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Evaluation of a metal artifact reduction algorithm in CT studies used for proton radiotherapy treatment planning
Department of Medical Physics, Örebro University Hospital, Örebro, Sweden.
Uppsala University, Uppsala, Sweden.
Skandionkliniken, Uppsala, Sweden..
2014 (English)In: Journal of Applied Clinical Medical Physics, ISSN 1526-9914, E-ISSN 1526-9914, Vol. 15, no 5, p. 112-119Article in journal (Refereed) Published
Abstract [en]

Metal objects in the body such as hip prostheses cause artifacts in CT images. When CT images degraded by artifacts are used for treatment planning of radiotherapy, the artifacts can yield inaccurate dose calculations and, for particle beams, erroneous penetration depths. A metal artifact reduction software (O-MAR) installed on a Philips Brilliance Big Bore CT has been tested for applications in treatment planning of proton radiotherapy. Hip prostheses mounted in a water phantom were used as test objects. Images without metal objects were acquired and used as reference data for the analysis of artifact-affected regions outside of the metal objects in both the O-MAR corrected and the uncorrected images. Water equivalent thicknesses (WET) based on proton stopping power data were calculated to quantify differences in the calculated proton beam penetration for the different image sets. The WET to a selected point of interest between the hip prostheses was calculated for several beam directions of clinical relevance. The results show that the calculated differences in WET relative to the reference case were decreased when the O-MAR algorithm was applied. WET differences up to 2.0 cm were seen in the uncorrected case while, for the O-MAR corrected case, the maximum difference was decreased to 0.4 cm. The O-MAR algorithm can significantly improve the accuracy in proton range calculations. However, there are some residual effects, and the use of proton beam directions along artifact streaks should only be used with caution and appropriate margins.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014. Vol. 15, no 5, p. 112-119
Keywords [en]
metal artifact reduction, radiation therapy, water equivalent thickness, proton range
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
URN: urn:nbn:se:oru:diva-65011DOI: 10.1120/jacmp.v15i5.4857ISI: 000345121900010PubMedID: 28297224Scopus ID: 2-s2.0-84929502869OAI: oai:DiVA.org:oru-65011DiVA, id: diva2:1182892
Available from: 2018-02-15 Created: 2018-02-15 Last updated: 2018-02-15Bibliographically approved
In thesis
1. Metal artifacts in computed tomography: impact of reduction methods on image quality and radiotherapy treatment planning
Open this publication in new window or tab >>Metal artifacts in computed tomography: impact of reduction methods on image quality and radiotherapy treatment planning
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Degradation of image quality by metal artifacts is a common problem in computed tomography (CT) imaging, which can limit the diagnostic value of a CT examination and also introduce inaccuracies in radiotherapy (RT) treatment planning. In recent years, commercial metal artifact reduction (MAR) methods have been launched by several CT vendors. The overall aim of this thesis was to evaluate MAR methods in diagnostic imaging and RT treatment planning.

Evaluations of hip prosthesis phantom CT images showed that MAR algorithms in general improved image quality, based on both visual grading analysis and quantitative measures, while the application of virtual monoenergetic reconstructions insufficiently reduced metal artifacts. In some cases additional artifacts were introduced by the MAR algorithms. MAR algorithms were also evaluated in hip prosthesis phantom CT imaging used for proton therapy treatment planning, where improvements in dose calculation accuracy were observed.

Studies of Head & Neck (H&N) implant CT images in RT treatment planning were also performed. By visual grading of anatomy visualization with respect to target delineation in dental implant patient images, MAR algorithms were shown to significantly improve image quality. However, only minor effects of H&N implant artifacts on proton dose distributions were seen. The impact might be greater for more severe artifacts than those studied here, and thus further investigations of such cases are needed.

In conclusion, MAR algorithms have been shown to enhance image quality for diagnostic applications and to improve anatomy visualization in RT treatment planning. The MAR algorithms led to increased proton dose calculation accuracy in some cases, while in other situations only minor changes were seen.

Place, publisher, year, edition, pages
Örebro: Örebro University, 2018. p. 81
Series
Örebro Studies in Medicine, ISSN 1652-4063 ; 172
Keywords
computed tomography, metal artifacts, image quality, visual grading analysis, radiotherapy, proton therapy, hip prosthesis, dental implants
National Category
Surgery
Identifiers
urn:nbn:se:oru:diva-63420 (URN)978-91-7529-228-1 (ISBN)
Public defence
2018-03-09, Örebro universitet, Campus USÖ, hörsal C3, Södra Grev Rosengatan 32, Örebro, 09:30 (Swedish)
Opponent
Supervisors
Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2018-02-15Bibliographically approved

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Andersson, Karin M.

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