Multi-centre calibration of an adaptive thresholding method for PET-based delineation of tumour volumes in radiotherapy planning of lung cancer

A. Schaefer; U. Nestle; S. Kremp; D. Hellwig; A. Grgic; H. G. Buchholz; W. Mischke; C. Gromoll; P. Dennert; M. Plotkin; S. Senftleben; D. Thorwarth; M. Tosch; A. Wahl; H. Wengenmair; C. Rübe; C.-M. Kirsch

doi:10.3413/Nukmed-0452-11-12

Nuklearmedizin - NuclearMedicine, Inhaltsverzeichnis

Nuklearmedizin 2012; 51(03): 101-110
DOI: 10.3413/Nukmed-0452-11-12

Original article

Schattauer GmbH

Multi-centre calibration of an adaptive thresholding method for PET-based delineation of tumour volumes in radiotherapy planning of lung cancer

Multizentrische Kalibrierung eines adaptiven Schwellwertverfahrens zur PET-basierten Volumen konturierung in der Bestrahlungsplanung des Lungenkarzinoms

A. Schaefer

¹Department of Nuclear Medicine, Saarland University Medical Center, Homburg, Germany

,

U. Nestle

³Department of Radiotherapy, University Medical Center Freiburg

,

S. Kremp

²Department of Radiotherapy, Saarland University Medical Center, Homburg, Germany

,

D. Hellwig

¹Department of Nuclear Medicine, Saarland University Medical Center, Homburg, Germany

,

A. Grgic

¹Department of Nuclear Medicine, Saarland University Medical Center, Homburg, Germany

,

H. G. Buchholz

⁴Department of Nuclear Medicine, Johannes Gutenberg University Medical Center, Mainz, Germany

,

W. Mischke

⁵Department of Nuclear Medicine, Helios clinics, Berlin, Germany

,

C. Gromoll

⁶Department of Medical Physics, Marienhospital- Medical Center, Stuttgart, Germany

,

P. Dennert

⁷Department of Radiotherapy, Friedrich-Ebert-Medical Center, Neumünster, Germany

,

M. Plotkin

⁸Department of Nuclear Medicine, Charité University Medical Center, Berlin, Germany

,

S. Senftleben

⁹Department of Nuclear Medicine, PET-Center, Bad Berka, Germany

,

D. Thorwarth

¹⁰Section for Biomedical Physics, University Hospital for Radiation Oncology, Eberhard-Karls University, Tübingen, Germany

,

M. Tosch

¹¹Department of Nuclear Medicine, Maria-Hilf-Medical Center, Mönchengladbach, Germany

,

A. Wahl

¹²Department of Nuclear Medicine, PET/CT-Center, Hamburg, Germany

,

H. Wengenmair

¹³Department of Medical Physics, Medical Center, Augsburg, Germany

,

C. Rübe

²Department of Radiotherapy, Saarland University Medical Center, Homburg, Germany

,

C.-M. Kirsch

¹Department of Nuclear Medicine, Saarland University Medical Center, Homburg, Germany

› Institutsangaben

Abstract

Summary

Purpose: To evaluate the calibration of an adaptive thresholding algorithm (contrastoriented algorithm) for FDG PET-based delineation of tumour volumes in eleven centres with respect to scanner types and image data processing by phantom measurements. Methods: A cylindrical phantom with spheres of different diameters was filled with FDG realizing different signal-to-background ratios and scanned using 5 Siemens Biograph PET/CT scanners, 5 Philips Gemini PET/CT scanners, and one Siemens ECAT-ART PET scanner. All scans were analysed by the contrast-oriented algorithm implemented in two different software packages. For each site, the threshold SUVs of all spheres best matching the known sphere volumes were determined. Calibration parameters a and b were calculated for each combination of scanner and image-analysis software package. In addition, “scanner-typespecific” calibration curves were determined from all values obtained for each combination of scanner type and software package. Both kinds of calibration curves were used for volume delineation of the spheres. Results: Only minor differences in calibration parameters were observed for scanners of the same type (Δa ≤ 4%, Δb ≤ 14%) provided that identical imaging protocols were used whereas significant differences were found comparing calibration parameters of the ART scanner with those of scanners of different type (Δa ≤ 60%, Δb ≤ 54%). After calibration, for all scanners investigated the calculated SUV thresholds for auto-contouring did not differ significantly (all p > 0.58). The resulting sphere volumes deviated by less than –7% to +8% from the true values. Conclusion: After multi-centre calibration the use of the contrast-oriented algorithm for FDG PET-based delineation of tumour volumes in the different centres using different scanner types and specific imaging protocols is feasible.

Zusammenfassung

Ziel: Anhand von Phantommessungen in elf Zentren sollte überprüft werden, ob der kontrast- orientierte Algorithmus zur Volumenkonturierung in der FDG-PET nach Kalibrierung multizentrisch eingesetzt werden kann. Methodik: Phantommessungen eines Zylinderphantoms mit integrierten Glaskugeln verschiedener Durchmesser wurden an fünf Siemens- Biograph-PET/CT-Scannern, fünf Philips- Gemini-PET/CT-Scannern und an einem Siemens-ECAT-ART-PET-Scanner durchge - führt, wobei verschiedene Signal-zu-Hintergrund- Verhältnisse simuliert wurden. Die Auswertung erfolgte unter Anwendung des Kontrast- orientierten Algorithmus in zwei Software- Systemen. In jedem Zentrum wurden die Schwellenwert-SUVs ermittelt, die die wahren Kugelvolumina am besten wiedergaben. Hieraus wurden „zentrumsspezifische“ Werte für die Konstanten a und b der Kalibrierkurven der einzelnen Scanner nach Auswertung in beiden Software-Systemen bestimmt. Zusätzlich wurden aus allen Messwerten „scannerspezifische“ Kalibrierkurven für jede Kombination aus Scannertyp und Auswertesoftware ermittelt. Beide Arten der Kalibrierung wurden zur Konturierung der Kugelvolumina eingesetzt. Ergebnisse: Unter der Voraussetzung, dass übereinstimmende Akquisitions- und Auswerteprotokolle eingesetzt wurden, unterscheiden sich die Werte der Parameter a und b für Scanner des gleichen Typs nur wenig (Δa ≤ 4%, Δb ≤ 14%). Im Vergleich hierzu wurden für den ARTScanner signifikant unterschiedliche Werte der Parameter a und b beobachtet. Nach Kalibrierung waren die mittels Kontrastorientiertem Algorithmus errechneten SUVSchwellenwerte der verschiedenen Scanner statistisch nicht signifikant unterschiedlich (alle p > 0,58). Die konturierten Kugelvolumina zeigten Abweichungen von den wahren Werten zwischen –7% und +8%. Schlussfolgerung: Der Kontrast-orientierte Algorithmus eignet sich nach Kalibrierung der Scanner-Typen einschließlich der Akquisitions- und Auswerteprotokolle gut zur FDG-PET-basierten Zielvolumenkonturierung und ist multizentrisch einsetzbar.

Keywords

Volume delineation - 18F-FDG-PET - lung cancer - GTV definition - multi-centre trial - calibration

Schlüsselwörter

Volumenbestimmung - 18F-FDG-PET - Lungenkrebs - GTV-Definition - Multicenter-Studie - Kalibrierung

Volltext

Referenzen

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