Geometric Verification of Dynamic Wave Arc Delivery With the Vero System Using Orthogonal X-ray Fluoroscopic Imaging

Manuela Burghelea; Dirk Verellen; Kenneth Poels; Thierry Gevaert; Tom Depuydt; Koen Tournel; Cecilia Hung; Viorica Simon; Masahiro Hiraoka; Mark de Ridder

doi:10.1016/j.ijrobp.2015.02.053

Geometric Verification of Dynamic Wave Arc Delivery With the Vero System Using Orthogonal X-ray Fluoroscopic Imaging

Int J Radiat Oncol Biol Phys. 2015 Jul 15;92(4):754-61. doi: 10.1016/j.ijrobp.2015.02.053. Epub 2015 Mar 5.

Authors

Affiliations

¹ Department of Radiotherapy, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels, Belgium; Faculty of Physics, Babes Bolyai University, Cluj-Napoca, Romania; R&D Radiosurgery, BrainLAB AG, Munich, Germany. Electronic address: manuela.buleteanu@yahoo.com.
² Department of Radiotherapy, Universitair Ziekenhuis Brussel, Vrije Universiteit Brussel, Brussels, Belgium.
³ Department of Radiation Oncology, University Hospitals Leuven, Leuven, Belgium.
⁴ R&D Radiosurgery, BrainLAB AG, Munich, Germany.
⁵ Department of Radiation Oncology and Image-applied Therapy, Kyoto University Graduate School of Medicine, Kyoto, Japan.

PMID: 25962626
DOI: 10.1016/j.ijrobp.2015.02.053

Abstract

Purpose: The purpose of this study was to define an independent verification method based on on-board orthogonal fluoroscopy to determine the geometric accuracy of synchronized gantry-ring (G/R) rotations during dynamic wave arc (DWA) delivery available on the Vero system.

Methods and materials: A verification method for DWA was developed to calculate O-ring-gantry (G/R) positional information from ball-bearing positions retrieved from fluoroscopic images of a cubic phantom acquired during DWA delivery. Different noncoplanar trajectories were generated in order to investigate the influence of path complexity on delivery accuracy. The G/R positions detected from the fluoroscopy images (DetPositions) were benchmarked against the G/R angulations retrieved from the control points (CP) of the DWA RT plan and the DWA log files recorded by the treatment console during DWA delivery (LogActed). The G/R rotational accuracy was quantified as the mean absolute deviation ± standard deviation. The maximum G/R absolute deviation was calculated as the maximum 3-dimensional distance between the CP and the closest DetPositions.

Results: In the CP versus DetPositions comparison, an overall mean G/R deviation of 0.13°/0.16° ± 0.16°/0.16° was obtained, with a maximum G/R deviation of 0.6°/0.2°. For the LogActed versus DetPositions evaluation, the overall mean deviation was 0.08°/0.15° ± 0.10°/0.10° with a maximum G/R of 0.3°/0.4°. The largest decoupled deviations registered for gantry and ring were 0.6° and 0.4° respectively. No directional dependence was observed between clockwise and counterclockwise rotations. Doubling the dose resulted in a double number of detected points around each CP, and an angular deviation reduction in all cases.

Conclusions: An independent geometric quality assurance approach was developed for DWA delivery verification and was successfully applied on diverse trajectories. Results showed that the Vero system is capable of following complex G/R trajectories with maximum deviations during DWA below 0.6°.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Algorithms
Calibration
Diagnostic Imaging
Equipment Design
Fluoroscopy*
Humans
Phantoms, Imaging*
Radiotherapy, Image-Guided / instrumentation*
Radiotherapy, Image-Guided / methods
Radiotherapy, Intensity-Modulated / instrumentation*
Radiotherapy, Intensity-Modulated / methods
Rotation*
Sensitivity and Specificity