| 1. |
- Hurkmans, Coen, et al.
(författare)
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Dosimetric verification of open asymmetric photon fields calculated with a treatment planning system based on dose-to-energy-fluence concepts
- 1996
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 41:8, s. 1277-1290
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Tidskriftsartikel (refereegranskat)abstract
- Output normalized dose profiles for asymmetric open photon fields has been calculated using a commercial treatment planning system (TPS) based on a dose-to-energy-fluence concept. The model does not require any additional measurements for off-axis fields. Calculations are compared with measurements for quadratic fields of 5 cm x 5 cm up to 20 cm x 20 cm, with their geometric field centre positioned 10 cm off-axis in the in-plane direction. The measurements include depth doses and profiles in-plane as well as cross-plane for nominal photon energies of 4, 6 and 18 MV x-rays. Both calculated and measured doses are normalized with respect to a 10 cm x 10 cm reference field, therefore making it possible to compare not only the relative distributions but also the absolute dose levels; that is, calculation of monitor units is included. The calculated depth-dose curves are generally in good agreement with measured data with an accuracy at the absolute dose level of 2% at depths beyond the dose maximum. The cross-plane profiles are calculated with an accuracy better than 3% within the field. The 'tilt' towards the collimator central axis of the in-plane profiles is predicted by the model, but is somewhat overestimated at large depths. The system provides the possibility to separate the primary and scattered parts of the dose and the cause of this tilting was studied by comparing calculated phantom-scattering and head-scattering dose profiles for a symmetric 40 cm x 20 cm field to dose profiles for an asymmetric 20 cm x 20 cm field. The tilting is shown to originate from a change both in phantom scattering and in head scattering compared to the case of symmetrical fields. The results indicate that the investigated TPS can calculate dose distributions in open asymmetric fields with a high degree of accuracy, typically better than 2-3%.
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| 2. |
- Hurkmans, Coen, et al.
(författare)
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Limitations of a pencil beam approach to photon dose calculations in the head and neck region
- 1996
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Ingår i: Medical Dosimetry. - : Elsevier BV. - 1873-4022 .- 0958-3947. ; 21:1, s. 38-38
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Tidskriftsartikel (refereegranskat)abstract
- The inherent limitations of a specific pencil beam model have been studied when applied to a cylindrical geometry simulating the neck region. A comparison is made between measured and calculated absorbed dose in a cylindrical phantom. The goal is to quantify the deviations in the absorbed dose level, i.e., the dose per monitor unit, when photons are used for the treatment of head and neck tumours. Square fields ranging from 5 x 5 up to 30 x 30 cm[super:2] are studied for photon beam energies of [super:60]Co, 4, 6 and 18 MV. Ionisation chamber measurements have been performed in the cylinder as well as in two other configurations in order to trace the origin of possible deviations. For 18 MV no significant deviations are found between measurement and calculation in the cylindrical configuration. For the lower energies, an over-estimation of the calculated dose in the cylindrical configuration up to about 6% for a 20 x 20-cm[super:2] [super:60]Co field has been found. These deviations have been traced to the basic approximation for the integration volume for phantom scatter calculations inherent in this pencil beam implementation.
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| 3. |
- Hurkmans, Coen, et al.
(författare)
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Limitations of a pencil beam approach to photon dose calculations in the head and neck region
- 1995
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Ingår i: Radiotherapy and Oncology. - 1879-0887. ; 37:1, s. 74-80
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Tidskriftsartikel (refereegranskat)abstract
- The inherent limitations of a specific pencil beam model have been studied when applied to a cylindrical geometry simulating the neck region. A comparison is made between measured and calculated absorbed dose in a cylindrical phantom. The goal is to quantify the deviations in the absorbed dose level, i.e., the dose per monitor unit, when photons are used for the treatment of head and neck tumours. Square fields ranging from 5 x 5 up to 30 x 30 cm2 are studied for photon beam energies of 60Co, 4, 6 and 18 MV. Ionisation chamber measurements have been performed in the cylinder as well as in two other configurations in order to trace the origin of possible deviations. For 18 MV no significant deviations are found between measurement and calculation in the cylindrical configuration. For the lower energies, an overestimation of the calculated dose in the cylindrical configuration up to about 6% for a 20 x 20-cm2 60Co field has been found. These deviations have been traced to the basic approximation for the integration volume for phantom scatter calculations inherent in this pencil beam implementation.
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| 4. |
- Skripcak, Tomas, et al.
(författare)
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Creating a data exchange strategy for radiotherapy research : Towards federated databases and anonymised public datasets
- 2014
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Ingår i: Radiotherapy and Oncology. - : Elsevier BV. - 0167-8140 .- 1879-0887. ; 113:3, s. 303-309
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Tidskriftsartikel (refereegranskat)abstract
- Disconnected cancer research data management and lack of information exchange about planned and ongoing research are complicating the utilisation of internationally collected medical information for improving cancer patient care. Rapidly collecting/pooling data can accelerate 'translational research in radiation therapy and oncology. The exchange of study data is one of the fundamental principles behind data aggregation and data mining. The possibilities of reproducing the original study results, performing further analyses on existing research data to generate new hypotheses or developing computational models to support medical decisions (e.g. risk/benefit analysis of treatment options) represent just a fraction of the potential benefits of medical data-pooling. Distributed machine learning and knowledge exchange from federated databases can be considered as one beyond other attractive approaches for knowledge generation within "Big Data". Data interoperability between research institutions should be the major concern behind a wider collaboration. Information captured in electronic patient records (EPRs) and study case report forms (eCRFs), linked together with medical imaging and treatment planning data, are deemed to be fundamental elements for large multi-centre studies in the field of radiation therapy and oncology. To fully utilise the captured medical information, the study data have to be more than just an electronic version of a traditional (un-modifiable) paper CRF. Challenges that have to be addressed are data interoperability, utilisation of standards, data quality and privacy concerns, data ownership, rights to publish, data pooling architecture and storage. This paper discusses a framework for conceptual packages of ideas focused on a strategic development for international research data exchange in the field of radiation therapy and oncology.
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