~1mm- compactness
Anger camera principle
scintillation entering side
drift
Silicon Drift Detectors
Research project from European Community(www.hi-cam.org)
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
The HICAM gamma camera development(R.Peloso, et al., “The HICAM Gamma Camera”, Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE)
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
0 20 40 60 80 100
Distance (mm)
Reso
lutio
n, F
WH
M (m
m)
Imaging performances with 99Tc (140keV)
LEUHR parallel hole collimator
intrinsic resolution= 0.8mm
10,8 cm
8,7 cm
corrected for linearity and uniformity
Hole Ø=1mmPitch=3mm
Grid
99Tc
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
50 m
m50
mm
Applications of the HICAM gamma camera(P.Busca, et al., “Applications of the HICAM Gamma Camera”, Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE)
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
• 1cm thick LYSO scintillator (h~37%@1MeV, ~22%@5MeV)• light collection purposely limited (i.e. all
absorbing surfaces) to match readout ASIC dynamic range (designed for 200keV)
( ~ 5e-/keV, vs. 30ph./keV from LYSO)
Modification of the 5x6cm2 HICAM gamma camerafor high-energy (1-10MeV)imaging
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
Camera FOV
source lead block
lead block thickness=3cm
Source: 60Co (1.17MeV, 1.33MeV)
Area considered for profile calculation
1D profile calculation along X:integration on the Y direction(1mm bin)
Laboratory characterization of the camera
Y
X
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
10 15 20 25 30 35 40 45 50 551.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2x 10
4
X[mm]
Co
un
ts
Edge profile
5mm
10mm15mm
20mm
25mm
30mm
35mm
40mm45mm
50mm
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
slit collimator opening: 6mm
Proton range measurements:the experimental set-up
p beam
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
PMMA target
protonbeamslit collimator
HICAMcamera
g-rays
electronics
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
0 2 4 6 8 10 12 14 16
102
103
Energy [MeV]
Co
un
ts
Measured energy spectrum
LYSObackground
3-7MeVrangeused in reconstruction
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
Beam energy: 160MeV
0 20 40 60 80 100 120 1400
200
400
600
800
1000
1200
1400
1600
1800
Width [mm]
Co
un
ts
Neutron
slits closed (neutrons + uncorrelated photons)
0 20 40 60 80 100 120 1400
100
200
300
400
500
600
700
800
900
Width [mm]
Co
un
tsSubtraction
central profileis fitted and monitoredwhile moving thetarget (and the Bragg-peak)
0 20 40 60 80 100 120 1400
500
1000
1500
2000
2500
Width [mm]
Co
un
tsProfile
cameraposition
- 4cm
cameracentered
cameraposition
+ 4cm
Measured profiles
subtraction
simulation
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
100MeV protons
each acquisition:• 5min.• 7·1010 protons
-10mm
+10mm
10 15 20 25 30 35 40 45 502
2.5
3
3.5
4
x 10-8
X[mm]
Gam
mas
/Pro
ton
s
Fitted edges
+10mm
0mm
-1mm
-2mm-3mm
-5mm
-10mm
(preliminary analysis)
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
-10 -5 0 5 10-0.5
0
0.5
1
1.5
2
Theoretical Shift[mm]
Acc
ura
cy[m
m]
-10 -8 -6 -4 -2 0 2 4 6 8 10
-10
-8
-6
-4
-2
0
2
4
6
8
10
Theoretical Shift[mm]
Mea
sure
d P
osi
tio
n[m
m]
Theoretical
Measured
Shift accuracy
20 25 30 35 40
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
x 10-8
Width [mm]
Fit
tin
gs
1mm Step
X10 X0 X-10
reference value
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
Precision
reference position
reference value
fitting error
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
-10 -8 -6 -4 -2 0 2 4 6 8 100.6
0.7
0.8
0.9
1
1.1
1.2
1.3
Reference Position[mm]
Pre
cisi
on
- 6
8% c
on
fid
ence
in
terv
al[m
m]
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
0 10 20 30 40 50 60 70 80 90 1000
0.5
1
1.5
2
2.5
Statistics[%]
Pre
cisi
on
- 6
8% c
on
fid
ence
in
terv
al[m
m]
7·1010 protons
Precision vs. statistics
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
160MeV protons
10 15 20 25 30 35 40 45 50
4.5
5
5.5
6
6.5
x 10-8
X[mm]
Gam
mas
\Pro
ton
s
Fitted edges
+10mm0mm
-1mm
-2mm
-3mm
-5mm-10mm
each acquisition:• 2min.• 1.7·1010 protons
(preliminary analysis)
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
-10 -5 0 5 10-0.5
0
0.5
1
1.5
2
2.5
3
Theoretical Shift[mm]
Acc
ura
cy[m
m]
-10 -5 0 5 10
-10
-8
-6
-4
-2
0
2
4
6
8
10
Theoretical Shift[mm]
Mea
sure
d P
osi
tio
n[m
m]
Theoretical
Measured
-1 0 1 2 3 4 5 6 7 8 9 101.5
1.6
1.7
1.8
1.9
2
2.1
Reference Position[mm]
Pre
cisi
on
- 6
8% c
on
fid
ence
in
terv
al[m
m]
0 10 20 30 40 50 60 70 80 90 1000
5
10
15
Statistics[%]
Pre
cis
ion
- 6
8%
co
nfi
den
ce i
nte
rval[
mm
]
1.7·1010 protons
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy
Conclusions
• Measurements of prompt gammas correlated to proton range were successfully made using the HICAM gamma camera
• Although not optimized for 1-10MeV energy range (low efficiency, low scintillator light collection), satisfactory accuracy and precision (in the ‘mm’ range) were first measured
Future work
• Further data analysis also to correlate results to dose expected in patient treatment.
• Measurements to be repeated also with other protons energies (230MeV).
• Gamma camera to be modified/redesigned to improve efficiency and speed
PSD9, Aberystwyth, UK, 15 Sept. 2011 [email protected] di Milano, Italy