Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Variability in target delineation for cavernous sinus meningioma and anaplastic astrocytoma in stereotactic radiosurgery with Leksell Gamma Knife Perfexion
Stockholm University, Faculty of Science, Department of Physics. Karolinska Institutet, Sweden.
Elekta Instrument AB, Sweden.
Elekta Instrument AB, Sweden.
Elekta Instrument AB, Sweden.
Show others and affiliations
2014 (English)In: Acta Neurochirurgica, ISSN 0001-6268, E-ISSN 0942-0940, Vol. 156, no 12, p. 2303-2313Article in journal (Refereed) Published
Abstract [en]

Background: Radiosurgery clinical practice relays on empirical observations and the experience of the practitioners involved in determining and delineating the target and therefore variability in target delineation might be expected for all the radiosurgery approaches, independent of the technique and the equipment used for delivering the treatment. The main aim of this study was to quantify the variability of target delineation for two radiosurgery targets expected to be difficult to delineate. The secondary aim was to investigate the dosimetric implications with respect to the plan conformity. The primary aim of the study has therefore a very general character, not being bound to one specific radiosurgery technique.

Materials and methods: Twenty radiosurgery centers were asked to delineate one cavernous sinus meningioma and one astrocytoma and to plan the treatments for Leksell Gamma Knife Perfexion. The analysis of the delineated targets was based on the calculated 50% agreement volume, AV50. The AV50 was compared to each delineated target by the concordance index and discordance index. The differences in location, size, and shape of the delineated targets were also analyzed using the encompassing volume compared to the common volume, i.e., the AV100, of all delineated structures.

Results: Target delineation led to major differences between the participating centers and therefore the AV50 was small in comparison to each delineated target volume. For meningioma, the AV50 was 5.90 cm3, the AV100 was 2.60 cm3, and the encompassing volume was 13.14 cm3. For astrocytoma, the AV50 was 2.06 cm3 while the AV100 was extremely small, only 0.05 cm3, and the encompassing volume was 43.27 cm3. These variations translate into corresponding discrepancies in plan conformity.

Conclusions: Significant differences in shape, size, and location between the targets included in this study were identified and therefore the clinical implications of these differences should be further investigated.

Place, publisher, year, edition, pages
2014. Vol. 156, no 12, p. 2303-2313
Keywords [en]
Leksell Gamma Knife Perfexion; Gamma Knife radiosurgery; Radiosurgery; Target delineation; Astrocytoma; Meningioma; Inter-observer variability
National Category
Cancer and Oncology
Research subject
Medical Radiation Physics
Identifiers
URN: urn:nbn:se:su:diva-107221DOI: 10.1007/s00701-014-2235-1ISI: 000345097700012OAI: oai:DiVA.org:su-107221DiVA, id: diva2:744115
Available from: 2014-09-06 Created: 2014-09-06 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: 2019-10-09Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full text

Search in DiVA

By author/editor
Sandström, HelenaJokura, HidefumiToma-Dasu, Iuliana
By organisation
Department of Physics
In the same journal
Acta Neurochirurgica
Cancer and Oncology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 78 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf