Multiple breath-hold CBCT for online image guided radiotherapy of lung tumors: Simulation with a dynamic phantom and first patient data |
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Authors: | Judit Boda-Heggemann Jens FleckensteinFrank Lohr Hansjörg WertzMohammed Nachit Manuel BlessingDzimitry Stsepankou Iris LöbBeate Küpper Anthony KavanaghVibeke N Hansen Michael BradaFrederik Wenz Helen McNair |
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Institution: | a Department of Radiation Oncology, University Medical Center Mannheim, University of Heidelberg, Mannheim, Germany b Royal Marsden NHS Foundation Trust and Institute of Cancer Research, Radiotherapy Department, Surrey, UK |
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Abstract: | Background and PurposeComputer controlled breath-hold effectively reduces organ motion for image-guided precision radiotherapy of lung tumors. However, the acquisition time of 3D cone-beam-CT (CBCT) exceeds maximum breath-hold times. We have developed an approach enabling online verification using CBCT image acquisition with ABC®-based breath-hold.MethodsPatient CBCT images were acquired with ABC®-based repeat breath-hold. The clinical situation was also simulated with a Motion Phantom. Reconstruction of patient and phantom images with selection of free-breathing and breath-hold projections only was performed.ResultsCBCT-imaging in repeat breath-hold resulted in a precisely spherical appearance of a tumor-mimicking structure in the phantom. A faint “ghost” structure (free-breathing phases) can be clearly discriminated. Mean percentage of patient breath-hold time was 66%. Reconstruction based on free-breathing-only shows blurring of both tumor and diaphragm, reconstruction based on breath-hold projections only resulted in sharp contours of the same structures. From the phantom experiments, a maximal repositioning error of 1 mm in each direction can be estimated.Discussion and ConclusionCBCT during repetitive breath hold provides reliable soft-tissue-based positioning. Fast 3D-imaging during one breath-hold is currently under development and has the potential to accelerate clinical linac-based volume imaging. |
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Keywords: | ABC® Repeat breath hold Cone-beam CT Breath-hold imaging |
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