Per Rugaard Poulsen1, Esben S Worm2, Jørgen B B Petersen3, Cai Grau4, Walther Fledelius2, Morten Høyer4. 1. Department of Oncology, Aarhus University Hospital, Denmark; Institute of Clinical Medicine, Aarhus University, Denmark. Electronic address: per.poulsen@rm.dk. 2. Department of Oncology, Aarhus University Hospital, Denmark; Department of Medical Physics, Aarhus University Hospital, Denmark. 3. Department of Medical Physics, Aarhus University Hospital, Denmark. 4. Department of Oncology, Aarhus University Hospital, Denmark; Institute of Clinical Medicine, Aarhus University, Denmark.
Abstract
PURPOSE: To use intrafraction kilovoltage (kV) imaging during liver stereotactic body radiotherapy (SBRT) delivered by volumetric modulated arc therapy (VMAT) to estimate the intra-treatment target motion and to reconstruct the delivered target dose. METHODS: Six liver SBRT patients with 2-3 implanted gold markers received SBRT in three fractions of 18.75 Gy or 25 Gy. CTV-to-PTV margins of 5 mm in the axial plane and 10 mm in the cranio-caudal directions were applied. A VMAT plan was designed to give minimum target doses of 95% (CTV) and 67% (PTV). At each fraction, the 3D marker trajectory was estimated by fluoroscopic kV imaging throughout treatment delivery and used to reconstruct the actually delivered CTV dose. The reduction in D95 (minimum dose to 95% of the CTV) relative to the planned D95 was calculated. RESULTS: The kV position estimation had mean root-mean-square errors of 0.36 mm and 0.47 mm parallel and perpendicular to the kV imager, respectively. Intrafraction motion caused a mean 3D target position error of 2.9 mm and a mean D95 reduction of 6.0%. The D95 reduction correlated with the mean 3D target position error during a fraction. CONCLUSIONS: Kilovoltage imaging for detailed motion monitoring with dose reconstruction of VMAT-based liver SBRT was demonstrated for the first time showing large dosimetric impact of intrafraction tumor motion.
PURPOSE: To use intrafraction kilovoltage (kV) imaging during liver stereotactic body radiotherapy (SBRT) delivered by volumetric modulated arc therapy (VMAT) to estimate the intra-treatment target motion and to reconstruct the delivered target dose. METHODS: Six liver SBRT patients with 2-3 implanted gold markers received SBRT in three fractions of 18.75 Gy or 25 Gy. CTV-to-PTV margins of 5 mm in the axial plane and 10 mm in the cranio-caudal directions were applied. A VMAT plan was designed to give minimum target doses of 95% (CTV) and 67% (PTV). At each fraction, the 3D marker trajectory was estimated by fluoroscopic kV imaging throughout treatment delivery and used to reconstruct the actually delivered CTV dose. The reduction in D95 (minimum dose to 95% of the CTV) relative to the planned D95 was calculated. RESULTS: The kV position estimation had mean root-mean-square errors of 0.36 mm and 0.47 mm parallel and perpendicular to the kV imager, respectively. Intrafraction motion caused a mean 3D target position error of 2.9 mm and a mean D95 reduction of 6.0%. The D95 reduction correlated with the mean 3D target position error during a fraction. CONCLUSIONS: Kilovoltage imaging for detailed motion monitoring with dose reconstruction of VMAT-based liver SBRT was demonstrated for the first time showing large dosimetric impact of intrafraction tumor motion.
Authors: Thomas Woolcot; Evanthia Kousi; Emma Wells; Katharine Aitken; Helen Taylor; Maria A Schmidt Journal: Phys Imaging Radiat Oncol Date: 2018-09-06
Authors: Fabian Weykamp; Philipp Hoegen; Sebastian Klüter; C Katharina Spindeldreier; Laila König; Katharina Seidensaal; Sebastian Regnery; Jakob Liermann; Carolin Rippke; Stefan A Koerber; Carolin Buchele; Jürgen Debus; Juliane Hörner-Rieber Journal: Front Oncol Date: 2021-06-09 Impact factor: 6.244