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

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slide1

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 RadiationSourcesLaboratory, Via E. Fermi, 45, 00044, Frascati (RM), Italy

b: Sapienza Università di Roma - DIET, via Eudossiana, 18, 00184, Roma, Italy

c: INFN-Laboratori Nazionali di Legnaro Viale dell'Università 2, 35020 Legnaro (PD), Italy

d: Istituto Superiore di Sanità - Technology and HealthDepartment, Viale Regina Elena 299, 00161 Roma, Italy

e: ENEA C. R. Casaccia Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti Via Anguillarese, 301 00123 Roma Italy

f: ENEA C.R. Casaccia, UT. BIORAD Radiobiology, Via Anguillarese, 301, 00123, Roma, Italy

Biophysics@Rome Conference May22-23 2014

slide2

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

Object:

Calibration of Gafchromic EBT3 [1,2]

Motivation:

Gafchromic EBT3, willbe usedfor radiobiologyexperiments with V79 cells in the framework of the TOP-IMPLART Project (protonfacilityunder constructionat ENEA c.r. Frascati).

Methods:

Construction of calibration curves

Radiation doses vs optical densities (calculated from measured intensity of film darkening) with twodifferenttype of radiation: photon and proton.

slide3

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

Materials:

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

ConfigurationComposition

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

Protonslowenergyprotonbeam from INFN-LNL CN 7MV VdGaccelerator

slide4

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

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  source

Gamma emissions

1,17 and 1,33 MeV

Water phantom with FARMER NE2571 ionization chamber

Housing in PMMA of FARMER NE2571 ionization chamber

slide5

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

Measurements in a PMMA phantom (25.225.225.2 cm3)equivalent to a water phantom

303030 cm3

Housing of EBT3 holder

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 whichcorresponds the reference calculation of the dose: 99% beam uniformity at 100 cm from the source

slide6

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

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, movementof the source): 4,33 10-3Gy/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 irradiatedfilms:

- scanned with Epson Expression 11000XL

- analyzed with Picodose software (Redchannelbecause EBT3 are more

sensible)

- meanvalue of Intensity and standard deviation are read inside a ROI

- Sameresaults are obtained with Image J analysissoftware

Epson Expression 11000 XL

Picodose X Pro

slide7

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

Calibration curve from fit of experimental dataDose vs Intensity

EBT3 60Co

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= 0.9931

errorbars= standard deviation

Dose uncertainty= 1%

Intensityuncertainty= standard deviationinside ROI

slide9

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

Calibration of Gafchromic EBT3 lowenergyproton (5 MeV) beam from INFN-LNL CN 7MV VdGaccelerator[5]

Schematic view of the proton irradiation facility

slide10

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

Calibration of Gafchromic EBT3 lowenergyproton (5 MeV) beam from INFN-LNL CN 7MV VdGaccelerator[5]

Schematic view of the proton irradiation facility

slide11

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

Calibration of Gafchromic EBT3 lowenergyproton (5 MeV) beam from INFN-LNL CN 7MV VdGaccelerator[5]

Schematic view of the proton irradiation facility

Circularsamplesholder

Exit beam line vacuum 10-6mbar

slide12

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

-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.

Circularsamplesholder

cylinders steel sample holder

slide13

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

-Center of circularsamplesholderisfixed 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)

Si detector for fluence F (cm-2) measurements

D= 1,6*10-9  LET(keV/µm)  F (cm-2)

5 cm

slide14

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

- 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 dataDose vs Intensity

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=0.9922

errorbars= standard deviation

Dose uncertainty= 5%

Intensityuncertainty= standard deviationinside ROI

slide16

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

Calibration of EBT3: comparison 60Co and 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 (viceversafor the intensity of blackening), approximately 14 %, to those relating to radiation with photons.

slide17

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

TOP-IMPLART: Oncological Therapy with Protons – Intensity Modulated Proton Linear Accelerator for RadioTherapyset up ( ENEA Frascati) and V79 irradiation

accelerator 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 facility

for radiobiology experiments with a vertical

and horizontal beam

Sample Holder

Bending Magnet

Vertical line

slide18

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

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, viceversafor the optical density, compared to irradiation with photons.

[1] “GAFCHROMIC EBT3 Scan Handling Guide”, TecnologieAvanzate

[2] Sorriaux, J. et al. Evaluation of Gafchromic EBT3 films characteristics in therapy photon, electron and proton beams. 2013, PhysicaMedica 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. Dosimetricproperties 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