Object: Calibration of Gafchromic EBT3 [1,2 ] Motivation :

Characterization of GafChromic EBT3 films with 60CO and low energy protons for radiobiology dosimetry

F. Ambrosinib, R. Cherubinic, C. De Angelisd, G. Espositod, F. Marracinoa, L. Picardia, M. Pimpinellae, C. Ronsivallea, C. Snelsf, M. A. Tabocchinid, M. Vadruccia

a: ENEA C.R. Frascati, UT. APRAD Radiation Sources Laboratory, Via E. Fermi, 45, 00044, Frascati (RM), Italyb: Sapienza Università di Roma - DIET, via Eudossiana, 18, 00184, Roma, Italyc: INFN-Laboratori Nazionali di Legnaro Viale dell'Università 2, 35020 Legnaro (PD), Italyd: Istituto Superiore di Sanità - Technology and Health Department, Viale Regina Elena 299, 00161 Roma, Italye: ENEA C. R. Casaccia Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti Via Anguillarese, 301 00123 Roma Italyf: ENEA C.R. Casaccia, UT. BIORAD Radiobiology, Via Anguillarese, 301, 00123, Roma, Italy

Biophysics@Rome Conference May 22-23 2014

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Object:Calibration of Gafchromic EBT3 [1,2]

Motivation: Gafchromic EBT3, will be used for radiobiology experiments with V79 cells in the framework of the TOP-IMPLART Project (proton facility under construction at ENEA c.r. Frascati).

Methods:Construction of calibration curves Radiation doses vs optical densities (calculated from measured intensity of film darkening) with two different type of radiation: photon and proton.


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Gafchromic EBT3: self-developing dosimetry film (8”x10”) range of sensitivity 0.01 to > 40 Gy

Configuration Composition

Photons primary standard of adsorbed dose to water for 60Co Rays Italian National Metrology Institute for Ionizing Radiation quantities of ENEA (ENEA-INMRI)

Protons low energy proton beam from INFN-LNL CN 7MV VdG accelerator

Materials:

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Calibration of Gafchromic EBT3 with the primary standard of adsorbed dose to water for 60Co rays Based on a graphite calorimeter measurements [3]. Dose rate was measured with a FARMER NE2571 ionization chamber calibrated in water using graphite calorimeter measurements for dose absolute measurements.

60Co sourceGamma emissions 1,17 and 1,33 MeV

Water phantom with FARMER NE2571 ionization chamber

Housing in PMMA of FARMER NE2571 ionization chamber

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Measurements in a PMMA phantom (25.225.225.2 cm3) equivalent to a water phantom 303030 cm3

EBT3 (3x3 cm2) holder in PMMA

EBT3 holder is positioned 2.66 cm from the surface of the PMMA phantom in front of the source of 60Co , 2.66 cm corresponds to 3.2 cm in water which corresponds the reference calculation of the dose: 99% beam uniformity at 100 cm from the source

Housing of EBT3 holder

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Dose rate calculation is corrected for the decay T1/2=5.27 y and for the end error (ex: delay for door opening Pb lockbox, movement of the source): 4,33 10-3 Gy/s at the time of measurement

EBT3 sample (3x3 cm2) cut out from the same foil. Irradiated at doses: 0.5, 1, 3, 5, 8, 10, 20, 30 Gy

Images of irradiated films: - scanned with Epson Expression 11000XL- analyzed with Picodose software (Red channel because EBT3 are more sensible)- mean value of Intensity and standard deviation are read inside a ROI- Same resaults are obtained with Image J analysis software Epson Expression 11000 XL

Picodose X Pro

0 5000 10000 15000 20000 25000 30000 35000 40000 450000

5

10

15

20

25

30

35

Intensity EBT3 PicodoseIntensity EBT3 Picodose

Intensity red channel

Gy

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Calibration curve from fit of experimental data Dose vs Intensity

D= a × exp(b × Iexp)Iexp= intensity for exposed film

Coefficients (with 95% confidence bounds):a= 6710 (6188, 7232)b= -0.000136 (-0.0001437, -0.0001283)R2= 0.9931error bars= standard deviationDose uncertainty= 1%Intensity uncertainty= standard deviation inside ROI

EBT3 60Co

Characterization of GafChromic EBT3 films with 60CO and low energy dosimetry

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Calibration of Gafchromic EBT3 low energy proton (5 MeV) beam from INFN-LNL CN 7MV VdG accelerator [5]

Schematic view of the proton irradiation facility

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Exit beam line vacuum 10-6 mbar


Circular samples holder

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-Two Au scattering foils of 1 m make the beam homogeneous on a circular surface with a diameter of at least 13 mm in air at 1 cm distance from the window / vacuum.

-EBT3: circular shape with a diameter of 16 mm, inserted, together with a sheet of mylar 50 µm thick, in a cylindrical steel sample holder which exposes an area of 13 mm diameter: It is chosen to use such a configuration sample holder and mylar layer, since the experiments will occur precisely with such a set-up: the V79 cells will have as growth substrate a film of mylar 50 µm.

cylinders steel sample holder

Circular samples holder

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- Center of circular samples holder is fixed on a sledge in axis with the particle beam. By controlling rotation of the holder is possible to irradiate samples in groups of 10 with the same setting of extraction of protons (5 MeV) from the accelerator.

- Proton beam extracted from the accelerator is controlled through a current reading and through a semiconductor detector (silicon manufactured by Ortec 500 m thick)

5 cm

Si detector for fluence F (cm-2) measurements D= 1,6*10-9 LET(keV/µm) F (cm-2)

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- EBT3 sample (Ø 13 mm) cut out from the same foil. Irradiated at doses: 0.5, 1, 3, 3.5, 4.5, 5, 8, 10, 20, 30 Gy. Dose rate 2.1 Gy/min - Same analysis of the films made for the 60Co (see slide 5)

Calibration curve from fit of experimental data Dose vs Intensity

1 1.5 2 2.5 3 3.5x 104

0

500

1000

1500

2000

2500

3000

3500

Intensity (red channel)

Dos

e(cG

y)

EBT3 protons LEGNARO

Measurementsfit

D= a × exp(b × Iexp)Iexp= intensity for exposed film

Coefficients (with 95% confidence bounds):a= 7679 (7131, 8227) b= -0.0001311 (-0.0001377, -0.0001245)R2= 0.9922error bars= standard deviationDose uncertainty= 5%Intensity uncertainty= standard deviation inside ROI

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Calibration of EBT3: comparison 60Co and protons

1 1.5 2 2.5 3 3.5 4x 104

0

500

1000

1500

2000

2500

3000

3500

Intensity (red channel)

Dos

e (c

Gy)

Calibration curves EBT3:Co60-5 MeV protons comparison

Co605 MeV Protons

0 0.2 0.4 0.6 0.8 10

1000

2000

3000

4000

5000

net ODD

ose

(cG

y)

Calibration curves EBT3:Co60-5 MeV protons comparison

Co605 MeV Protons

Clear difference in response of the films EBT3 to the two types of radiation: in particular for the same dose the optical density read following a proton irradiation is lower (viceversa for the intensity of blackening), approximately 14 %, to those relating to radiation with photons.

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TOP-IMPLART: Oncological Therapy with Protons – Intensity Modulated Proton Linear Accelerator for RadioTherapyset up ( ENEA Frascati) and V79 irradiationaccelerator is composed by a sequence of linear sections: -one is a 7 MeV proton linac -other segments will reach 150 MeV. low energy part is used as a facilityfor radiobiology experiments with a vertical and horizontal beam

Sample HolderBending Magnet

Vertical line

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Conclusion

Calibration of EBT3 with 60Co and proton beams of energy 5MeV: were constructed calibration curves vs dose and dose intensity of the red channel vs. netOD, in the dose range from 0.5 Gy to 30 Gy.The comparison of these curves with those built for the calibration of the films with bundles of 60Co showed that for the same dose response of the EBT3 irradiated with protons has an intensity in the red channel that is highest and a lowest blackening, viceversa for the optical density, compared to irradiation with photons.

[1] “GAFCHROMIC EBT3 Scan Handling Guide”, Tecnologie Avanzate

[2] Sorriaux, J. et al. Evaluation of Gafchromic EBT3 films characteristics in therapy photon, electron and proton beams. 2013, Physica Medica 29, 599-606. [3] Guerra AS, Laitano RF, Pimpinella M. Characteristics of the adsorbed dose to water standard at ENEA. Phys. Med. Biol. 41 (1996) 657-674.

[4] Devic S. et al. Dosimetric properties of improved GafChromic films for seven different digitizers . Med Phys 2004;31:2392-401.

[5] Belli M. et al. Proton irradiation facility for radiobiological studies at a 7 MV Van DE Graaff accelerator. Nuclear Instruments and Methods in Physics Research A256 (1987) 576-580

Object: Calibration of Gafchromic EBT3 [1,2 ] Motivation :

Documents

low energy protons

radiobiology experiments

biorad radiobiology

mev water phantom

pmma phantom

dose absolute measurements

roma diet

roma italyf