2 nd ANNUAL ARDENT WORKSHOP Quality assessment of
- Slides: 31
2 nd ANNUAL ARDENT WORKSHOP Quality assessment of hadrontherapy fields with TEPCs Paolo Colautti, INFN 2 nd Annual ARDENT Workshop, Milano, 14 -18 October 2013
The radiation quality concept The radiation field quality is meant as a physical measurable quantity, which is significant for primary effects on a biological system We define the measured y-spectrum in 12 µm sites as the radiation-field microdosimetric quality Some detectors measure only , which is used as quality mark of the radiation field. The couple of values and is a better quality mark of the radiation field. RBEµ, the microdosimetric assessment of RBE, can be an accurate quality mark for a given biological end-point. P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Therapeutic beam constrains Fluence rates Proton continuos beam BNCT facility CNAO protons per spill CNAO carbon ions per spill 1 cm TEPC ought to measure at counting rates bigger than 106 s-1 1 mm TEPC will measure at counting rates bigger than 104 s-1 P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Energy calibration technique in F ~ 1 cm cylindrical TEPCs Tissue-equivalent conductive plastic Vacuum tide Al cylinder P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Energy calibration technique in F ~ 1 mm cylindrical TEPCs Cathode H. V. a-source Gas OUT a-source Guard tubes H. V. Gas IN Anode pulse P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Measurements at the Nice therapeutic proton beam P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Insulator surfaces damage without electric-field tubes 75 µm P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Solution: a cavity inside the insulator to switch off the electronic avalanche 0. 9 mm 0. 150 mm 0. 200 mm P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Mini TEPC of 2. 7 mm of external diameter P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Vacuum and gas flow apparatus Pressure readout Exhaust Membrane pump Turbo pump Solenoid valve MFC controller MFC Gas P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Electronic chain Low LET MCA Low LET amplifier Medium LET MCA Medium LET amplifier High LET MCA High LET amplifier +18/-6 volt Pulser HVanode HVcathode P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Electronic chain P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Before measuring: linearity checks Integral linearity High LET P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Initial data from the 3 MCA P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Volt calibration P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Logaritmic compaction Equal log intervals 1 st 2 nd 1 st log yi …. . Bth log yi+1 Example: B = 60 First decade y 1 = 1. 0391, y 2 = 1. 0798, y 3 …. Δ 1 = 0. 04065 Second decade y 1 = 10. 0391, y 2 = 10. 0798, y 3 …. Δ 1 = 0. 4065 Original counts Count density in compacted intervals P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Sub-spectra junction is not feasible if they do not superimpose P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
The pulse-height frequency distribution P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
The pulse-height weighted distribution P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Lineal energy calibration ICRU 49 data 142 ke. V/µm Calibration factor: 142/475 = 0. 299 P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
∆E calculation in CSDA P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Maximum ∆E-lost calculation in CSDA P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Lineal-energy dose distribution Blue points are used to linearly extrapolate the frequency yvalues down to 0. 01 ke. V/µm Fractional part of the visual area is the fractional contribution to the absorbed dose by the corresponding y -events P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Weighting the dose distribution with a biological-significant function The weight is 1 for y-values < 10 ke. V/µm The weight is < 1 for y-values ≈> 200 ke. V/µm Fractional part of the visual area is the fractional contribution to the effective-dose of corresponding yevents P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Splitting the dose spectrum in its neutron and gamma components P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Quality of the conjunctive-melanoma proton-therapeutic beam P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
The therapeutic beam quality Iso effective-dose map Iso RBEµ map P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
Two mini TEPCs for quality measurements of BNCT radiation fields P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
The twin TEPC for BNCT P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
BNCT dose components twin TEPC measurements 30
Suggested lectures • Glenn F. Knoll. Radiation Detection and Measurements. John Wiley & Sons, NY, 1979 • ICRU Report 36. Microdosimetry. 1983 P. Colautti 2 nd ARDENT workshop. Milano 14 -18 October 2013
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