Delayed enhancement imaging in a contemporary patient cohort following correction of tetralogy of Fallot.

OBJECTIVE: To test the hypothesis that myocardial scars after repair of tetralogy of Fallot are related to impaired cardiac function and adverse clinical outcome. METHODS: A total of 53 patients were retrospectively analysed after repair of tetralogy of Fallot. The median patient age was 20 years (range 2-48). Cardiac MRI with a 1.5 T magnet included cine sequences to obtain volumes and function, phase-sensitive inversion recovery delayed enhancement imaging to detect myocardial scars, and flow measurements to determine pulmonary regurgitation fraction. In addition, clinical parameters were obtained. RESULTS: An overall 83% of patients were in NYHA class I. All patients with the exception of 2 (96%) had pulmonary insufficiency. Mean ejection fraction and end-diastolic volume index were 46% and 128 ml/m2 for the right ventricle and 54% and 82 ml/m² for the left ventricle, respectively. Excluding enhancement of the septal insertion and prosthetic patches, delayed enhancement was seen in 11/53 cases (21%). Delayed enhancement of the right ventricle was detected in 6/53 patients (11%) and of the left ventricle in 5/53 patients (9%). The patient group with delayed enhancement was significantly older (p=0.003), had later repair (p=0.007), and higher left ventricular myocardial mass index (p=0.009) compared with the group without delayed enhancement. CONCLUSIONS: This study reveals that scarring is common in patients after surgical repair of tetralogy of Fallot and is associated with older age and late repair. However, there was no difference in right ventricular function, NYHA class, or occurrence of clinically relevant arrhythmias between patients with and those without myocardial scars.

Motion-aware stroke volume quantification in 4D PC-MRI data of the human aorta.

PURPOSE: 4D PC-MRI enables the noninvasive measurement of time-resolved, three-dimensional blood flow data that allow quantification of the hemodynamics. Stroke volumes are essential to assess the cardiac function and evolution of different cardiovascular diseases. The calculation depends on the wall position and vessel orientation, which both change during the cardiac cycle due to the heart muscle contraction and the pumped blood. However, current systems for the quantitative 4D PC-MRI data analysis neglect the dynamic character and instead employ a static 3D vessel approximation. We quantify differences between stroke volumes in the aorta obtained with and without consideration of its dynamics. METHODS: We describe a method that uses the approximating 3D segmentation to automatically initialize segmentation algorithms that require regions inside and outside the vessel for each temporal position. This enables the use of graph cuts to obtain 4D segmentations, extract vessel surfaces including centerlines for each temporal position and derive motion information. The stroke volume quantification is compared using measuring planes in static (3D) vessels, planes with fixed angulation inside dynamic vessels (this corresponds to the common 2D PC-MRI) and moving planes inside dynamic vessels. RESULTS: Seven datasets with different pathologies such as aneurysms and coarctations were evaluated in close collaboration with radiologists. Compared to the experts' manual stroke volume estimations, motion-aware quantification performs, on average, 1.57% better than calculations without motion consideration. The mean difference between stroke volumes obtained with the different methods is 7.82%. Automatically obtained 4D segmentations overlap by 85.75% with manually generated ones. CONCLUSION: Incorporating motion information in the stroke volume quantification yields slight but not statistically significant improvements. The presented method is feasible for the clinical routine, since computation times are low and essential parts run fully automatically. The 4D segmentations can be used for other algorithms as well. The simultaneous visualization and quantification may support the understanding and interpretation of cardiac blood flow.

The LiverAnatomyExplorer: a WebGL-based surgical teaching tool.

The LiverAnatomyExplorer is a real-time surgical teaching tool based on state-of-the-art Web technologies such as SVG (Scalable Vector Graphics), X3D (Extensible3D), and WebGL (Web Graphics Library). Unlike other medical e-learning systems, the LiverAnatomyExplorer combines traditional clinical 2D imagery with interactive Web-based 3D models derived from patient-specific image data. The tool is enhanced by surgical videos, a self-assessment tool, and an online authoring tool with which instructors can manage the presented case studies and create multiple-choice quizzes.

Semi-automatic vortex extraction in 4D PC-MRI cardiac blood flow data using line predicates.

Cardiovascular diseases (CVD) are the leading cause of death worldwide. Their initiation and evolution depends strongly on the blood flow characteristics. In recent years, advances in 4D PC-MRI acquisition enable reliable and time-resolved 3D flow measuring, which allows a qualitative and quantitative analysis of the patient-specific hemodynamics. Currently, medical researchers investigate the relation between characteristic flow patterns like vortices and different pathologies. The manual extraction and evaluation is tedious and requires expert knowledge. Standardized, (semi-)automatic and reliable techniques are necessary to make the analysis of 4D PC-MRI applicable for the clinical routine. In this work, we present an approach for the extraction of vortex flow in the aorta and pulmonary artery incorporating line predicates. We provide an extensive comparison of existent vortex extraction methods to determine the most suitable vortex criterion for cardiac blood flow and apply our approach to ten datasets with different pathologies like coarctations, Tetralogy of Fallot and aneurysms. For two cases we provide a detailed discussion how our results are capable to complement existent diagnosis information. To ensure real-time feedback for the domain experts we implement our method completely on the GPU.

Systemic right ventricles rarely show myocardial scars in cardiac magnetic resonance delayed-enhancement imaging.

OBJECTIVES: To test the hypothesis that myocardial scars cause systolic dysfunction in patients with transposition of the great arteries and a systemic right ventricle. METHODS: We retrospectively analyzed 20 consecutive patients (10 male, mean age 27.3 years) with a systemic right ventricle who underwent cardiac magnetic resonance imaging with 1.5 T. Cine steady-state free-precession sequences were performed to obtain volumes and function. Phase-sensitive inversion-recovery (PSIR) delayed-enhancement imaging was performed to detect myocardial scars. Tricuspid insufficiency was detected with echocardiography. Furthermore, the presence of arrhythmias and New York Heart Association (NYHA) class were assessed. RESULTS: Mean ejection fraction of systemic right ventricles was 43 ± 11 %, mean end-diastolic volume index was 111 ± 37 ml/m(2). Delayed-enhancement imaging revealed only one myocardial scar in the wall of a right ventricular aneurysm. All patients but one (95 %) presented with tricuspid insufficiency. Clinically relevant arrhythmias were present in 13/20 patients (65 %). The majority of patients (90 %) were NYHA class I or II. Arrhythmias, tricuspid insufficiency and NYHA class were not associated with right ventricular ejection fraction. CONCLUSIONS: Although right ventricular function was clearly impaired in our patient cohort, there was only one myocardial scar. Our results show that myocardial scarring assessed by PSIR delayed-enhancement imaging is not the underlying pathology of systemic right ventricular failure.

Computer-aided diagnosis in breast DCE-MRI--quantification of the heterogeneity of breast lesions.

PURPOSE: In our study we aim at the quantification of the heterogeneity for differential diagnosis of breast lesions in MRI. MATERIALS AND METHODS: We tested a software tool for quantification of heterogeneity. The software tool provides a three-dimensional analysis of the whole breast lesion. The lesions were divided in regions with similar perfusion characteristics. Voxels were merged to the same region, if the perfusion parameters (wash-in, wash-out, integral, peak enhancement and time to peak) correlated to 99%. We evaluated 68 lesions from 50 patients. 31 lesions proved to be benign (45.6%) and 37 malignant (54.4%). We included small lesions which could only be detected with MRI. RESULTS: The analysis of heterogeneity showed significant differences (p<0.005; AUC 0.7). Malignant lesions were more heterogeneous than benign ones. Significant differences were also found for morphologic parameters such as shape (p<0.001) and margin (p<0.007). The analysis of the enhancement dynamics did not prove successful in lesion discrimination. CONCLUSION: Our study indicates that the region analysis for quantification of heterogeneity may be a helpful additional method to differentiate benign lesions from malignant ones.