Distribuzione di radicali liberi in dosimetri EPR ...static.sif.it/SIF/resources/public/files/congr12/Marrale.pdf · Distribuzione di radicali liberi in dosimetri EPR irradiati con

Distribuzione di radicali liberi in dosimetri EPR irradiati con radiazioni di diverso LET

aDipartimento di Fisica, Università di PalermobSezione INFN di Catania Catania

cDipartimento di Scienze Chimiche, Università di Padova e INFN Sezione di PadovadLaboratori Nazionali del Sud-INFN Catania

eMuseo Storico della Fisica e Centro Studi e Ricerche "E. Fermi" RomafAzienda Sanitaria Provinciale N° 2, Pres. Osped. "M. Raimondi" S. Cataldo (CL)

M. Marralea,b, A. Longoa,b, M. Braia,b, A. Barbonc, M. Brustolonc, G.A.P. Cirroned, F. Romanod,e, F. Di Rosaf, G.Cuttoned

E-mail: [email protected]

XCVIII Congresso Nazionale SIF Napoli 17-21 Settembre 2012

M. Marrale et al.– Distribuzione di radicali liberi in dosimetri EPR

Hadrontherapy Hadrontherapy vsvs photon radiotherapy photon radiotherapy









Differences in Relative Biological EffectivenessDifferences in Relative Biological Effectiveness

Hall E. J. (2000). Radiation Biology for the Radiologist. Lippincott Williams & Wilkins: Philadelphia.

The surviving cell fraction decreases with LET

Cell response depends on Linear Energy Transfer (LET)



Differences in Relative Biological EffectivenessDifferences in Relative Biological Effectiveness

Hall E. J. (2000). Radiation Biology for the Radiologist. Lippincott Williams & Wilkins: Philadelphia.

Cucinotta, F. A. & Durante, M. Lancet Oncol. (2006) 7 431-435.

The surviving cell fraction decreases with LET

Cell response depends on Linear Energy Transfer (LET)



Radiation interaction in nanometer dimensions

In order to optimize the therapy it is necessary to grasp the mechanisms on the basis of the biological damages induced by ionizing radiations.



Radiation interaction in nanometer dimensions

In order to optimize the therapy it is necessary to grasp the mechanisms on the basis of the biological damages induced by ionizing radiations.

Analysis of the Analysis of the Track StructureTrack Structure

Figures from Hans Rabus, PTB (Germany)



Target of this workTarget of this work



Target of this workTarget of this work This work is aimed at the analysis of the distribution of free radicals produced by various LET radiations through Electron Spin Resonance (ESR or EPR) technique. This spectroscopic tool allows dose measurements via the detection of the free radicals produced by ionizing radiations.



Target of this workTarget of this work

In this work we analyzed and simulated the experimental results obtained by Pulse ESR techniques with the aim of obtaining information about the microscopic local concentration and the spin-spin distance distribution of free radicals.

This spectroscopic tool allows dose measurements via the detection of the free radicals produced by ionizing radiations.

This work is aimed at the analysis of the distribution of free radicals produced by various LET radiations through Electron Spin Resonance (ESR or EPR) technique.



ORGANIC COMPOUND USED – AMMONIUM TARTRATE (AT)

ESR spectrumSTRUCTURE

.

M. Brustolon, A. L. Maniero, S. Jovine, and U. Segre, Res. Chem. Intermed. 22(4), 359 (1996).

Powder samples



Free radicals distributions for radiations with Free radicals distributions for radiations with various LETvarious LET




Low LET radiations Small local concentrationof free radicals




Low LET radiations

High LET radiations High local concentrationof free radicals

Small local concentrationof free radicals



LET in Ammonium tartrateLET in Ammonium tartrate

— 60Co γ-photons

— 19.3 MeV protons— 0.62 MeV protons (thermal neutrons)

AVERAGE AVERAGE

EFFECTIVE LETEFFECTIVE LET

~ 0.35 keV/~ 0.35 keV/µµmm

~ 4.5 keV/~ 4.5 keV/µµmm

~ 70 keV/~ 70 keV/µµmm

We have used for protons simulations the TRIM software for photon simulations the MCNP software.



Pulsed EPR techniques employed

Two pulses EPR echo decay with varying microwave power intensity in order to obtain information about the microscopic local concentration of free radicals for pellets exposed to various radiation beams.

Double Electron-Electron Resonance (DEER) in order to obtain information about the spin-spin distance distributions for pellets exposed to various radiation beams.



Two pulses EPR echo decay analysisTwo pulses EPR echo decay analysis



AT exposed to 5kGy ofgamma photons.

Tm







Local microscopic concentration of free radicals Local microscopic concentration of free radicals

AVERAGE EFFECTIVE LETAVERAGE EFFECTIVE LET

~ 0.35 keV/~ 0.35 keV/µµmm

~ 4.5 keV/~ 4.5 keV/µµmm

~ 70 keV/~ 70 keV/µµmm

High LET radiations (protons and thermal neutrons) are characterized by larger ratio Cmicroscopic/Cmacroscopic values than low LET radiations.

M. Marrale, M. Brai, A. Barbon, M. Brustolon Radiat. Res. (2009) 171,349–359



Two pulses EPR echo decay analysis Two pulses EPR echo decay analysis ConclusionsConclusions

This technique is able to distinguish low LET This technique is able to distinguish low LET radiations (such as radiations (such as 6060Co Co γγ-photons) from -photons) from high high LET radiations (19.3 MeV protons LET radiations (19.3 MeV protons and thermal and thermal neutrons).neutrons).

The similarity of the microscopic concentrations The similarity of the microscopic concentrations of protons and thermal neutrons could be of protons and thermal neutrons could be ascribed to radicals recombination. ascribed to radicals recombination.



Double Electron-Electron resonance (DEER)Double Electron-Electron resonance (DEER)

Measures dipolar coupling between Measures dipolar coupling between spatially separated unpaired electrons spatially separated unpaired electrons using pulsed EPRusing pulsed EPR

Dipolar coupling is related to radical Dipolar coupling is related to radical separationseparation

Hamiltonian:20

1 2 3 5

. ( . )( . )ˆ 34

1 2 1 2S S S r S rddH g g

r rβµ µπ

= − −



Double electron-electron resonance (DEER)Double electron-electron resonance (DEER)

τ

Δν

Pump

Observe

Δν

Distance / nm2 4 6 8

Time / sμ20

-10 0 10Frequency / MHz

π/2π π

π

Janet BanhamTesting the Limits of the DEER Method for Distance Measurements in Proteins Oxford University




τ

Δν

Pump

Observe

Δν


Time / sμ20


π/2π π

π





τ

Δν

Pump

Observe

Δν


Time / sμ20


π/2π π

π




Double Electron Electron Resonance (DEER)Double Electron Electron Resonance (DEER)

ν pump

ν detection



Distance distributions of free radicalsDistance distributions of free radicals





These curves are affected by two factors:

the lattice structure of the ammonium tartrate microcrystals in powders;

the spatial distribution of free radicals produced by ionizing radiations inside the volume




Free radicals distributions assumed for simulationsFree radicals distributions assumed for simulations




19.3 MeV Protons 19.3 MeV Protons




6060Co Co γγ -photons-photons

19.3 MeV Protons 19.3 MeV Protons




Good agreement Good agreement between experimental between experimental data and simulation data and simulation

results. results.




This pulse EPR technique discriminates samples This pulse EPR technique discriminates samples exposed to exposed to γγ-photons from those exposed to protons.-photons from those exposed to protons.

The radical distributions assumed for protons The radical distributions assumed for protons (cylindrical distribution) and photons (spherical (cylindrical distribution) and photons (spherical distribution) exposure give rise to a good agreement distribution) exposure give rise to a good agreement between experimental data and simulations.between experimental data and simulations.

Double Electron Electron Resonance (DEER)Double Electron Electron Resonance (DEER)ConclusionsConclusions

Analyses on crystal samples exposed to various radiation Analyses on crystal samples exposed to various radiation beams (such as photons, thermal neutrons and ions)beams (such as photons, thermal neutrons and ions)are in progress.are in progress.



AcknowledgementsAcknowledgements

We acknowledge funding from the Project NORMET of theIstituto Nazionale di Fisica Nucleare (INFN) Gruppo V.

National Project Leader: Dr. Maurizio Marrale

The research here described is related to the Project Biologically weighted quantities in radiotherapy (BIOQUART)

EMRP European Metrology Research Programme.Project Leader: Dr. Hans Rabus (PTB, Braunschweig, Germany)



Thank you for your attention!Thank you for your attention!

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