Tobias Gauer1, Thilo Sothmann2,3, Oliver Blanck4,5, Cordula Petersen2, René Werner3. 1. Department of Radiotherapy and Radio-Oncology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany. t.gauer@uke.de. 2. Department of Radiotherapy and Radio-Oncology, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany. 3. Department of Computational Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. 4. Saphir Radiosurgery Center Frankfurt and Güstrow, Güstrow, Germany. 5. Department of Radiation Oncology, University Medical Center of Schleswig-Holstein, Kiel, Germany.
Abstract
BACKGROUND AND PURPOSE: Radiotherapy of extracranial metastases changed from normofractioned 3D CRT to extreme hypofractionated stereotactic treatment using VMAT beam techniques. Random interaction between tumour motion and dynamically changing beam parameters might result in underdosage of the CTV even for an appropriately dimensioned ITV (interplay effect). This study presents a clinical scenario of extreme hypofractionated stereotactic treatment and analyses the impact of interplay effects on CTV dose coverage. METHODS: For a thoracic/abdominal phantom with an integrated high-resolution detector array placed on a 4D motion platform, dual-arc treatment plans with homogenous target coverage were created using a common VMAT technique and delivered in a single fraction. CTV underdosage through interplay effects was investigated by comparing dose measurements with and without tumour motion during plan delivery. RESULTS: Our study agrees with previous works that pointed out insignificant interplay effects on target coverage for very regular tumour motion patterns like simple sinusoidal motion. However, we identified and illustrated scenarios that are likely to result in a clinically relevant CTV underdosage. For tumour motion with abnormal variability, target coverage quantified by the CTV area receiving more than 98% of the prescribed dose decreased to 78% compared to 100% at static dose measurement. CONCLUSION: This study is further proof of considerable influence of interplay effects on VMAT dose delivery in stereotactic radiotherapy. For selected conditions of an exemplary scenario, interplay effects and related motion-induced target underdosage primarily occurred in tumour motion pattern with increased motion variability and VMAT plan delivery using complex MLC dose modulation.
BACKGROUND AND PURPOSE: Radiotherapy of extracranial metastases changed from normofractioned 3D CRT to extreme hypofractionated stereotactic treatment using VMAT beam techniques. Random interaction between tumour motion and dynamically changing beam parameters might result in underdosage of the CTV even for an appropriately dimensioned ITV (interplay effect). This study presents a clinical scenario of extreme hypofractionated stereotactic treatment and analyses the impact of interplay effects on CTV dose coverage. METHODS: For a thoracic/abdominal phantom with an integrated high-resolution detector array placed on a 4D motion platform, dual-arc treatment plans with homogenous target coverage were created using a common VMAT technique and delivered in a single fraction. CTV underdosage through interplay effects was investigated by comparing dose measurements with and without tumour motion during plan delivery. RESULTS: Our study agrees with previous works that pointed out insignificant interplay effects on target coverage for very regular tumour motion patterns like simple sinusoidal motion. However, we identified and illustrated scenarios that are likely to result in a clinically relevant CTV underdosage. For tumour motion with abnormal variability, target coverage quantified by the CTV area receiving more than 98% of the prescribed dose decreased to 78% compared to 100% at static dose measurement. CONCLUSION: This study is further proof of considerable influence of interplay effects on VMAT dose delivery in stereotactic radiotherapy. For selected conditions of an exemplary scenario, interplay effects and related motion-induced target underdosage primarily occurred in tumour motion pattern with increased motion variability and VMAT plan delivery using complex MLC dose modulation.
Authors: Florian Sterzing; Thomas B Brunner; Iris Ernst; Wolfgang W Baus; Burkhard Greve; Klaus Herfarth; Matthias Guckenberger Journal: Strahlenther Onkol Date: 2014-08-05 Impact factor: 3.621
Authors: Oliver Blanck; Laura Masi; Mark K H Chan; Sebastian Adamczyk; Christian Albrecht; Marie-Christin Damme; Britta Loutfi-Krauss; Manfred Alraun; Roman Fehr; Ulla Ramm; Frank-Andre Siebert; Tenzin Sonam Stelljes; Daniela Poppinga; Björn Poppe Journal: Phys Med Date: 2016-05-27 Impact factor: 2.685