PROTON BEAM

DOSIMETRY

Lenka Goceliaková

International Summer Student Practice at the Joint Institute for Nuclear Research

6 – 27 July 2014, Dubna

PROTON BEAM DOSIMETRY

Project participant:

Lenka Goceliaková

University of Pavol Jozef Šafárik, Faculty of Science,

Košice, Slovakia

Supervisor:

Dr. S.V. Shvidky

Medico – Technical Complex,

Dzhelepov Laboratory of Nuclear Problems,

JINR, Dubna

AIM OF THE PROJECT

• To verify the correspondence of the dose

distribution in case of therapeutical proton

beam, using film dosimetry and simulations in

the 3D Treatment Planning System (TPS)

• To compare the dose distribution obtained

using EBT films and the 3D TPS

• To compare EBT2 & new EBT3 films

Why do we need the dosimetry?

• To verify the accuracy of a planning system

calculation algorithm and to determine the

distal dose for the volume.

Proton beam dosimetry

• Measurements of the radiation dose

0,0001 Gy – 3 Gy

Properties of the Gafchromic films:

•EBT2, EBT3

•self developing dosimetry films

When the active component is exposed to ionizing

radiation, it reacts and forms a green colored

polymer.

Materials and Methods

• Irradiation EBT2 & EBT3 calibrate films(picture with the small pieces)

• Irradiation EBT2 & EBT3 films

• Scanning of films

• Drawing of calibration curves

• Calculation of the matrices for all films

• Comparison of the dose distribution using EBT films dosimetry and the 3D TPS

• Gamma – index calculation

Irradiation Method • The films were irradiated individually with protons in a

water tank;

• The proton beams pass through colimator, water tank and stops in radiochromic film;

• Films were places in the water phantom and positioned with a angle 5 degrees slope to the beam axis in the horizontal plane

Films Scanning

• Reflection Method:

• light from the transmitter bounces off a reflector placed

outside of the housing and travels back to the receiver.

Positive Method:

• a beam of light shines directly from the transmitter to the

receiver.

• An object is detected when it passes between transmitter

and receiver and blocks the beam of light.

Calibration curve

VcbaDose

pixelsV

0,98165c

-34,25479b

-0,84095

a

EBT3 – Positive Method

110 120 130 140 150 160 170 180 190 200 210

0,0

0,5

1,0

1,5

2,0

2,5

3,0

Do

se

(G

y)

Value of pixel

Calibration curve

10 20 30 40 50 60 70 80 90 100 110 120 130 140

0,0

0,5

1,0

1,5

2,0

2,5

3,0

Do

se

(G

y)

Value of Pixel

VcbaDose

EBT3 – Reflective Method

pixels V

0,95327c

-10,01656b

0,12236

a

Comparison between films and planning

system

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Wid

th(m

m)

Depth(mm)

Comparison between EBT2 (black) and Planning System (red) for Positive Method

dL=3mm; dD=3%

G <= 1 (10%): 80.8%

G <= 1 (20%): 72%

G <= 1 (30%): 59%

G <= 1 (40%): 11.5%

G <= 1 (50%): 71%

G <= 1 (60%): 98.6%

G <= 1 (70%): 100%

G <= 1 (80%): 99.4%

G <= 1 (90%): 99.7%

G <= 1 (100%): 100%

G <= 1 (>90%): 99.7%

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idth

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Depth(mm)

Comparison between EBT3 (black) and Planning System (red) for Positive Method

dL=3mm; dD=3%

G <= 1 (10%): 90.4%

G <= 1 (20%): 73.6%

G <= 1 (30%): 58.8%

G <= 1 (40%): 10.6%

G <= 1 (50%): 59.5%

G <= 1 (60%): 91.9%

G <= 1 (70%): 99.6%

G <= 1 (80%): 100%

G <= 1 (90%): 100%

G <= 1 (100%): 100%

G <= 1 (>90%): 100%

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Comparison between EBT2 (black) and Planning System (red) for Reflective Method

dL=3mm; dD=3%

G <= 1 (10%): 59.3%

G <= 1 (20%): 80.3%

G <= 1 (30%): 93.9%

G <= 1 (40%): 58.4%

G <= 1 (50%): 77.4%

G <= 1 (60%): 99.6%

G <= 1 (70%): 97.8%

G <= 1 (80%): 90%

G <= 1 (90%): 80.6%

G <= 1 (100%): 100%

G <= 1 (>90%): 80.7%

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Wid

th(m

m)

Depth(mm)

Comparison between EBT3 (black) and Planning System (red) for Reflective Method

dL=3mm; dD=3%

G <= 1 (10%): 67.5%

G <= 1 (20%): 72.2%

G <= 1 (30%): 87.1%

G <= 1 (40%): 95.8%

G <= 1 (50%): 99.5%

G <= 1 (60%): 93.5%

G <= 1 (70%): 96.1%

G <= 1 (80%): 75.9%

G <= 1 (90%): 71%

G <= 1 (100%): 100%

G <= 1 (>90%): 71.2%

RESULTS

• Positive Method: G – index more 90%

• Reflective Method: G – index less 90%

• Preferable is positive method of scanning

Conclusions

• Radiochromic films are accurate detectors for

proton beam dosimetry

• Measured date are consistent with the date

from PS in the acceptable deviation (3%)

• Results from G – index comply requierement

for the planning of proton therapy

THANK YOU FOR YOUR

ATTENTION !

Special thanks to: My project consultant:

Konstantin Shipulin – Medico-Technical Complex,

Dzhelepov Laboratory of Nuclear Problems,

JINR, Dubna