energy transfer mechanisms and applications in biology and ... · energy transfer mechanisms and...
TRANSCRIPT
0 1 2 3 4 5 6 7 8
0.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
1 10 100
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.1
4.2
6.2
6.6
6.8
6.9
7.0
dose (
Gy)
depth (cm)
97.4 MeV protons
measurement points
yd(y
)
y (keV/mm)
depth in water:
2.1
4.2
6.2
6.6
6.8
6.9
7.0
Energy transfer mechanisms and applications in biology and physics: MICRODOSIMETRY
Introduction
Methodology
Expected outcome
Comparison of microscopic local dosedistributions of C ions and photons for thesame dose of 2 Gy.M. Scholz et al., Rad. Env. Biophys. (1997).
Macroscopic approach:
energy deposition in large volume concept such as absorbed dose is based on sufficiently large volumes and time spans to treat energy deposition as a
continuous process along the particle track, regardless its stochastic nature
Microscopic approach:
energy deposition in cell-size volume study of the whole energy deposition process results are expressed as energy deposition events probabilities energy deposition by densely ionizing radiation is much more heterogeneous
Nuclei of human fibroblasts exposed to γ-rays, Siand Fe ions. Green spot corresponds to a DNAdouble-strand break.F.A. Cucinotta, M. Durante, Lancet Oncol. (2006).
Radiation effects in matter are closely related to spatial distribution of energy deposition.
Microdosimetry concept (Rossi, 1959)
study of the whole energy deposition process methodology involves measurement of stochastic energy deposition distributions main quantities: specific energy (z) and lineal energy (y) links physical features of track structure with biological and clinical outcomes
Tissue-Equivalent Proportional Counter (TEPC):
gaseous proportional counters, scaled by gas density to cellular volumes of μm walls (A150) and fill gas (propane) mimic elemental composition of biological tissue results are expressed as energy deposition events probabilities for z or y pulse height analysis of the output generates energy spectrum
Diamond detector:
collaboration of University of Rome Tor Vergataand MedAustron
novel microdosimeter based on artificial singlecrystal diamond
thermally conductive tissue-equivalent very small sizes
Establishment of procedures for microdosimetric characterisation of clinical proton and carbon beams.
Development of a multi-parameter microdosimetric model for proton and carbon beams.
Correlation of microdosimetric spectra of the energy imparted at cellular level with the biological effect of the ion beams.
Validation of the established microdosimetric procedures with Monte Carlo methods.
Standard microdosimeter, TEPC.H. H. Rossi, Radiat. Res. 10, 522 (1959).
Microdosimetric spectra for 194 MeV/ucarbon, measured around Bragg peak.R. Gerlach et al., RPD, (2002).
Microdosimetric spectra for 97.4 MeVprotons, measured at indicated points.Measured at MedAustron, unpublished
Schematic representation of a diamondbased microdosimeterC. Verona et al., Radiat. Meas. (2018).
TU Wien: Monika Puchalska, Cynthia Meouchi MedAustron: Giulio Magrin, Hugo Palmans
When energy deposition is considered at a scale of cellular and subcellular structures,its stochastic nature is evident and the biological effects (e.g. cell killing) depend onthe density of the ionization.