p. scampoli - 24th icnts bologna, september 4, 2008 1

P. Scampoli - 24th ICNTS Bologna, September 4, 2008P. Scampoli - 24th ICNTS Bologna, September 4, 2008 11


What is common in RT and Space explorationWhat is common in RT and Space exploration

Mixed fields of charged particles are present in Mixed fields of charged particles are present in astronauts environment and patients treated with astronauts environment and patients treated with carbon ionscarbon ions

Dose calculation and radiological risk Dose calculation and radiological risk assessment assessment

Nuclear measurements are needed Nuclear measurements are needed Radiobiological measurements are neededRadiobiological measurements are needed


Heavy ion fragmentationHeavy ion fragmentation

The HZE particles of CGR The HZE particles of CGR produce secondary particles produce secondary particles both in human body, and in both in human body, and in needed shielding materials needed shielding materials

Change in the beam qualityCarbon ions in radiation Carbon ions in radiation therapy undergo therapy undergo fragmentations inside the fragmentations inside the patient bodypatient body


Radiation field in SpaceRadiation field in Space Trapped radiationTrapped radiation: Van Allen belts (electrons, protons up to : Van Allen belts (electrons, protons up to

600 MeV)600 MeV)

Solar radiationSolar radiation: about 90% protons, E<1 GeV, seldom but : about 90% protons, E<1 GeV, seldom but potentially dangerous (high dose) eventspotentially dangerous (high dose) events

Galactic Cosmic Radiation (GCR)Galactic Cosmic Radiation (GCR):: 2% electrons and positrons 2% electrons and positrons 98% particles : 98% particles :

87% protons 87% protons 12% 12% particles particles 1% heavier ions (1% heavier ions (HZE particlesHZE particles))


GCR charge contributionGCR charge contribution

Dose eq. on EarthEarth: 10 Sv/d

Dose eq. on MarsMars: 100-200 mSv/d

Dose eq. on MoonMoon: 300-400 mSv/d

Dose eq. from GCRGCR: 1 mSv/d


DNA dsb visualized by immuno-fluorescence of -H2AX histone in human skin fibroblasts exposed to 2 Gy of ionizing radiation

-rays

silicon

ironCucinotta and Durante, Lancet Oncol. 2006


Risk associated to a manned Space Risk associated to a manned Space explorationexploration

CarcinogenesisCarcinogenesis

Acute Radiation SicknessAcute Radiation Sickness

Degenerative Tissue Damage (heart, lens, Degenerative Tissue Damage (heart, lens,

digestive, …)digestive, …)

Central Nervous System damageCentral Nervous System damage


Uncertainties for risk estimationUncertainties for risk estimation

)()( LLQLdLFHT

T

TT HsexageRdosesexageRisk ),(),,( ,0

Overall uncertainty:

400-1500%


Carbon-ion therapyCarbon-ion therapy

An extensive database on nuclear fragmentation cross sections and fluences are needed at therapeutic energy region

Carbon ions fragmentation:

Fall of dose in the tumour target region

Unwanted dose in normal tissue behind the target volume


Radiation-biophysics needsRadiation-biophysics needs

Biology

Assessment of the biological effects of HZE particles

Physics

•Assessment of the radiation environment

•Shielding optimization


Biological effects in mixed radiation fieldBiological effects in mixed radiation field

Biophysical model of radiation actionBiophysical model of radiation action

Model for determining the ion track Model for determining the ion track structure and energy deposition at local structure and energy deposition at local levellevel

Experimental measurements are essential for benchmarking physics models and transport code to give fluence, energy, and dose distribution with the required accuracy


Ground-based experimentsGround-based experiments


Experimental configuration for mixed radiation Experimental configuration for mixed radiation field studies and shielding optimizationfield studies and shielding optimization

Physics Beam

detector detector

Target

Radiobiology

Target IC


Thick and thin targets Thick and thin targets

Physics

Beam

detector detector

Target

i

iiLD 6.1

iii

i LLQdLLDLQD

DQDH 1

Thick target=

fluence measurements

Thin target=

cross section measurements


CR39 SSNTD in ground-based experiments CR39 SSNTD in ground-based experiments

p2

2

LET

LET

Z

Z

p

2Z

LET

pp LET

LETZZ

LET spectrum measurement through appropriate calibration

Geometrical track parameters measurement

Fe 114 MeV/nLET 414 keV/m

D = 62 m

Fe 1000 MeV/n LET 147 keV/m

Si 600 MeV/n LET 50 keVm

D = 46 mD = 35 m

Etching condition:6 N NaOH water solutiont=24hT=70°C


CR39 SSNTD in ground-based experimentsCR39 SSNTD in ground-based experiments

Very good charge Very good charge resolution resolution

Easy to useEasy to use

LET threshold LET threshold ((~keV/~keV/m)m)

Low fluence irradiation Low fluence irradiation (10(1033 p/cm p/cm22))

Track analysis cannot Track analysis cannot be done manuallybe done manually

ADVANTAGES LIMITATIONS


Automatic track analysis systems Automatic track analysis systems

Microscope development for image digitization

Yasuda et al., Radiat. Meas., 2005

Tawara et al., NIM A., 2008


Cross section measurements (“thin” target)Cross section measurements (“thin” target)

Fe, 1 GeV/n Fe, 1 GeV/n+1 cm PMMA

Cecchini S. et al., Nucl. Phys., 2008

INTERCAST CR39Etching condition:6 N NaOH water solutiont=30 hT=70°C

targ

et


5 10 15 20 25 30 35 40

500

1000

1500

2000

2500

3000

Zeitling et al. Scampoli et al.

Cross section measurementsCross section measurements

Cecchini S. et al., Nucl. Phys., 2008

Database:Database:

Ion Energy range Target

4He; 6C; 14N, 16C; 20Ne; 28Si; 40Ar; 48Ti 0.2 – 10 A GeV CH2; PMMA; C; Al; Cu; Pb


Measurements with “thick” targetMeasurements with “thick” target

Same condition as biological experimentsSame condition as biological experiments

Fe, E=1 A GeV

Measurements of primary beam contribution to the total dose after different shielding materials


Shielding properties of different materialsShielding properties of different materials

Scampoli P. et al., Radiat. Res., 2005

Surviving fraction of incoming particles after different shielding materials is measured with CR39 Intercast detectors

1 A GeV 5 A GeV


Biological effectiveness of shieldingBiological effectiveness of shielding

20

25

30

35

40

45

0 2 4 6 8 10 12

PMMAAlPb

Thickness (g/cm2)

Ab

err

atio

ns

pe

r p

art

icle

(µ

m2)

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0 5 10 15 20 25 30

PMMAAlPbLDPEC

Do

se p

er

pa

rtic

le (

µG

y x

cm2)

Thickness (g/cm2)

500 MeV/n

1 GeV/n

5

10

15

20

25

30

35

0 5 10 15 20 25 30

PMMAAlPbLDPEC

Abe

rrat

ions

per

par

ticle

(µ

m2)

Thickness (g/cm2)

Durante et al., Radiat. Res, 2005

500 A MeV 1 A GeV

Fe beam


Measurements with carbon ions for RTMeasurements with carbon ions for RT

Energies up to 500 A MeV

Track etched detector are used with suitable etching condition

Emulsion detector

Low fluence

Z ≤ 6e

Target: tissue equivalent material

Analysis


Emulsion Cloud ChamberEmulsion Cloud Chamber

Toshito. et al., Phys. Rev. C., 2008

High spatial resolution (~m)

Multiparticle separation

Density grain is proportional to energy loss

Refreshing method for extending the dynamic range of response

High angular resolution (~mrad)


Cross section measurementsCross section measurements

Toshito. et al., Phys. Rev. C., 2008

Shall et al., Nim B, 1996Golovchenko et al., Nim B, 1996 and Phys. Rev. C 2002

Golovchenko et al., Nim B, 1996 and Phys. Rev. C 2002

Golovchenko et al., Nim B, 1996 and Phys. Rev. C 2002

Good agreement with previous experimental data

Discrepancy of about 10% and 20% with model


ConclusionsConclusions

Ground based experiments are still necessary for code bench marking, both in Space radiation-protection and radio-therapy with carbon ions

Shielding properties of new material (e.g. Kevlar and Nextel) have to be investigated

Development of technology make more suitable track-etch detectors for these purposes

p. scampoli - 24th icnts bologna, september 4, 2008 1

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