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Photon pencil kernel parameterisation based on beam quality index
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
2006 (English)In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 78, no 3, 347-351 p.Article in journal (Refereed) Published
Abstract [en]

Background and purpose: New treatment techniques in radiotherapy employ increasing dose calculation complexity in treatment planning. For an adequate check of the results coming from a modern treatment planning system, clinical tools with almost the same degree of generality and accuracy as the planning system itself are needed. To fulfil this need we propose a photon pencil kernel parameterization based on a minimum of input data that can be used for phantom scatter calculations. Through scatter integration the pencil kernel model can calculate common parameters, such as TPR or phantom scatter factors, used in various dosimetric QA (quality assurance) procedures. Material and methods: The proposed model originates from an already published radially parameterized pencil kernel. A depth parameterization of the pencil kernel parameters has been introduced, based on a large database containing commissioned beam data for a commercial treatment planning system. The entire pencil kernel model demands only one photon beam quality index, TPR20,10, as input. Results: By comparing the dose calculation results to the extensive experimental data set in the database, it has been possible to make a thorough analysis of the resulting accuracy. The errors in calculated doses, normalized to the reference geometry, are in most cases smaller than 2%. Conclusions: The investigation shows that a pencil kernel model based only on TPR20,10 can be used for dosimetric verification purposes in megavoltage photon beams at depths below the range of contaminating electrons. (c) 2006 Elsevier Ireland Ltd.

Place, publisher, year, edition, pages
2006. Vol. 78, no 3, 347-351 p.
URN: urn:nbn:se:umu:diva-13486DOI: 10.1016/j.radonc.2006.02.002OAI: diva2:153157
Available from: 2007-02-27 Created: 2007-02-27 Last updated: 2011-03-25Bibliographically approved
In thesis
1. Verification of dose calculations in radiotherapy
Open this publication in new window or tab >>Verification of dose calculations in radiotherapy
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

External radiotherapy is a common treatment technique for cancer. It has been shown that radiation therapy is a both clinically and economically effective treatment for many types of cancer, even though the equipment is expensive. The technology is in constant evolution and more and more sophisticated and complex techniques are introduced. One of the main tasks for physicists at a radiotherapy department is quality control, i.e. making sure that the treatments are delivered in accordance with the dosimetric intentions. Over dosage of radiation can lead to severe side effects, while under dosage reduces the probability for patient cure.

The present thesis is mainly focused on the verification of the calculated dose. Requirements for independent dose calculation software are identified and the procedures using such software are described. In the publications included in the thesis an algorithm specially developed for verification of dose calculations is described and tested. The calculation uncertainties connected with the described algorithm are investigated and modeled. A brief analysis of the quality assurance procedures available and used in external radiotherapy is also included in the thesis.

The main conclusion of the thesis is that independent verification of the dose calculations is feasible in an efficient and cost effective quality control system. The independent calculations do not only serve as a protection against accidents, but can also be the basis for comparisons of the dose calculation performance at different clinics.

Place, publisher, year, edition, pages
Umeå: Strålningsvetenskaper, 2008. 63 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1224
radiotherapy, dose calculation, quality control, pencil kernel
National Category
Radiology, Nuclear Medicine and Medical Imaging
urn:nbn:se:umu:diva-1931 (URN)978‐91‐7264‐679‐7 (ISBN)
Public defence
2008-12-12, 244, By 7, Norrlands universitetssjukhus, Umeå, 09:00 (English)
Available from: 2008-11-24 Created: 2008-11-24 Last updated: 2012-04-02Bibliographically approved

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Nyholm, TufveOlofsson, JörgenAhnesjö, AndersKarlsson, Mikael
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