196 research outputs found
Temporal Diffeomorphic Free-Form Deformation for Strain Quantification in 3D-US Images
International audienceThis paper presents a new diffeomorphic temporal registration algorithm and its application to motion and strain quantification from a temporal sequence of 3D images. The displacement field is computed by forward eulerian integration of a non-stationary velocity field. The originality of our approach resides in enforcing time consistency by representing the velocity field as a sum of continuous spatiotemporal B-Spline kernels. The accuracy of the developed diffeomorphic technique was first compared to a simple pairwise strategy on synthetic US images with known ground truth motion and with several noise levels, being the proposed algorithm more robust to noise than the pairwise case. Our algorithm was then applied to a database of cardiac 3D+t Ultrasound (US) images of the left ventricle acquired from height healthy volunteers and three Cardiac Resynchronization Therapy (CRT) patients. On healthy cases, the measured regional strain curves provided uniform strain patterns over all myocardial segments in accordance with clinical literature. On CRT patients, the obtained normalization of the strain pattern after CRT agreed with clinical outcome for the three cases
Temporal diffeomorphic Free Form Deformation (TDFFD) applied to motion and deformation quantification of tagged MRI sequences
International audienceThis paper presents strain quantification results obtained from the Tagged Magnetic Resonance Imaging (TMRI) sequences acquired for the 1 st cardiac Motion Analysis Challenge (cMAC). We applied the Temporal Diffeomorphic Free Form Deformation (TDFFD) algorithm to the phantom and the 15 healthy volunteers of the cMAC database. The TDFFD was modified in two ways. First, we modified the similarity metric to incorporate frame to frame intensity differences. Second, on volunteer sequences, we performed the tracking backward in time since the first frames did not show the contrast between blood and myocardium, making these frames poor choices of reference. On the phantom, we propagated a grid adjusted to tag lines to all frames for visually assessing the influence of the different algorithmic parameters. The weight between the two metric terms appeared to be a critical parameter for making a compromise between good tag tracking while preventing drifts and avoiding tag jumps. For each volunteer, a volumet-ric mesh was defined in the Steady-State Free Precession (SSFP) image, at the closest cardiac time from the last frame of the tagging sequence. Uniform strain patterns were observed over all myocardial segments, as physiologically expected
Temporal diffeomorphic Free Form Deformation to quantify changes induced by left and right bundle branch block and pacing
International audienceThis paper presents motion and deformation quantification results obtained from synthetic and in vitro phantom data provided by the second cardiac Motion Analysis Challenge at STACOM-MICCAI. We applied the Temporal Diffeomorphic Free Form Deformation (TDFFD) algorithm to the datasets. This algorithm builds upon a diffeomorphic version of the FFD, to provide a 3D + t continuous and differentiable transform. The similarity metric includes a comparison between consecutive images, and between a reference and each of the following images. Motion and strain accuracy were evaluated on synthetic 3D ultrasound sequences with known ground truth motion. Experiments were also conducted on in vitro acquisitions
Atlas construction and image analysis using statistical cardiac models
International audienceThis paper presents a brief overview of current trends in the construction of population and multi-modal heart atlases in our group and their application to atlas-based cardiac image analysis. The technical challenges around the construction of these atlases are organized around two main axes: groupwise image registration of anatomical, motion and fiber images and construction of statistical shape models. Application-wise, this paper focuses on the extraction of atlas-based biomarkers for the detection of local shape or motion abnormalities, addressing several cardiac applications where the extracted information is used to study and grade different pathologies. The paper is concluded with a discussion about the role of statistical atlases in the integration of multiple information sources and the potential this can bring to in-silico simulations
Learning correspondences of cardiac motion from images using biomechanics-informed modeling
Learning spatial-temporal correspondences in cardiac motion from images is
important for understanding the underlying dynamics of cardiac anatomical
structures. Many methods explicitly impose smoothness constraints such as the
norm on the displacement vector field (DVF), while usually
ignoring biomechanical feasibility in the transformation. Other geometric
constraints either regularize specific regions of interest such as imposing
incompressibility on the myocardium or introduce additional steps such as
training a separate network-based regularizer on physically simulated datasets.
In this work, we propose an explicit biomechanics-informed prior as
regularization on the predicted DVF in modeling a more generic biomechanically
plausible transformation within all cardiac structures without introducing
additional training complexity. We validate our methods on two publicly
available datasets in the context of 2D MRI data and perform extensive
experiments to illustrate the effectiveness and robustness of our proposed
methods compared to other competing regularization schemes. Our proposed
methods better preserve biomechanical properties by visual assessment and show
advantages in segmentation performance using quantitative evaluation metrics.
The code is publicly available at
\url{https://github.com/Voldemort108X/bioinformed_reg}.Comment: Accepted by MICCAI-STACOM 2022 as an oral presentatio
WarpPINN: Cine-MR image registration with physics-informed neural networks
Heart failure is typically diagnosed with a global function assessment, such
as ejection fraction. However, these metrics have low discriminate power,
failing to distinguish different types of this disease. Quantifying local
deformations in the form of cardiac strain can provide helpful information, but
it remains a challenge. In this work, we introduce WarpPINN, a physics-informed
neural network to perform image registration to obtain local metrics of the
heart deformation. We apply this method to cine magnetic resonance images to
estimate the motion during the cardiac cycle. We inform our neural network of
near-incompressibility of cardiac tissue by penalizing the jacobian of the
deformation field. The loss function has two components: an intensity-based
similarity term between the reference and the warped template images, and a
regularizer that represents the hyperelastic behavior of the tissue. The
architecture of the neural network allows us to easily compute the strain via
automatic differentiation to assess cardiac activity. We use Fourier feature
mappings to overcome the spectral bias of neural networks, allowing us to
capture discontinuities in the strain field. We test our algorithm on a
synthetic example and on a cine-MRI benchmark of 15 healthy volunteers. We
outperform current methodologies both landmark tracking and strain estimation.
We expect that WarpPINN will enable more precise diagnostics of heart failure
based on local deformation information. Source code is available at
https://github.com/fsahli/WarpPINN.Comment: 18 pages, 10 figure
Atlas-Based Quantification of Myocardial Motion Abnormalities: Added-Value for Understanding the Effect of Cardiac Resynchronization Therapy
International audienc
Atlas-based Quantification of Myocardial Motion Abnormalities: Added-value for the Understanding of CRT Outcome?
International audienceIn this paper, we present the use of atlas-based indexes of abnormality for the quantification of cardiac resynchronization therapy (CRT) outcome in terms of motion. We build an atlas of normal motion from 21 healthy volunteers to which we compare 88 CRT candidates before and after the therapy. Abnormal motion is quantified locally in time and space using a statistical distance to normality, and changes induced by the therapy are related with clinical measurements of CRT outcome. Results correlate with recent clinical hypothesis about CRT response, namely that the correction of specific mechanisms responsible for cardiac dyssynchrony conditions the response to the therapy
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