Multicenter End-to-End Evaluation of Single-Isocenter Multitarget Stereotactic Radiosurgery Approaches: Accuracy and Plan Quality

PURPOSE: We conducted a multicenter study on single-isocenter multitarget stereotactic radiosurgery to dosimetrically assess end-to-end test results and identify approaches and techniques influencing spatial accuracy and treatment plan quality. METHODS AND MATERIALS: An anthropomorphic head phantom with radiochromic film and polymer gel inserts was used with a reference structure set of 5 brain metastases. End-to-end tests were performed on-site at 23 centers in Germany, Austria, and Switzerland, each following its own single-isocenter multitarget stereotactic radiosurgery protocol. Spatial accuracy was quantified by comparing planned and measured prescription isodose-volume centroids. Plan quality was assessed from treatment planning system calculations using the Paddick gradient index (GI) and Paddick conformity index. Statistical analyses, including a generalized linear model, correlated results with protocol parameters to identify favorable systems and techniques. RESULTS: = 0.6 ± 0.2 mm versus 1.1 ± 0.3 mm. Mean GI was 6.7 ± 3.3. Automated planning (AP) tools achieved significantly lower GI (4.9 ± 0.7) than conventional planning (8.1 ± 3.8, P = .015). Mean Paddick conformity index was 0.75 ± 0.17, with AP significantly improving conformity (0.83 ± 0.07 vs 0.68 ± 0.19; P = .028) and reducing variability in both indices. Target-to-isocenter distance had no significant influence on spatial accuracy, GI, or Paddick conformity index. CONCLUSIONS: Spatial accuracy in a static phantom was primarily determined by ICC and less by specific delivery infrastructure or techniques, emphasizing the importance of a precise imaging isocenter calibration. AP tools significantly improved and standardized treatment plan quality across centers.

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Journal
International Journal of Radiation Oncology*Biology*Physics
Published
2026-04-01
DOI
https://doi.org/10.1016/j.ijrobp.2026.03.055
Primary Topic
Advanced Radiotherapy Techniques
Type
article
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article

Multicenter End-to-End Evaluation of Single-Isocenter Multitarget Stereotactic Radiosurgery Approaches: Accuracy and Plan Quality

Julian Roers, Márcia Regina Machein, Tino Streller, Christos Moustakis et al.
International Journal of Radiation Oncology*Biology*Physics
Advanced Radiotherapy Techniques
article

Multicenter End-to-End Evaluation of Single-Isocenter Multitarget Stereotactic Radiosurgery Approaches: Accuracy and Plan Quality

Julian Roers, Márcia Regina Machein, Tino Streller, Christos Moustakis, M. Priegnitz, Michael Judge, Daniela Schmitt, Rocco Weigel, Melanie Grehn, Michael Reiner, Janett Köhn, A. Runz, Bastian Bathen, Simon Howitz, Benedikt Thomann, Maximilian Grohmann, Ilinca Popp, Matthias Walke, Ute Ludwig, Ilias Sachpazidis, Tobias Fechter, Jürgen Beck, Thomas R. Konrad, Wolfgang W. Baus, Christian P. Karger, Paul Käthner, Maya Shariff, Nils Wegner, Michelle Grahle, Prof Anca-Ligia Grosu, Christian Ziemann, Johannes Fischer, Michael Bock, Jens Fleckenstein, Oliver Blanck, Dimos Baltas, Evangelos Pappas, Heiko Karle
article en

Abstract

PURPOSE: We conducted a multicenter study on single-isocenter multitarget stereotactic radiosurgery to dosimetrically assess end-to-end test results and identify approaches and techniques influencing spatial accuracy and treatment plan quality. METHODS AND MATERIALS: An anthropomorphic head phantom with radiochromic film and polymer gel inserts was used with a reference structure set of 5 brain metastases. End-to-end tests were performed on-site at 23 centers in Germany, Austria, and Switzerland, each following its own single-isocenter multitarget stereotactic radiosurgery protocol. Spatial accuracy was quantified by comparing planned and measured prescription isodose-volume centroids. Plan quality was assessed from treatment planning system calculations using the Paddick gradient index (GI) and Paddick conformity index. Statistical analyses, including a generalized linear model, correlated results with protocol parameters to identify favorable systems and techniques. RESULTS: = 0.6 ± 0.2 mm versus 1.1 ± 0.3 mm. Mean GI was 6.7 ± 3.3. Automated planning (AP) tools achieved significantly lower GI (4.9 ± 0.7) than conventional planning (8.1 ± 3.8, P = .015). Mean Paddick conformity index was 0.75 ± 0.17, with AP significantly improving conformity (0.83 ± 0.07 vs 0.68 ± 0.19; P = .028) and reducing variability in both indices. Target-to-isocenter distance had no significant influence on spatial accuracy, GI, or Paddick conformity index. CONCLUSIONS: Spatial accuracy in a static phantom was primarily determined by ICC and less by specific delivery infrastructure or techniques, emphasizing the importance of a precise imaging isocenter calibration. AP tools significantly improved and standardized treatment plan quality across centers.

International Journal of Radiation Oncology*Biology*Physics
Goethe University Frankfurt (DE), Universität Hamburg (DE), University of Freiburg (DE), University of Lucerne (CH), German Cancer Research Center (DE), University of Cologne (DE), Johannes Gutenberg University Mainz (DE), Heidelberg University (DE), University of Münster (DE), University Hospital Bonn (DE), University Medical Center Freiburg (DE), University Hospital Heidelberg (DE), LMU Klinikum (DE), Städtisches Klinikum Dresden (DE), University Medical Center of the Johannes Gutenberg University Mainz (DE), University of West Attica (GR), SRH Wald-Klinikum Gera (DE), Graz University Hospital (AT), University Medical Center Hamburg-Eppendorf (DE), National Center for Tumor Diseases (DE), University Hospital Schleswig-Holstein (DE), Universitätsmedizin Göttingen (DE), Tirol Kliniken (AT), University Hospital Leipzig (DE), Universitätsklinikum Würzburg (DE), University Hospital Frankfurt (DE), University Hospital Magdeburg (DE), Medizinische Universität Lausitz - Carl Thiem (DE), Comprehensive Cancer Center Erlangen (DE), University Hospital Cologne (DE), University Medical Centre Mannheim (DE), Klinikum Stuttgart (DE), Ludwig-Maximilians-Universität München (DE), University of Lübeck (DE)
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Advanced Radiotherapy Techniques
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