Dosimetry for synchrotron x-ray microbeam radiation therapy [Elektronische Ressource] / Erik Albert Siegbahn

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• Publié par: technische_universitat_munchen
• Publié le: 01 janvier 2007
• Nombre de lectures: 86
• Langue: English
• Poids de l'ouvrage: 1 Mo

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European Synchrotron Radiation Facility


Dosimetry for synchrotron x-ray
microbeam radiation therapy



Erik Albert Siegbahn




Vollständiger Abdruck der von der Fakultät für Physik der Technischen
Universität München zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften genehmigten Dissertation.


Vorsitzender: Univ.-Prof. Dr. J. L. van Hemmen
Prüfer der Dissertation:

1. Hon.-Prof. Dr. H. G. Paretzke
2. Univ.-Prof. Dr. R. Krücken




Die Dissertation wurde am 13.06.2007 bei der Technischen Universität
München eingereicht und durch die Fakultät für Physik am 05.10.2007
angenommen.
2CONTENTS



1. INTRODUCTION................................................................................................................ 5
1.1 SYNCHROTRON X-RAY MICROBEAM RADIATION THERAPY................................................. 5
1.2 THE ACCURATE DETERMINATION OF ABSORBED DOSES ..................................................... 7
1.2.1 Limits to experimental dosimetry for MRT ............................................................... 8
1.2.1.1 Dose measurements in large homogeneous fields .................................................................... 9
1.2.1.2 Dose measurements in microbeams .................................................................................... 9
1.2.1.3 X-ray spectrum determination........................................................................................... 9
1.2.2 Calculations of the absorbed radiation dose .......................................................... 10
2. INTERACTIONS OF RADIATION WITH MATTER ................................................ 11
2.1 X-RAY INTERACTIONS WITH MATTER RELEVANT FOR MRT............................................. 11
2.1.1 Coherent (Rayleigh) scattering ............................................................................... 13
2.1.2 Incoherent (Compton) ............................................................................ 14
2.1.3 Photoelectric effect.................................................................................................. 14
2.1.4 Atomic relaxation .................................................................................................... 15
2.1.5 Attenuation of x-rays with depth in a medium......................................................... 16
2.2 SECONDARY ELECTRON INTERACTIONS WITH MATTER .................................................... 16
2.2.1 Elastic scattering: 16
2.2.2 Inelastic scattering:................................................................................................. 18
2.3 QUANTITIES USED FOR DESCRIBING THE DEPOSITION OF RADIATION ENERGY.................. 19
2.3.1 Absorbed dose ......................................................................................................... 19
2.3.2 Kerma (Kinetic energy released in matter)............................................................. 20
3. MONTE CARLO SIMULATIONS OF DOSE DEPOSITION ................................... 21
3.1 THE PENELOPE MC CODE ............................................................................................ 21
3.2 SIMULATION GEOMETRY AND DETAILS............................................................................ 22
3.3 DEPTH-DOSE CURVES ...................................................................................................... 22
3.4 TRANSVERSAL DOSE PROFILES ........................................................................................ 24
3.5 SPECTRA AND ANGULAR DISTRIBUTIONS OF SECONDARY PARTICLES .............................. 25
3.6 THE RELATIVE IMPORTANCE OF DIFFERENT INTERACTION PROCESSES............................. 29
3.7 DIFFERENCES IN ABSORBED DOSE FOR DIFFERENT BEAM SIZES........................................ 30
3.8 COMPARISON WITH CALCULATED DOSE PROFILES FROM EARLIER STUDIES...................... 32
3.9 COMPOSITE DOSE DISTRIBUTIONS AND PVDR’S.............................................................. 34
3.10 COMPARISON OF ABSORBED DOSES CALCULATED WITH DIFFERENT MC CODES ............ 40
3.10.1 Dose calculations in water.................................................................................... 40
3.10.2 Dose calculations in PMMA ................................................................................. 42
3.11 MOSFET-DOSIMETER SIMULATIONS............................................................................. 45
3.11.1 Geometry and composition of the MOSFET probe............................................... 46
3.11.2 Simulation model................................................................................................... 47
3.11.3 Simulation results.................................................................................................. 49
3.11.4 Discussion ............................................................................................................. 52
3.12 TREATMENT PLANNING 55
3.12.1 Issues in treatment planning for MRT................................................................... 55
3.12.2 Isodose calculations in homogeneous materials................................................... 55
33.12.3 Simulation of dose deposition in tissue-equivalent phantoms............................... 59
3.12.4 Cross-firing arrays of microbeams ....................................................................... 61
4. EXPERIMENTAL DOSIMETRY .................................................................................. 63
4.1 X-RAY SPECTRUM MEASUREMENTS................................................................................. 63
4. 1. 1 X-ray diffraction.................................................................................................... 63
4. 1. 2 Energy-dispersive x-ray powder diffraction ......................................................... 65
4. 1. 3 Measurement setup................................................................................................ 65
4. 1. 4 Measurement results ............................................................................................. 66
4.2 IONIZATION CHAMBER DOSIMETRY IN LARGE HOMOGENEOUS FIELDS ............................. 69
4.2.1 Theory and method.................................................................................................. 69
4.2.2 Measurement setup 71
4.2.3 Measurement results ............................................................................................... 73
4.2.3.1 Air-kerma measurement by dynamical scanning ................................................................... 73
4.2.3.2 Air-kerma measurement by multiple translations and exposures................................................. 74
4.2.3.3 Half-value layer determination........................................................................................ 76
4.2.4 Discussion ............................................................................................................... 76
4.3 MICROBEAM CHARACTERIZATION................................................................................... 77
4.3.1 Multi-slit collimation of microbeams ...................................................................... 77
4.3.2 Measurements of the microbeam shapes................................................................. 78
4.4 X-RAY MICROBEAM DOSIMETRY...................................................................................... 79
4.4.1 Radiochromic film dosimetry .................................................................................. 80
4.4.1.1 Method.................................................................................................................... 81
4.4.1.2 Results and discussion.................................................................................................. 82
4.4.2 Solid-state detector dosimetry (MOSFET).............................................................. 83
4.4.2.1 Experimental setup...................................................................................................... 84
4.4.2.2 Results 85
4.4.2.2.1 Cross-calibration of the MOSFET.............................................................................. 85
4.4.2.2.2 Transversal dose-profile ......................................................................................... 86
4.4.2.2.3 PVDR’s............................................................................................................. 87
5. SUMMARY ....................................................................................................................... 90
5.1 THEORETICAL DOSIMETRY............................................................................................... 90
5.2 EXPERIMENTAL DOSIMETRY ............................................................................................ 90
REFERENCES....................................................................................................................... 93
APPENDICES. 100
A.1 THE EUROPEAN SYNCHROTRON RADIATION FACILITY (ESRF)......................................... 100
A.2 THE X-RAY SOURCE................................................................................