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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 .

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2 nd annual ardent workshop
2ndAnnual ARDENT Workshop
  • Qualityassessment of hadrontherapy fieldswithTEPCs
  • Paolo Colautti, INFN

2nd Annual ARDENT Workshop, Milano, 14-18 October 2013

slide2

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 1-2 µm sites as the radiation-field microdosimetric quality

The couple of values and is a better quality mark of the radiation field.

Some detectors measure only , which is used as 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 2nd ARDENT workshop. Milano 14-18 October 2013

slide3

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 2nd ARDENT workshop. Milano 14-18 October 2013

slide4

Energy calibration technique in F ~ 1cm cylindrical TEPCs

Tissue-equivalent conductive plastic

Vacuum tide Al cylinder

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide5

Energy calibration technique in F ~ 1mm cylindrical TEPCs

Cathode H.V.

a-source

Gas OUT

a-source

Guard tubes H.V.

Gas IN

Anode pulse

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide6

Measurements at the Nice therapeutic proton beam

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide7

Insulator surfaces damage without electric-field tubes

75 µm

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide8

0.9 mm

0.150 mm

0.9 mm

0.200 mm

Solution: a cavity inside the insulator to switch off the the electronic avalanche

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide9

Mini TEPC of 2.7 mm of external diameter

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide10

Vacuum and gas flow apparatus

Pressure readout

Turbo

pump

Membrane pump

Exhaust

Solenoid valve

MFC

MFC controller

Gas

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide11

Electronic chain

Low LET MCA

Low LET amplifier

Medium LET amplifier

Medium LET MCA

High LET amplifier

High LET

MCA

+18/-6 volt

HVanode

Pulser

HVcathode

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide12

Electronic chain

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide13

Before measuring: linearity checks

Integral linearity

High LET

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide14

Initial data from the 3 MCA

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide15

Volt calibration

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide16

Logaritmic compaction

1st

2nd

Bth

…..

…..

1st

log yi

log yi+1

Equal log intervals

Example: B = 60

First decade y1 = 1.0391, y2 = 1.0798, y3…. Δ1 = 0.04065

Second decade y1 = 10.0391, y2 = 10.0798, y3 …. Δ1 = 0.4065

Countdensity in compactedintervals

Originalcounts

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide17

Sub-spectra junction

Sub-spectra junction is not feasible if they do not superimpose

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide18

The pulse-height frequency distribution

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide19

The pulse-height weighted distribution

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide20

Lineal energy calibration

ICRU 49 data

142 keV/µm

Calibration factor: 142/475 = 0.299

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide21

∆E calculation in CSDA

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide22

Maximum ∆E-lost calculation in CSDA

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide23

Lineal-energy dose distribution

Fractional part of the visual area is the fractional contribution to the the absorbed dose by the corresponding y-events

Blue points are used to linearly extrapolate the frequency y-values down to 0.01 keV/µm

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide24

Weighting the dose distribution with a biological-significant function

Fractional part of the visual area is the fractional contribution to the effective-dose of corresponding y-events

The weight is 1for y-values < 10 keV/µm

The weight is < 1 for y-values ≈> 200 keV/µm

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide25

Splitting the dose spectrum in its neutron and gamma components

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide26

Quality of the conjunctive-melanoma proton-therapeutic beam

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide27

The therapeutic beam quality

Isoeffective-dose map

Iso dose map

Iso RBEµ map

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide28

Two mini TEPCs for quality measurements of BNCT radiation fields

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide29

The twin TEPC for BNCT

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013

slide31

Suggested lectures

  • Glenn F.Knoll. Radiation Detection and Measurements. John Wiley & Sons, NY, 1979
  • ICRU Report 36. Microdosimetry. 1983

P.Colautti 2nd ARDENT workshop. Milano 14-18 October 2013