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Dosimetry Studies of Different Radiotherapy Applications using Monte Carlo Radiation Transport Calculations
Uppsala University, Medicinska vetenskapsområdet, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Developing radiation delivery systems for optimisation of absorbed dose to the target without normal tissue toxicity requires advanced calculations for transport of radiation. In this thesis absorbed dose and fluence in different radiotherapy applications were calculated by using Monte Carlo (MC) simulations.

In paper I-III external neutron activation of gadolinium (Gd) for intravascular brachytherapy (GdNCB) and tumour therapy (GdNCT) was investigated. MC codes MCNP and GEANT4 were compared. MCNP was chosen for neutron capture reaction calculations. Gd neutron capture reaction includes both very short range (Auger electrons) and long range (IC electrons and gamma) products. In GdNCB the high-energetic gamma gives an almost flat absorbed dose delivery pattern, up to 4 mm around the stent. Dose distribution at the edges and inside the stent may prevent stent edge and in-stent restenosis. For GdNCT the absorbed dose from prompt gamma will dominate over the dose from IC and Auger electrons in an in vivo situation. The absorbed dose from IC electrons will enhance the total absorbed dose in the tumours and contribute to the cell killing.

In paper IV a model for calculation of inter-cluster cross-fire radiation dose from β-emitting radionuclides in a breast cancer model was developed. GEANT4 was used for obtaining absorbed dose. The dose internally in cells binding the isotope (self-dose) increased with decreasing β-energy except for the radionuclides with substantial amounts of conversion electrons and Auger electrons. An effective therapy approach may be a combination of radionuclides where the high self-dose from nuclides with low β-energy should be combined with the inter-cell cluster cross-fire dose from high energy β-particles.

In paper V MC simulations using correlated sampling together with importance sampling were used to calculate spectra perturbations in detector volumes caused by the detector silicon chip and its encapsulation. Penelope and EGSnrc were used and yielded similar results. The low energy part of the electron spectrum increased but to a less extent if the silicon detector was encapsulated in low z-materials.

Place, publisher, year, edition, pages
Uppsala: Universitetsbiblioteket , 2008. , p. 49
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 375
Keywords [en]
External Beam Radiotherapy, Gadolinium Neutron Capture Therapy, Gadolinium Neutron Capture Brachytherapy, Targeted Radionuclide therapy, Detector Response Modelling, Monte Carlo Simulation.
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
URN: urn:nbn:se:uu:diva-9277ISBN: 978-91-554-7279-5 (print)OAI: oai:DiVA.org:uu-9277DiVA, id: diva2:172515
Public defence
2008-10-11, Fåhreussalen, C5, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 09:15
Opponent
Supervisors
Available from: 2008-09-19 Created: 2008-09-19Bibliographically approved
List of papers
1. Monte Carlo calculations of thermal neutron capture in gadolinium: a comparison of GEANT4 and MCNP with measurements.
Open this publication in new window or tab >>Monte Carlo calculations of thermal neutron capture in gadolinium: a comparison of GEANT4 and MCNP with measurements.
2006 In: Medical Physics, ISSN 0094-2405, Vol. 33, no 2, p. 337-341Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-97526 (URN)
Available from: 2008-09-19 Created: 2008-09-19Bibliographically approved
2. Gadolinium neutron capture brachytherapy (GdNCB), a new treatment method for intravascular brachytherapy.
Open this publication in new window or tab >>Gadolinium neutron capture brachytherapy (GdNCB), a new treatment method for intravascular brachytherapy.
2006 In: Medical Physics, ISSN 0094-2405, Vol. 33, no 1, p. 46-51Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-97527 (URN)
Available from: 2008-09-19 Created: 2008-09-19Bibliographically approved
3. Dosimetry for gadolinium neutron capture therapy (GdNCT)
Open this publication in new window or tab >>Dosimetry for gadolinium neutron capture therapy (GdNCT)
Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-97528 (URN)
Available from: 2008-09-19 Created: 2008-09-19 Last updated: 2010-01-13Bibliographically approved
4. Cross-fire doses from β-emitting radionuclides in targeted radiotherapy: A theoretical study based on experimentally measured tumor characteristics
Open this publication in new window or tab >>Cross-fire doses from β-emitting radionuclides in targeted radiotherapy: A theoretical study based on experimentally measured tumor characteristics
2008 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 53, no 7, p. 1909-1920Article in journal (Refereed) Published
Abstract [en]

A mathematical model based upon histological findings of cell cluster distributions in primary breast cancers and lymph node metastases was developed. The model is unique because it accounts for tumor cell cluster formations within both primary tumors and metastases. The importance of inter-cell cluster cross-fire radiation dose for beta-emitting radionuclides of different energies was studied. The cell clusters were simulated as spheres with 15, 25 and 50 microm radii having a homogeneous radioactivity distribution. The self-dose as well as the dose distribution around the spheres was calculated for seven radionuclides, (90)Y, (188)Re, (32)P, (186)Re, (159)Gd, (131)I and (177)Lu using the GEANT4 Monte Carlo code. Generally, the self-dose was decreasing with increasing energy of the emitted beta particles. An exception was (188)Re which, compared to (32)P, had higher beta energy as well as higher self-dose. This was due to the higher emission of conversion and Auger electrons in the (188)Re-decay. When the cell clusters had a mean distance that was shorter than the maximum range of beta-particles, then the inter-cluster cross-fire radiation contributed significantly to the absorbed dose. Thus, high-energy beta-particles may, in spite of a low self-dose to single clusters, still be favorable to use due to the contribution of inter-cluster cross-fire radiation.

Keywords
Cancer, tumor, radiation, therapy
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-97529 (URN)10.1088/0031-9155/53/7/007 (DOI)000254175900007 ()18364546 (PubMedID)
Available from: 2008-09-19 Created: 2008-09-19 Last updated: 2017-12-14Bibliographically approved
5. Determination of self perturbations of spectra in detectors in photon fields
Open this publication in new window or tab >>Determination of self perturbations of spectra in detectors in photon fields
Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-97530 (URN)
Available from: 2008-09-19 Created: 2008-09-19 Last updated: 2010-01-13Bibliographically approved

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