PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

Proton therapyre

lativ

e do

se

depth

g p

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 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico 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

WHM

(mm

)

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 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico 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 104

X[mm]

Coun

ts

Edge profile

5mm10mm15mm20mm25mm30mm35mm40mm45mm50mm

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

slit collimator opening: 6mm

Proton range measurements:the experimental set-up

p beam

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

PMMA target

protonbeamslit collimator

HICAMcamera

g-rays

electronics

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

0 2 4 6 8 10 12 14 16

102

103

Energy [MeV]

Coun

ts

Measured energy spectrum

LYSObackground

3-7MeVrangeused in reconstruction

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico 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]

Coun

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]

Coun

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]

Coun

tsProfile

cameraposition

- 4cm

cameracentered

cameraposition

+ 4cm

Measured profiles

subtraction

simulation

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico 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

tons

Fitted edges

+10mm0mm-1mm-2mm-3mm-5mm-10mm

(preliminary analysis)

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

-10 -5 0 5 10-0.5

0

0.5

1

1.5

2

Theoretical Shift[mm]

Accu

racy

[mm

]

-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 Po

sitio

n[m

m]

TheoreticalMeasured

Shift accuracy

20 25 30 35 40

2.8

3

3.2

3.4

3.6

3.8

4

4.2

4.4x 10-8

Width [mm]

Fitti

ngs

1mm Step

X10 X0 X-10

reference value

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

Precision

reference position

reference value

fitting error

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico 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]

Prec

isio

n - 6

8% c

onfid

ence

inte

rval

[mm

]

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

0 10 20 30 40 50 60 70 80 90 1000

0.5

1

1.5

2

2.5

Statistics[%]

Prec

isio

n - 6

8% c

onfid

ence

inte

rval

[mm

]

7·1010 protons

Precision vs. statistics

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico 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

tons

Fitted edges

+10mm0mm-1mm-2mm-3mm-5mm-10mm

each acquisition:• 2min.• 1.7·1010 protons

(preliminary analysis)

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico di Milano, Italy

-10 -5 0 5 10-0.5

0

0.5

1

1.5

2

2.5

3

Theoretical Shift[mm]

Accu

racy

[mm

]

-10 -5 0 5 10-10

-8

-6

-4

-2

0

2

4

6

8

10

Theoretical Shift[mm]

Mea

sure

d Po

sitio

n[m

m]

TheoreticalMeasured

-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]

Prec

isio

n - 6

8% c

onfid

ence

inte

rval

[mm

]

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

Statistics[%]

Prec

isio

n - 6

8% c

onfid

ence

inte

rval

[mm

]

1.7·1010 protons

PSD9, Aberystwyth, UK, 15 Sept. 2011 carlo.fiorini@polimi.itPolitecnico 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 carlo.fiorini@polimi.itPolitecnico di Milano, Italy