Abstract
Background
The present work aimed to analyze the feasibility of a shuttle-based MRI-guided radiation therapy (MRgRT) in the treatment of pelvic malignancies.
Patients and methods
20 patients with pelvic malignancies were included in this prospective feasibility analysis. Patients underwent daily MRI in treatment position prior to radiotherapy at the German Cancer Research Center. Positional inaccuracies, time and patient compliance were assessed for the application of off-line MRgRT.
Results
In 78% of applied radiation fractions, MR imaging for position verification could be performed without problems. Additionally, treatment-related side effects and reduced patient compliance were only responsible for omission of MRI in 9% of radiation fractions. The study workflow took a median time of 61 min (range 47–99 min); duration for radiotherapy alone was 13 min (range 7–26 min). Patient positioning, MR imaging and CT imaging including patient repositioning and the shuttle transfer required median times of 10 min (range 7–14 min), 26 min (range 15–60 min), 5 min (range 3–8 min) and 8 min (range 2–36 min), respectively.
To assess feasibility of shuttle-based MRgRT, the reference point coordinates for the x, y and z axis were determined for the MR images and CT obtained prior to the first treatment fraction and correlated with the coordinates of the planning CT. In our dataset, the median positional difference between MR imaging and CT-based imaging based on fiducial matching between MR and CT imaging was equal to or less than 2 mm in all spatial directions. The limited space in the MR scanner influenced patient selection, as the bore of the scanner had to accommodate the immobilization device and the constructed stereotactic frame. Therefore, obese, extremely muscular or very tall patients could not be included in this trial in addition to patients for whom exposure to MRI was generally judged inappropriate.
Conclusion
This trial demonstrated for the first time the feasibility and patient compliance of a shuttle-based off-line approach to MRgRT of pelvic malignancies.
Zusammenfassung
Hintergrund
Diese Arbeit analysiert die Machbarkeit einer MR-geführten Radiotherapie (MRgRT) im Beckenbereich mittels Shuttlesystem.
Patienten und Methoden
20 Patienten mit Tumorerkrankungen im Beckenbereich wurden in diese prospektive Machbarkeitsstudie eingeschlossen. Alle Patienten erhielten am Deutschen Krebsforschungszentrum Heidelberg jeweils vor Bestrahlung eine tägliche MRT-Bildgebung in Behandlungsposition. Lageungenauigkeiten, Zeitaufwand und Patientenakzeptanz dieses Offline-MRgRT-Ansatzes wurden erfasst.
Ergebnisse
Bei insgesamt 78 % der Bestrahlungsfraktionen konnte eine MRT-Bildgebung zur Lageverifikation der Patienten problemlos durchgeführt werden. Nur bei 9 % der Bestrahlungsfraktionen führten behandlungsbedingte Nebenwirkungen und eingeschränkte Patientenakzeptanz zum Ausfall der MRT-Scans. Der Zeitaufwand für diesen Offline-MRgRT-Ansatz betrug im Median 61 min (Spanne 47–99 min), davon 13 min für die Bestrahlung (Spanne 7–26 min). Patientenlagerung, MRT-Bildgebung, Cone-Beam-CT-Bildgebung und Transfer beanspruchten nacheinander im Median 10 min (Spanne 7–14 min), 26 min (Spanne 15–60 min), 5 min (Spanne 3–8 min) und 8 min (Spanne 2–36 min). Um die Anwendbarkeit der shuttlebasierten MRgRT zu überprüfen, wurden die Koordinaten des Referenzpunkts auf der MRT- und CT-Bildgebung zu Beginn der Radiotherapie erfasst und mit den Koordinaten der Planungs-CT korreliert. In dieser Studie war die nach Korrelation der Positionsmarker gemessene mediane Lageabweichung zwischen MRT- und Cone-Beam-CT-Bildgebung in allen Raumrichtungen maximal 2 mm. Die Platzvorgaben des MRT-Scanners beeinflussten in dieser Studie die Patientenauswahl dadurch, dass die „Gantry“ sowohl die Immobilisationshilfe als auch den stereotaktischen Rahmen fassen musste. Dadurch konnten adipöse, sehr muskulöse oder sehr große Patienten sowie Patienten mit Kontraindikationen für eine MRT-Untersuchung nicht in diese Studie eingeschlossen werden.
Schlussfolgerung
Diese Studie zeigte zum ersten Mal die Machbarkeit und Patientenakzeptanz eines shuttlebasierten Offline-Konzepts für die MRgRT pelviner Tumore.
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Acknowledgements
We acknowledge the help of Rolf Bendl and Paul Mercea regarding the development of the hardware required for this trial. We also thank Annette Miltner, Marion Bachmann, Elisabeth Rittinghausen, Armin Runz and René Hertel for their excellent technical support.
Funding
This project was in part funded by a research grant of the German Federal Ministry of Education and Research (BMBF).
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T. Bostel, A. Pfaffenberger, S. Delorme, C. Dreher, G. Echner, P. Haering, C. Lang, M. Splinter, F. Laun, M. Müller, O. Jäkel, J. Debus, P.E. Huber, F. Sterzing and N.H. Nicolay declare that they have no competing interests.
Ethical standards
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.
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Bostel, T., Pfaffenberger, A., Delorme, S. et al. Prospective feasibility analysis of a novel off-line approach for MR-guided radiotherapy. Strahlenther Onkol 194, 425–434 (2018). https://doi.org/10.1007/s00066-017-1258-y
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DOI: https://doi.org/10.1007/s00066-017-1258-y