Journal Article

DKFZ-2026-00839

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Multicenter end-to-end evaluation of single-isocenter multitarget stereotactic radiosurgery approaches: accuracy and plan quality.

Thomann, B.DKFZ* ; Fechter, T.DKFZ* ; Fischer, J. ; Runz, A.DKFZ* ; Ludwig, U. ; Sachpazidis, I.DKFZ* ; 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.DKFZ* ; Reiner, M. ; Moustakis, C. ; Karger, C. P.DKFZ* ; Pappas, E. ; Grosu, A.-L. ; Bock, M. ; Baltas, D.DKFZ*

2026
Elsevier Science Amsterdam [u.a.]

Abstract: We conducted a multicenter study on single-isocenter multitarget stereotactic radiosurgery (SIMT SRS) to dosimetrically assess end-to-end test results and identify approaches and techniques influencing spatial accuracy and treatment plan quality.An anthropomorphic head phantom with radiochromic film and polymer gel inserts was used with a reference structure set of five brain metastases. End-to-end tests were performed on-site at 23 centers in Germany, Austria, and Switzerland, each following its own SIMT SRS protocol. Spatial accuracy was quantified by comparing planned and measured prescription isodose volume centroids. Plan quality was assessed from treatment planning system calculations using Paddick gradient index (GI) and conformity index (PCI). Statistical analyses, including a generalized linear model, correlated results with protocol parameters to identify favorable systems and techniques.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 = 0.002): dICC<Median = 0.6 ± 0.2 mm vs. dICC>Median = 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 = 0.015). Mean PCI was 0.75 ± 0.17, with AP significantly improving conformity (0.83 ± 0.07 vs. 0.68 ± 0.19, p = 0.028) and reducing variability in both indices. Target-to-isocenter distance had no significant influence on spatial accuracy, GI or PCI.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.

Keyword(s): Plan quality ; Stereotactic radiosurgery ; end-to-end ; multicenter ; multitarget ; single-isocenter ; treatment accuracy

Note: epub

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Contributing Institute(s):

1. DKTK Koordinierungsstelle Freiburg (FR01)
2. E040 Med. Physik in der Strahlentherapie (E040)

Research Program(s):

1. 315 - Bildgebung und Radioonkologie (POF4-315) (POF4-315)

Appears in the scientific report 2026

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Database coverage:
; BIOSIS Previews ; Biological Abstracts ; Clarivate Analytics Master Journal List ; Current Contents - Clinical Medicine ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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