presentation røros

8/3/2019 Presentation Rros

1/31

Neutron Dosimetry in

Radiotherapy

Kristian Ytre-Hauge

Department of Physics

and Technology

University of Bergen

Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization

Neutron Spectra in the

Medical Linac Room

Carbon Beam

Measurements

Conclusion

Neutron Dosimetry in Radiotherapy

Kristian Ytre-Hauge

Department of Physics and TechnologyUniversity of Bergen

August 2009
http://-/?-http://-/?-http://find/http://goback/http://-/?-http://-/?-


2/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Introduction

About 50% of all cancer patients receive radiotherapy
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3/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Introduction


The aim of radiotherapy is to damage cancer cells whilesparing healthy tissue
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4/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Introduction



Most common is the use of an external photon beam


5/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Introduction



Most common is the use of an external photon beam Hadron therapy is an alternative which has received increasing

interest over the last decades


6/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Introduction



Most common is the use of an external photon beam Hadron therapy is an alternative which has received increasing

interest over the last decades

Neutrons are produced during the treatment and contributeto a higher dose in healthy tissue


7/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Linear accelerator for radiotherapy with photons

Photon energies between 6 and 18 MeV are the mostcommon to use


8/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Neutron contamination of the photon beam

Neutrons are mainly produced through (,n) reactions in the

high-Z material used for shielding and shaping the photonbeam


9/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Neutron contamination of the photon beam

Neutrons are mainly produced through (,n) reactions in the

high-Z material used for shielding and shaping the photonbeam


10/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Principles of hadron therapy

Protons, 12C-ions or other ions are accelerated to energies upto about 400 MeV/u


11/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Secondary particles from hadron therapy

Neutrons, protons and fragments lighter than the primaryparticles are produced through nuclear reactions and maycontribute to dose outside the target volume


12/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Dosimetry

Absorbed dose (D)Defined as the energy deposited per unit mass, D = E

m

The unit for absorbed dose is the Gray [Gy]


13/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Dosimetry

Absorbed dose (D)Defined as the energy deposited per unit mass, D = E

m

The unit for absorbed dose is the Gray [Gy]

Equivalent dose (HT)The absorbed dose is weighted by a quality factor dependingon the type of radiationHT = wRDR

The unit for equivalent dose is the Sievert [Sv]

N D i i


14/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Neutron detectors

BF3 proportional counter

3He proportional counter

6

Li-based scintillators Thin film breakdown counter - Fission counter

Thermoluminescence detectors

Bubble detectors

N t D i t i


15/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Physical principles of bubble detectors

Superheated droplets dispersed throughout a clear plasticpolymer



16/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion



A liquid is said to be superheated if it continues to exist inthe liquid state above its normal boiling point



17/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion




The droplets are vaporized into bubbles if sufficient energy isdeposited in the droplet


f


18/31


Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion




The droplets are vaporized into bubbles if sufficient energy isdeposited in the droplet

The number of bubbles is proportional to the equivalent dose


B bbl D S (BDS)


19/31

y

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Bubble Detector Spectrometer (BDS)

6 different energy thresholds


B bbl D S (BDS)


20/31

y

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Bubble Detector Spectrometer (BDS)

6 different energy thresholds

Unfolding of the response from all the subgroups gives aneutron energy spectrum represented by a 6-region histogram


Ph t b t


21/31

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Photon beam setup

The bubble detectors were placed inside the phantom and a15 MeV photon beam applied


T t d d f th BDS d t t


22/31

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Temperature dependence of the BDS detectors

The response from the BDS detectors was measured at 15

,20

and 25


R di hTe e at e de e de ce of the BDS detecto s


23/31

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble Detector

Characterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Temperature dependence of the BDS detectors

The response from the BDS detectors was measured at 15

,20

and 25

An increase in the temperature of 5

can lead to an increasein the response of more than 100%


RadiotherapMeasurement setup in the isocenter plane


24/31

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors

Bubble DetectorCharacterization


Medical Linac Room

Carbon Beam

Measurements

Conclusion

Measurement setup in the isocenter plane

without the phantom


RadiotherapyComparison of the obtained neutron spectrum


25/31

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors



Medical Linac Room

Carbon Beam

Measurements

Conclusion

Comparison of the obtained neutron spectrum

with Monte Carlo simulations

Energy [MeV]-210 -110 1 10

Fluence[n/(cm2

Gy)]

610

710

810

Neutron spectrum measured with the BDS in the isocenter plane without the phantom


RadiotherapyResults from the photon beam measurements


26/31

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors



Medical Linac Room

Carbon Beam

Measurements

Conclusion

Results from the photon beam measurements -

Dose

Placement of detectors1 2 3 4 5 6 7 8

Neutrondose[mSv/Gy]

0

2

4

6

8

10

12

141 - Isocenter plane

2 - MC simulations isocenter plane

3 - Position 8

4 - Position 8 Closed MLCs

5 - Position 9

6 - Position 9 closed MLCs

7 - Position 14

8 - Position 15

Neutron dose for various positions


RadiotherapyCarbon Beam Measurements Setup


27/31

Radiotherapy

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors



Medical Linac Room

Carbon Beam

Measurements

Conclusion

Carbon Beam Measurements - Setup


RadiotherapyConclusion


28/31

py

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors



Medical Linac Room

Carbon Beam

Measurements

Conclusion

Conclusion

Bubble detectors are a good alternative to measure neutrondoses in radiotherapy


http://goforward/http://find/http://goback/http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


29/31

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors



Medical Linac Room

Carbon Beam

Measurements

Conclusion

Conclusion


The bubble detectors sensitivity varies strongly withtemperature




30/31

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors



Medical Linac Room

Carbon Beam

Measurements

Conclusion

Conclusion


The bubble detectors sensitivity varies strongly withtemperature

Neutron doses from photons were found to be in the order ofmSv per Gray


Radiotherapy


31/31

Kristian Ytre-Hauge


and Technology


Introduction

Radiotherapy with

Photons

Radiotherapy with

Hadrons

Dosimetry

Neutron Detectors



Medical Linac Room

Carbon Beam

Measurements

Conclusion

Thank you!
http://goforward/http://find/http://goback/http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-

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