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

Thomann B, Fechter T, Fischer J, Runz A, Ludwig U, Sachpazidis I, Blanck O, Roers J, Grehn M, Grohmann M, Ziemann C, Judge M, Baus W, Grahle M, Walke M, Bathen B, Köhn J, Käthner P, Shariff M, Wegner N, Fleckenstein J, Karle H, Streller T, Howitz S, Priegnitz M, Weigel R, Konrad T, Schmitt D, Beck J, Machein M, Popp I, Reiner M, Moustakis C, Karger CP, Pappas E, Grosu AL, Bock M, Baltas D (2026)

Publication Type: Journal article

Publication year: 2026

Journal

DOI: 10.1016/j.ijrobp.2026.03.055

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: The mean spatial offset between measured and calculated prescription isodose centroids across all centers and targets was 0.9 ± 0.4(1σ) mm. Offsets above 1 mm were observed in 33% of centers. Better imaging-to-radiation isocenter consistency (ICC) yielded significantly higher accuracy (P = .002): dICC<median = 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.

Authors with CRIS profile

Involved external institutions

Universitätsklinikum Frankfurt am Main (KGU) Germany (DE) Albert-Ludwigs-Universität Freiburg Germany (DE) Universitätsklinikum Freiburg Germany (DE) Universitätsklinikum Schleswig-Holstein (UKSH) Germany (DE) Universitätsklinikum Münster Germany (DE) Universitätsklinikum Hamburg-Eppendorf (UKE) Germany (DE) WEGE Klinik Germany (DE) Städtisches Klinikum Dresden Germany (DE) Universitätsklinikum Würzburg Germany (DE) Klinikum Stuttgart Germany (DE) Universitätsklinikum Mannheim / University Medical Centre Mannheim (Universitätsmedizin Mannheim) Germany (DE) Universitätsmedizin der Johannes Gutenberg-Universität Mainz Germany (DE) Luzerner Kantonsspital (LUKS) Switzerland (CH) SRH Wald-Klinikum Gera Germany (DE) Medizinische Universität Lausitz – Carl Thiem Germany (DE) Steiermärkische Krankenanstaltengesellschaft m. b. H. LKH-Univ. Klinikum Graz Austria (AT) Universitätsklinikum Göttingen Germany (DE) Klinikum der Universität München (LMU Klinikum) Germany (DE) Universitätsklinikum Leipzig Germany (DE) Deutsches Krebsforschungszentrum (DKFZ) Germany (DE) University of West Attica (UNIWA) / Πανεπιστήμιο Δυτικής Αττικής Greece (GR)

How to cite

APA:

Thomann, B., Fechter, T., Fischer, J., Runz, A., Ludwig, U., Sachpazidis, I.,... Baltas, D. (2026). Multicenter End-to-End Evaluation of Single-Isocenter Multitarget Stereotactic Radiosurgery Approaches: Accuracy and Plan Quality. International Journal of Radiation Oncology Biology Physics. https://doi.org/10.1016/j.ijrobp.2026.03.055

MLA:

Thomann, Benedikt, et al. "Multicenter End-to-End Evaluation of Single-Isocenter Multitarget Stereotactic Radiosurgery Approaches: Accuracy and Plan Quality." International Journal of Radiation Oncology Biology Physics (2026).

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