Stefanie Ehrbar1, Rosalind Perrin2, Marta Peroni2, Kinga Bernatowicz2, Thomas Parkel3, Izabela Pytko4, Stephan Klöck4, Matthias Guckenberger4, Stephanie Tanadini-Lang4, Damien Charles Weber5, Antony Lomax6. 1. Department of Radiation Oncology, University Hospital Zurich (USZ), Switzerland; University of Zurich, Switzerland. Electronic address: stefanie.ehrbar@usz.ch. 2. Center for Proton Therapy, Paul Scherrer Institute (PSI), Switzerland. 3. Innovative Design, Centre Suisse d'Electronique et de Microtechnique (CSEM) S. A., Switzerland. 4. Department of Radiation Oncology, University Hospital Zurich (USZ), Switzerland; University of Zurich, Switzerland. 5. University of Zurich, Switzerland; Center for Proton Therapy, Paul Scherrer Institute (PSI), Switzerland. 6. Center for Proton Therapy, Paul Scherrer Institute (PSI), Switzerland; Swiss Federal Institute of Technology in Zurich (ETHZ), Switzerland.
Abstract
BACKGROUND AND PURPOSE: The objective of this study was to compare the latest respiratory motion-management strategies, namely the internal-target-volume (ITV) concept, the mid-ventilation (MidV) principle, respiratory gating and dynamic couch tracking. MATERIALS AND METHODS: An anthropomorphic, deformable and dynamic lung phantom was used for the dosimetric validation of these techniques. Stereotactic treatments were adapted to match the techniques and five distinct respiration patterns, and delivered to the phantom while radiographic film measurements were taken inside the tumor. To report on tumor coverage, these dose distributions were used to calculate mean doses (Dmean), changes in homogeneity indices (ΔH2-98), gamma agreement, and areas covered by the planned minimum dose (A>Dmin). RESULTS: All techniques achieved good tumor coverage (A>Dmin>99.0%) and minor changes in Dmean (±3.2%). Gating and tracking strategies showed superior results in gamma agreement and ΔH2-98 compared to ITV and MidV concepts, which seem to be more influenced by the interplay and the gradient effect. For lung, heart and spinal cord, significant dose differences between the four techniques were found (p<0.05), with lowest doses for gating and tracking strategies. CONCLUSION: Active motion-management techniques, such as gating or tracking, showed superior tumor dose coverage and better organ dose sparing than the passive techniques based on tumor margins. Copyright Â
BACKGROUND AND PURPOSE: The objective of this study was to compare the latest respiratory motion-management strategies, namely the internal-target-volume (ITV) concept, the mid-ventilation (MidV) principle, respiratory gating and dynamic couch tracking. MATERIALS AND METHODS: An anthropomorphic, deformable and dynamic lung phantom was used for the dosimetric validation of these techniques. Stereotactic treatments were adapted to match the techniques and five distinct respiration patterns, and delivered to the phantom while radiographic film measurements were taken inside the tumor. To report on tumor coverage, these dose distributions were used to calculate mean doses (Dmean), changes in homogeneity indices (ΔH2-98), gamma agreement, and areas covered by the planned minimum dose (A>Dmin). RESULTS: All techniques achieved good tumor coverage (A>Dmin>99.0%) and minor changes in Dmean (±3.2%). Gating and tracking strategies showed superior results in gamma agreement and ΔH2-98 compared to ITV and MidV concepts, which seem to be more influenced by the interplay and the gradient effect. For lung, heart and spinal cord, significant dose differences between the four techniques were found (p<0.05), with lowest doses for gating and tracking strategies. CONCLUSION: Active motion-management techniques, such as gating or tracking, showed superior tumor dose coverage and better organ dose sparing than the passive techniques based on tumor margins. Copyright Â
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