Program Information
An Algorithm to Extract Motion and Physical Parameters of Mobile Targets Imaged with Cone-Beam CT Using Displacement Vector Fields Calculated by Deformable Image Registration Algorithms
N Alsbou1, S Ahmad2 , I Ali2 , (1) University of Central Oklahoma, Edmond, OK, (2) University of Oklahoma Health Sciences, Oklahoma City, OK
Presentations
TU-C2-GePD-JT-4 (Tuesday, August 1, 2017) 10:00 AM - 10:30 AM Room: Joint Imaging-Therapy ePoster Theater
Purpose: To develop an algorithm that extracts motion and physical parameters of mobile targets from the displacement-vector-field (DVF) calculated by different deformable image registration (DIR) techniques used to register cone-beam CT images (CBCT).
Methods: The algorithm developed in this study uses the DVF distributions calculated by four DIR techniques including Demons, Fast-Demons, Horn-Schunck and Lucas-Kanade from DIRART software. These DIR techniques were used to register CBCT images for a mobile thorax phantom with three targets. The phantom moved with different motion amplitudes (0-20mm) and frequencies (0.125-0.5Hz) using controlled cyclic motion patterns. The predictions of the algorithm were tested by quantitative investigation of the DVF maps obtained from the aforementioned techniques.
Results: Using this algorithm, motion and physical parameters of the mobile targets were extracted from the DVF distributions produced by the DIR techniques used to register CBCT images. The maximal and minimal DVFs were used to extract the motion amplitude of the different mobile targets. The zero-level crossovers in the DFV profiles were used to extract the lengths of the mobile targets in CBCT images. The DVF distributions motion artifacts depended mainly on motion amplitudes and less on motion frequencies and phases in CBCT images. This algorithm worked better with the optical-flow based Horn-Schunck and Lucas-Kanade algorithms which produced more consistent patterns in the DVF distributions compared with the Demons and Fast-Demons.
Conclusion: An algorithm was developed to extract motion and physical parameters from the DVF distributions calculated by different DIR techniques used to register CBCT images. It used the DVF distributions without prior knowledge of mobile target which has potential applications in diagnostic CT imaging and radiotherapy. The determination of motion and physical parameters of the mobile target in CT images provides an approach to calculate accurate volumes and treatment margins for tumors treated with radiotherapy.
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