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- Bernard, Olivier, et al.
(författare)
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Standardized evaluation system for left ventricular segmentation algorithms in 3D echocardiography.
- 2016
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Ingår i: IEEE Transactions on Medical Imaging. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0062 .- 1558-254X. ; 35:4, s. 967-977
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Tidskriftsartikel (refereegranskat)abstract
- Real-time 3D Echocardiography (RT3DE) has been proven to be an accurate tool for left ventricular (LV) volume assessment. However, identification of the LV endocardium remains a challenging task, mainly because of the low tissue/blood contrast of the images combined with typical artifacts. Several semi and fully automatic algorithms have been proposed for segmenting the endocardium in RT3DE data in order to extract relevant clinical indices, but a systematic and fair comparison between such methods has so far been impossible due to the lack of a publicly available common database. Here, we introduce a standardized evaluation framework to reliably evaluate and compare the performance of the algorithms developed to segment the LV border in RT3DE. A database consisting of 45 multivendor cardiac ultrasound recordings acquired at different centers with corresponding reference measurements from 3 experts are made available. The algorithms from nine research groups were quantitatively evaluated and compared using the proposed online platform. The results showed that the best methods produce promising results with respect to the experts' measurements for the extraction of clinical indices, and that they offer good segmentation precision in terms of mean distance error in the context of the experts' variability range. The platform remains open for new submissions.
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- Galderisi, Maurizio, et al.
(författare)
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Recommendations of the European Association of Echocardiography : how to use echo-Doppler in clinical trials
- 2011
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Ingår i: European Journal of Echocardiography. - : Oxford University Press (OUP). - 1525-2167 .- 1532-2114. ; 12:5, s. 339-353
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Tidskriftsartikel (refereegranskat)abstract
- The European Association of Echocardiography (EAE) has developed the present recommendations to assist clinical researchers in the design, implementation, and conduction of echocardiographic protocols for clinical trials and to guarantee their quality. Clinical trials should be designed and conducted based on the knowledge of the pathophysiology of the clinical condition studied, the technical characteristics of the echo-Doppler modalities, and the variability of the tested parameters. These procedures are important to choose the most reliable and reproducible techniques and parameters. Quality assurance must be guaranteed by adequate training of peripheral site operators to obtain optimal echo-Doppler data and by using a core laboratory for accurate and reproducible data analysis.
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- Larsson, Matilda, et al.
(författare)
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A novel measure to express tracking quality in ultrasound block matching
- 2010
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Ingår i: Proceedings - IEEE Ultrasonics Symposium. - 9781457703829 ; , s. 1636-1639
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Konferensbidrag (refereegranskat)abstract
- Speckle de-correlation is a major problem in block matching based ultrasound methodologies as it limits the accuracy of the tracking result. It would be of benefit to have a quantitative measure expressing the local tracking quality as it would allow discarding unreliable motion estimates. We hypothesized that kernels showing sufficient gray scale pattern would more reliably track than kernels with more homogenous gray scale distributions. The aim of this study was to test this hypothesis in-silico. Ultrasound B-mode sequences were simulated from a kinematic model of the carotid artery. Two-dimensional motion was estimated using block matching with the normalized cross-correlation function as similarity measure. For each kernel, two measures of tracking quality were stored: the normalized cross-correlation coefficient (Ccc) and a measure of the amount of edges inside the kernel detected using a canny filter and counted on a pixel-by-pixel basis. As such, a quality measure (Cedge) between 0 (no edges) and 1 (nothing but edges) was obtained. Axial and lateral strains were subsequently obtained by linear regression in regions of interest (ROIs) with best/worst mean tracking quality scores. The root-mean-squared-error (RMSE) was significantly lower in regions with low Ccc (worst ROI) compared to ROIs with high Ccc. However, more edges in the kernel did indeed result in better overall tracking (lower RMSE). Thus, the proposed edge-detection method showed to be a better tracking quality measure than the commonly used Ccc.
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- Larsson, Matilda, 1981-, et al.
(författare)
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Ultrasound-based 2D Strain Estimation of the Carotid Artery : an in-silico feasibility study
- 2009
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Ingår i: Ultrasonics Symposium (IUS), 2009 IEEE International. - : IEEE. - 9781424443895 ; , s. 5441992-
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Konferensbidrag (refereegranskat)abstract
- Ultrasound based estimation of arterial wall properties is commonly used to assess vessel wall stiffness in studies of vascular diseases. Recently, it was shown that the longitudinal motion of the vessel during systole can be measured using speckle tracking. However, the assessment of longitudinal strain in the vessel wall has to be further investigated. The aim of this study was to test the feasibility of simultaneous assessment of radial and longitudinal strain in the carotid artery using computer simulations. A kinematic cylindrical model of the carotid artery with realistic dimensions was constructed. The model was deformed radially according to temporal distention measured in-vivo while longitudinal deformation was the result of conservation of volume. Moreover, longitudinal motion was superimposed based on profiles obtained in-vivo. Ultrasound long axis images were simulated using a generalized convolution model (COLE) with realistic image properties. Four models with different scatterer distributions were built. For each of them, longitudinal and radial motion were estimated using normalized cross-correlation with spline interpolation to detect sub-sample motion. Radial and longitudinal strains, obtained by linear regression were compared with the ground truth from the model. The maximal systolic radial strain was estimated to be -12.77 ± 0.4% (ground truth -13.89%) while longitudinal strain was 5.21 ± 0.67% (ground truth 5.3%). This study shows the feasibility of simultaneously measuring radial and longitudinal strain in the carotid artery by making use of currently available hardware.
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- Smoljkić, M., et al.
(författare)
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Comparison of in vivo vs. ex situ obtained material properties of sheep common carotid artery
- 2018
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Ingår i: Medical Engineering and Physics. - : Elsevier. - 1350-4533 .- 1873-4030. ; 55, s. 16-24
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Tidskriftsartikel (refereegranskat)abstract
- Patient-specific biomechanical modelling can improve preoperative surgical planning. This requires patient-specific geometry as well as patient-specific material properties as input. The latter are, however, still quite challenging to estimate in vivo. This study focuses on the estimation of the mechanical properties of the arterial wall. Firstly, in vivo pressure, diameter and thickness of the arterial wall were acquired for sheep common carotid arteries. Next, the animals were sacrificed and the tissue was stored for mechanical testing. Planar biaxial tests were performed to obtain experimental stress-stretch curves. Finally, parameters for the hyperelastic Mooney–Rivlin and Gasser–Ogden–Holzapfel (GOH) material model were estimated based on the in vivo obtained pressure-diameter data as well as on the ex situ experimental stress-stretch curves. Both material models were able to capture the in vivo behaviour of the tissue. However, in the ex situ case only the GOH model provided satisfactory results. When comparing different fitting approaches, in vivo vs. ex situ, each of them showed its own advantages and disadvantages. The in vivo approach estimates the properties of the tissue in its physiological state while the ex situ approach allows to apply different loadings to properly capture the anisotropy of the tissue. Both of them could be further enhanced by improving the estimation of the stress-free state, i.e. by adding residual circumferential stresses in vivo and by accounting for the flattening effect of the tested samples ex vivo.
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