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Multi-institutional study of the variability in target delineation for six targets commonly treated with radiosurgery
Stockholm University, Faculty of Science, Department of Physics. Karolinska Institutet, Sweden.
Stockholm University, Faculty of Science, Department of Physics. Karolinska Institutet, Sweden.ORCID iD: 0000-0002-7101-240X
2018 (English)In: Acta Oncologica, ISSN 0284-186X, E-ISSN 1651-226X, Vol. 57, no 11, p. 1515-1520Article in journal (Refereed) Published
Abstract [en]

Background: Although accurate delineation of the target is a key factor of success in radiosurgery there are no consensus guidelines for target contouring.

Aim: The aim of the present study was therefore to quantify the variability in target delineation and discuss the potential clinical implications, for six targets regarded as common in stereotactic radiosurgery.

Material and methods: Twelve Gamma Knife centers participated in the study by contouring the targets and organs at risks and performing the treatment plans. Analysis of target delineation variability was based on metrics defined based on agreement volumes derived from overlapping structures following a previously developed method. The 50% agreement volume (AV50), the common and the encompassing volumes as well as the Agreement Volume Index (AVI) were determined.

Results: Results showed that the lowest AVI (0.16) was found for one of the analyzed metastases (range of delineated volumes 1.27–3.33 cm3). AVI for the other two metastases was 0.62 and 0.37, respectively. Corresponding AVIs for the cavernous sinus meningioma, pituitary adenoma and vestibular schwannoma were 0.22, 0.37 and 0.50.

Conclusions: This study showed that the variability in the contouring was much higher than expected and therefore further work in standardizing the contouring practice in radiosurgery is warranted.

Place, publisher, year, edition, pages
2018. Vol. 57, no 11, p. 1515-1520
National Category
Cancer and Oncology
Research subject
Medical Radiation Physics
Identifiers
URN: urn:nbn:se:su:diva-158198DOI: 10.1080/0284186X.2018.1473636ISI: 000451615600013Scopus ID: 2-s2.0-85047265665OAI: oai:DiVA.org:su-158198DiVA, id: diva2:1234273
Available from: 2018-07-23 Created: 2018-07-23 Last updated: 2019-09-18Bibliographically approved
In thesis
1. Contouring & planning variability in stereotactic radiosurgery: How to assess and address the weakest link in stereotactic radiosurgery?
Open this publication in new window or tab >>Contouring & planning variability in stereotactic radiosurgery: How to assess and address the weakest link in stereotactic radiosurgery?
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of stereotactic radiosurgery (SRS) employing one or a few fractions of high doses of radiation has continuously increased due to the technical development in dose delivery and morphological and functional imaging. As the target volume in SRS is usually defined without margins, the treatment success critically depends on accurate definition and contouring of the target volume and organs at risk (OARs) which are commonly situated in the proximity of the target making their precise delineation particularly important in order to limit possible normal tissue complications. Subsequent treatment planning is reliant on these volumes, which makes the accurate contouring a requisite to high quality treatments. 

The purpose of this work was to evaluate the current degree of variability for target and OAR contouring and to establish methods for analysing multi-observer data regarding structure delineation variability. Furthermore, this was set in a broader picture including the importance of contouring studies, the clinical implications of contouring errors and the possible mitigation of the variability in contouring by robust treatment planning.

A multi-centre target and OAR contouring study was initiated. Four complex and six common cases to be treated with SRS were selected and subsequently distributed to centres around the world performing Gamma Knife® radiosurgery for delineation and treatment planning. The resulting treatment plans and the corresponding delineated structures were collected and analysed.

Results showed a very high variability in contouring for the four complex radiosurgery targets. Similar results indicating high variability in delineating the common targets and OARs were also reported. This emphasised the need of continuous work towards consistent and standardized SRS treatments. Consequently, the results of the OAR analysis were incorporated in an effort to standardize stereotactic radiosurgery (SRS). Variations in treatment planning were as well analysed for several of the indications included in the initial study on contour delineation and the results showed a high variability in planned doses including several plans presenting large volumes of the brain receiving a higher dose than 12 Gy, indicating an elevated risk of normal tissue complications.

The results of the contouring work were, as a last step of this thesis, used as input for a robust treatment planning approach considering the variability in target delineation. The very preliminary results indicate the feasibility of the probabilistic approach and the potential of robust treatment planning to account for uncertainties in target extent and location.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2019. p. 86
Keywords
stereotactic radiosurgery, contouring variability, robust treatment planning
National Category
Other Physics Topics
Research subject
Medical Radiation Physics
Identifiers
urn:nbn:se:su:diva-173275 (URN)978-91-7797-785-8 (ISBN)978-91-7797-786-5 (ISBN)
Public defence
2019-11-01, CCK lecture hall, building R8, Karolinska University Hospital Solna, Solna, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Manuscript.

Available from: 2019-10-09 Created: 2019-09-18 Last updated: 2020-05-19Bibliographically approved

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