Multi-institutional study of the variability in target delineation for six targets commonly treated with radiosurgery

Abstract

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.

Acknowledgments

The cooperation of all participants involved in this study is gratefully acknowledged: Department of Stereotactic and Radiation Neurosurgery and Department of Medical Physics at Na Homolce Hospital in Prague, Czech Republic, Ian Paddick MSc and Tim Cox MD at Cromwell Gamma Knife Centre in London, England, Katherine Hunt BEng MSc MIPEM, Ruth Batty MD PhD FRCR, Dan Connolly MD PhD FRCR, John Yianni MD FRCS(SN) and Jeremy Rowe MD MA DM FRCS(SN) of the National Centre for Stereotactic Radiosurgery at Royal Hallamshire Hospital in Sheffield, England, Professor Lijun Ma and Professor Penny Sneed at the UCSF Gamma Knife Center in San Francisco, USA, Taylor McAdam Vell Neuroscience Institute at Washington Hospital in Fremont California, USA, Francisco Li MSc RSO at the Swedish Radiosurgery Center in Seattle, USA, Hyun-Tai Chung PhD at the Department of Neurosurgery Seoul National University College of Medicine in Seoul, Korea, Monique van Prooijen PhD at the Princess Margaret Cancer Centre in Toronto, Canada, Chryssa Paraskevopoulou MSc of Hygeia Hospital in Athens, Greece, Bente Sandvei Skeie MD PhD and Jan Heggdal MSc at the Department of Oncology and Medical Physics at Haukeland University Hospital in Bergen, Norway, David Schlesinger PhD, David Larson MD and Kevin Orcutt MD from the Department of Radiation Oncology at the University of Virginia in Charlottesville Virginia, USA. Technical assistance of Björn Somell at Elekta Instrument AB in Stockholm is also gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support from the Cancer Research Funds of Radiumhemmet is also gratefully acknowledged.