We present the development and testing of a semi-automated tool to support the diagnosis of left ventricle (LV) dysfunctions from cardiac magnetic resonance (CMR). CMR short-axis images of the LVs were obtained in 15 patients and processed to detect endocardial and epicardial contours and compute volume, mass and regional wall motion (WM). Results were compared with those obtained from manual tracing by an expert cardiologist. Nearest neighbour tracking and finite-element theory were merged to calculate local myocardial strains and torsion. The method was tested on a virtual phantom, on a healthy LV and on two ischaemic LVs with different severity of the pathology. Automated analysis of CMR data was feasible in 13/15 patients: computed LV volumes and wall mass correlated well with manually extracted data. The detection of regional WM abnormalities showed good sensitivity (77.8%), specificity (85.1%) and accuracy (82%). On the virtual phantom, computed local strains differed by less than 14 per cent from the results of commercial finite-element solver. Strain calculation on the healthy LV showed uniform and synchronized circumferential strains, with peak shortening of about 20 per cent at end systole, progressively higher systolic wall thickening going from base to apex, and a 108 torsion. In the two pathological LVs, synchronicity and homogeneity were partially lost, anomalies being more evident for the more severely injured LV. Moreover, LV torsion was dramatically reduced. Preliminary testing confirmed the validity of our approach, which allowed for the fast analysis of LV function, even though future improvements are possible.

We aim at testing the possibility to build patientspecific structural finite element models (FEMs) of the mitral valve (MV) from cardiac magnetic resonance (CMR) imaging and to use them to predict the outcome of mitral annuloplasty procedures. MV FEMs were built for one healthy subject and for one patient with ischemic mitral regurgitation. On both subjects, CMR imaging of 18 longaxis planes was performed with a temporal resolution of 55 time-frames per cardiac cycle. Three-dimensional MV annulus geometry, leaflets surface and PM position were manually obtained using custom software. Hyperelastic anisotropic mechanical properties were assigned to MV tissues. A physiological pressure load was applied to the leaflets to simulate valve closure until peak systole. For the pathological model only, a further simulation was run, simulating undersized rigid annuloplasty before valve closure. Closure dynamics, leaflets stresses and tensions in the subvalvular apparatus in the healthy MV were consistent with previous computational and experimental data. The regurgitant valve model captured with good approximation the real size and position of regurgitant areas at peak systole, and highlighted abnormal tensions in the annular region and sub-valvular apparatus. The simulation of undersized rigid annuloplasty showed the restoration of MV continence and normal tensions in the subvalvular apparatus and at the annulus. Our method seems suitable for implementing detailed patient-specific MV FEMs to simulate different scenarios of clinical interest. Further work is mandatory to test the method more deeply, to reduce its computational time and to expand the range of modeled surgical procedures.

Magnetic resonance imaging (MRI) represents the gold standard for left ventricular (LV) volumes and mass analysis, as well as for the diagnosis of regional LV dysfunction. However, volumetric measurements based on multiple contour tracings are cumbersome, and visual interpretation of cine images suffers from inter-observer variability. Our aim was to develop a technique for combined automated endo and epicardial border detection from MRI images throughout the cardiac cycle, and to validate it. Methods Dynamic, ECG-gated, steady-state free precession short-axis images were obtained (GE Healthcare, 1.5T) in 8–12 slices in 15 patients with previous myocardial infarction. An expert cardiologist provided the “gold standard” for: 1) LV dimensions and mass, by manually tracing endo and epicardial contours; 2) regional wall motion (WM) interpretation, by grading (normal, abnormal) three slices selected at apical, mid and basal level. Custom software based on image noise distribution (for LV endocardial detection) and level-set (for epicardial detection) was applied, from which end-diastolic (ED) and end-systolic (ES) volumes and mass were computed, as well as regional fractional area change (RFAC), from which automated classification of regional WM abnormality was defined for RFAC<50%. Comparison with “gold standard” was performed by: 1) linear regression and Bland-Altman analyses for LV volumes and mass; 2) levels of agreement between the cardiologist WM grades and the automated classification. Results Optimal correlations (r2>.97) and no bias were found for ED and ES volumes, while LV mass resulted in a good correlation (ED: r2=.81; ES: r2=.74) with a minimal overestimation (ED:15.2g; ES:8.7g) and narrow 95% limits of agreement (ED: ±30 g; ES: ±33g). The automated interpretation resulted in high sensitivity, specificity, and accuracy (78%, 85%, 82%, respectively) of WM abnormalities. Conclusion Combined automated endo and epicardial border detection from MRI images provides reliable measurements of LV dimensions and regional WM classification. Full Text

Mitral annulus (MA) assessment is of great importance for the diagnosis and treatment of mitral valve (MV) disease. Standard CMR image acquisition allows to obtain only a limited number of measurements. We propose a different way to study the MV by multiple CMR long-axis cine images, followed by 3D reconstruction and quantification. Our aim was to test the reproducibility of this approach. Methods and Results CMR cine imaging of 18 long-axis planes (55 frames/cardiac cycle; spatial resolution: 0.78 mm; slice thickness: 8mm), rotated every 10°along the left ventricular long-axis, was performed in 12 patients with myocardial infarction. Custom software was used for MV quantitative nalysis: 1) in the end-diastolic (ED) and end-systolic (ES) frames, in each plane, the position of the MA annulus and papillary muscles (PM) tips were manually identified; 2) the MA geometry and PM position were automatically reconstructed in a 3D space; 3) several parameters were then computed: MA perimeter, antero-posterior and intercommissural diameters, MA height, MA 3D and projected area, the angle between PM, the distance from PM to the MA. To assess the reproducibility of the procedure, two operators repeated the analysis: the inter-operator variability was evaluated as the coefficient of variation (CV(%)=100*SD/mean). Analysis of MA was feasible in all patients, showing good inter-operator agreement for MA perimeter (CVED=1.9%; CVES=1.8%), antero-posterior (CVED=3.0%; CVES=5.8%) and intercommissural diameters (CVED=1.8%; CVES=2.0%), 3D (CVED=3.4%; CVES=4.3%) and projected areas (CVED=2.8%; CVES=3.7%), and the distance from PM and MA (CVED=4.1%; CVES=4.6%). MA height (CVED=9.9%; CVES=16.1%) and the angle between PM (CVED=6.8%; CVES=10.6%) were less reproducible, in particular at ES. Conclusion Quantitative information on MA and PM morphology and function is feasible from CMR imaging n multiple long-axis planes. The proposed approach is highly reproducible and could constitute the basis for in-depth evaluation of the MV and for the planning of surgical procedures. Full Text

Biomechanical data of the mitral apparatus could serve as a basis for finite element (FE) analyses of the mitral valve (MV) in ischemic patients. Previously FE models were mostly based on simplifying assump-tions on MV symmetrical shape, idealized leaflets free-edge profile and neg-lected papillary muscles (PMs) contraction. To overcome these limitations, we aimed at developing a framework for the quantitative analysis of time-varying MV geometry from cardiac magnetic resonance (CMR) imag-ing, and to integrate these data in a patient-specific structural simulation of MV closure. Methods CMR imaging of 18 long-axis planes (one every 10 degrees) was performed on three ischemic patients with a temporal resolution of 55 time-frames per cardiac cycle. Three-dimensional MV annulus geometry, leaflets surface and PMs position were manually obtained using custom software. Leaflets extent and 3D orientation were set consistently with the MRI-derived leaflets free-edge profile. Hyperelastic aniso-tropic mechanical properties were assigned to the MV tissues, and a physiological pressure load curve was applied to the leaflets. Results In the studied subjects, preliminary results concerning dif-ferent aspects of MV biomechanics, such as valve dynamics, leaflets coaptation, leaflets strains and chordae tendineae tensions, were in good agreement with in vitro observations. Conclusion In this study, we introduced a novel approach for developing a FE model of the MV based on patient-specific data obtained from CMR. This technique allows for high time-resolution imaging in adequately large field of view, even in subjects with enlarged annulus due to MV pathologies. This approach could constitute the basis for accurate evaluation of MV pa-thologic conditions and for the planning of surgical procedures. Full Text