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Oral Session - Motion Management
10:00am - 10:20am
Collision avoidance trajectories for on-line trajectory optimization in C-arm CBCT
1Austrian Center for Medical Innovation and Technology, Wiener Neustadt, Austria; 2Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Austria; 3Institute of Nuclear Medicine, University College London; 4Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany; 5Institute of Diagnostic and Interventional Radiology and Nuclear Medicine, Landesklinikum Wiener Neustadt, Austria
Kinematic constraints due to the additional medical equipment or patient size are common while acquiring C-arm cone beam computed tomography (CBCT). In a previous paper, we proposed a framework to develop patient-specific collision-free trajectories for the scenarios where circular CBCT is not possible. However, the proposed method required kinematic constraints to be known beforehand. As collisions are mainly unpredictable in the operation theater, a real-time trajectory optimization is of great clinical importance. In this study, we introduce a new search strategy which has the potential to optimize trajectories on-the-fly. We propose an optimization procedure which identifies trajectories with the highest information to reconstruct a volume of interest by means of maximizing an objective function; then a local search is consequently performed around the best selected candidates and better trajectory solutions are investigated. The overall time required for the whole optimization process was around three to four minutes using one GPU.
10:20am - 10:40am
Reference-Free, Learning-Based Image Similarity : Application to Motion Compensation in CBCT
1Johns Hopkins University, United States of America; 2Siemens Healthineers, Germany
Conventional CBCT autofocus metrics are agnostic to the realistic presentation of anatomical structures in the image and can yield unrealistic solutions. Image structural similarity metrics (e.g., visual information fidelity, VIF) combine measures of image quality and structural similarity to a reference image, offering a potentially ideal basis for autofocus metrics. However, matched motion-free reference images are usually not available. In this work, we propose a reference-free, learning-based image similarity metric obtained using a deep neural network (denoted DL-VIF). A convolutional neural network was trained on simulated motion-corrupted CBCT data to extract features associated with the structural components contributing to VIF. The DL-VIF showed a good correlation with conventional VIF. When DL-VIF was incorporated in an autofocus motion compensation framework, and its performance was compared against a conventional metric (gradient entropy). This work is an important step toward reliable motion compensation in scenarios of complex soft-tissue deformable motion in CBCT.
10:40am - 11:00am
DeepSLM: Image Registration Aware of Sliding Interfaces for Motion-Compensated Reconstruction - FULLY3D 2021 AWARD NOMINEE
1German Cancer Research Center, Germany; 2Varian Medical Systems, Switzerland; 3Varian Medical Systems, CA, USA
A common deep convolutional neural network architecture for deformable image registration is adapted to fit the needs of anatomical consistency for motion estimation in motion-compensated reconstruction. We introduce a sliding interface motion constraint to decompose the motion into perpendicular and tangential components in the vicinity of organ interfaces. Three separation schemes are evaluated. The results for the proposed approach, referred to as DeepSLM, show comprehensive motion adaption at the lung border for unseen test data. During inference, no additional input is needed to enable sliding lung motion registration. DeepSLM improves the registration quality and is able to learn anatomical features of the sliding lung border. The network is the basis for future investigations in motion-compensated reconstruction with deep learning techniques.
11:00am - 11:20am
Prior-aided Volume of Interest CBCT Image Reconstruction - FULLY3D 2021 AWARD WINNER
1Institute for Medical Engineering and Research Campus STIMULATE, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany; 2Department of Biomedical Magnetic Resonance and Research Campus STIMULATE, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany
Typical CBCT acquisition protocols require the user to acquire two orthogonal fluoroscopic images for the purpose of positioning the patient ideally for the following complete acquisition. Since these fluoroscopic positioning images are fairly low-dose, they are typically not truncated even for volume of interest imaging acquisitions, except in the case of a too small detector. Yet, they share the positioning of the CBCT acquisition succeeding them and can therefore provide additional information to the reconstruction from truncated projections.
11:20am - 11:40am
Data-driven motion compensated SPECT reconstruction for liver radioembolization
1Kitware SAS, France; 2Univ.Lyon, INSA-Lyon, Universit\'e Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, F-69373, Lyon, France.
Breathing motion is a major issue for quantitation as it leads to misestimation of the tumor activity in the SPECT images. We developed a data-driven motion compensated SPECT reconstruction to account for respiratory motion.
A respiratory signal was extracted from SPECT list-mode data with the Laplacian Eigenmaps algorithm and used to sort the projections into temporal bins of fixed phase width. A 2D affine motion was then estimated between phases. The transformation parameters were used to re-bin the list-mode data into one set of compensated projections that was then used to reconstruct a 3D motion-compensated SPECT image using all available events of the list-mode data.
The method was evaluated on simulated and real liver radioembolization SPECT acquisitions, and compared to a respiratory-gated reconstruction. The motion-compensated reconstruction allowed to retrieve larger activity in the tumors compared to a conventional 3D SPECT reconstruction and with a better contrast-to-noise ratio than gated reconstruction.
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