PubMed · 13937235
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L H NAHUM. 1963. Quantitative morphology.. https://pubmed.ncbi.nlm.nih.gov/13937235/
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Segmentation of time series of 3D cardiac images is clinically used for the assessment of the mechanical function of the left ventricle. To take into account the 4D (3D+T) nature of those images, we propose to extend the deformable surface framework by introducing time-dependent constraints. Thus, in addition to computing an internal force for enforcing the regularity of the deformable model, prior motion knowledge is introduced in the deformation process through either temporal smoothing or trajectory constraints. In this paper, deformable surfaces are represented as simplex meshes owing to their generality and their ability to compute mean curvature at each vertex. The segmentation accuracy of this 4D deformable model is estimated on synthetic SPECT image sequences for which a ground truth about the LV volume is known. Segmentation of non-synthetic SPECT and other modalities 4D images is also discussed.
Pinning of vortices by defects plays an important role in various physical (superconductivity, superfluidity, etc.) or biological (propagation in cardiac muscle) situations. Which defects act as pinning centers? We propose a way to study this general problem by using an advection field to quantify the attraction between an obstacle and a vortex. A full solution is obtained for the real Ginzburg-Landau equation (RGLE). Two pinning mechanisms are found in excitable media. Our results suggest strong analogies with the RGLE when the heterogeneity is excitable. Unpinning from an unexcitable obstacle is qualitatively harder, resulting in a stronger pinning force. We discuss the implications of our results to control vortices and propose experiments in a chemical active medium and in cardiac tissue.
If the heart fails to recover sufficient functionality following an infarct, then heart failure develops, an important cause of death in the western world. One obvious therapy is to create more muscle tissue to supplement the damaged myocardium with new functional contractile cells, together with neovasculogenesis. Stem cells repair recipient tissue by differentiating into tissue-specific cells or by creating an environment that stimulates the process of repair by the body's own cells at the site. In animal studies the heart function stabilised following an injection of stem cells in the infarcted area. In 3 non-randomised trials in humans, bone marrow stem cells were injected via the infarcted artery or round the infarcted area; the results indicated an improved heart function. There is currently still insufficient fundamental knowledge about the behaviour of multipotent cells, about the effects of using them for treatment, and about their long-term risk for these cells to be employed in the treatment of patients with a heart infarct.