Atrial fibrillation (AF) is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation with consequent deterioration of mechanical function.Personalized computational modeling provides a novel framework for integrating and interpreting the combined role of atrial electrophysiology and mechanics in AF development and sustenance.Coronary computed tomography angiography data were segmented using a threshold-based approach and the smoothed voxel representation was discretized into a high-resolution tetrahedral finite element (FE) mesh.To estimate the complex left atrial fiber architecture, individual fiber fields were generated according to morphological data on the endo-and epicardial surfaces based on local solutions of Laplace's equation and transmurally interpolated to all tetrahedral elements.Personalized geometrical models included the heterogeneous thickness distribution of the left atrial myocardium and subsequent discretization led to high-fidelity tetrahedral FE meshes.The novel algorithm for (automated) incorporation of the left atrial fiber architecture provided a realistic estimate of the atrial microstructure and was able to qualitatively capture all important fiber bundles.The established modeling pipeline provides a robust framework for the rapid development of personalized model cohorts and facilitates simulations of atrial electromechanics.
Hypertrophic cardiomyopathy (HCM) is a disease with marked genetic and phenotypic heterogeneity. It is well known that obstructive septal forms of this disease entail worse clinical outcome compared with nonobstructive septal and apical forms. The objective of this study was to analyze the differences in left ventricular diastolic function in different subgroups of HCMs and to assess the influence of the location of myocardial hypertrophy and the presence of dynamic obstruction on impairment of diastolic function and its correlation with the clinical status.We studied 86 patients with HCM; 27 with the obstructive asymmetric septal type (OAS), 37 with the nonobstructive asymmetric septal type (NOAS) and 22 with apical hypertrophic cardiomyopathy (ApHCM). Patients underwent conventional and tissue Doppler echocardiography and were assessed applying the latest recommendations regarding diastolic dysfunction. Cardiac magnetic resonance was used to study the various morphologic subtypes and quantify left ventricular mass (LVM).The early diastolic annular velocity (e') was significantly lower in OAS with a median of 5 cm/s compared with NOAS with 7 cm/s and ApHCM with 7.5 cm/s (P = 0.0002), and the E/e' ratio was 8.5 in ApHCM, 10 in NOAS and 14 in OAS (P = 0.0001); no significant differences were found in LVM or maximal wall thickness.In HCM, the location of left ventricular hypertrophy and the presence of dynamic obstruction affect the degree of diastolic dysfunction; impairment is greater in patients with the OAS type, and markedly less in patients with apical involvement.
Active shape models bear a great promise for model-based medical image analysis. Their practical use, though, is undermined due to the need to train such models on large image databases. Automatic building of point distribution models (PDMs) has been successfully addressed and a number of autolandmarking techniques are currently available. However, the need for strategies to automatically build intensity models around each landmark has been largely overlooked in the literature. This work demonstrates the potential of creating intensity models automatically by simulating image generation. We show that it is possible to reuse a 3D PDM built from computed tomography (CT) to segment gated single photon emission computed tomography (gSPECT) studies. Training is performed on a realistic virtual population where image acquisition and formation have been modeled using the SIMIND Monte Carlo simulator and ASPIRE image reconstruction software, respectively. The dataset comprised 208 digital phantoms (4D-NCAT) and 20 clinical studies. The evaluation is accomplished by comparing point-to-surface and volume errors against a proper gold standard. Results show that gSPECT studies can be successfully segmented by models trained under this scheme with subvoxel accuracy. The accuracy in estimated LV function parameters, such as end diastolic volume, end systolic volume, and ejection fraction, ranged from 90.0% to 94.5% for the virtual population and from 87.0% to 89.5% for the clinical population.
This fileset is associated with the Left Atrial Segmentation Challenge 2013 (LASC'13). LASC'13 was part of the STACOM'13 workshop, held in conjunction with MICCAI'13. Seven international research groups, comprising 11 algorithms, participated in the challenge. For a detailed report, please refer to: Tobon-Gomez C, Geers AJ, Peters, J, Weese J, Pinto K, Karim R, Ammar M, Daoudi A, Margeta J, Sandoval Z, Stender B, Zheng Y, Zuluaga, MA, Betancur J, Ayache N, Chikh MA, Dillenseger J-L, Kelm BM, Mahmoudi S, Ourselin S, Schlaefer A, Schaeffter T, Razavi R, Rhode KS. Benchmark for Algorithms Segmenting the Left Atrium From 3D CT and MRI Datasets. IEEE Transactions on Medical Imaging, 34(7):1460–1473, 2015. The challenge is also featured on http://www.cardiacatlas.org/challenges/left-atrium-segmentation-challenge/The data and code of the challenge have been made publicly available to serve as a benchmark for left atrial segmentation algorithms. Code is hosted on https://github.com/catactg/lasc Feel free to contact us with any questions. This fileset consists of results from algorithms evaluated during LASC'13. Included are the binary mask provided by the participant and the output files of lasc/code/lasc_benchmark.py in the code repository. dm_body.csv: Dice metric of the LA body dm_pvs.csv: Dice metric of the PVs mask.mhd + mask.raw: Binary mask provided by segmentation algorithm mesh.vtp: Surface mesh extracted from mask.mhd using marching cubes s2s_body.csv: Surface-to-surface metric of the LA body s2s_pvs.csv: Surface-to-surface metric of the PVs std_gt2seg.vtp: Surface mesh with distance from GT to segmentation (as pointdata array) std_mesh.vtp: Surface mesh after standardisation std_seg2gt.vtp: Surface mesh with distance from segmentation to GT (as pointdata array) std.mhd + std.zraw: Image representation of segmentation with labels copied from std_mesh.vtp