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Aims: Reliable evaluation of the severity and consequences of pulmonary regurgitation (PR) in patients with repaired tetralogy of Fallot (TOF) is crucial to timely identify the need for pulmonary valve intervention. We aimed to identify the accuracy of echocardiographic parameters to differentiate between moderate and severe PR, using phase contrast cardiac magnetic resonance imaging (CMR) as gold standard. Methods and results: In this cross-sectional study, 45 TOF patients with both echocardiographic and CMR measurements of PR were enrolled. All quantitative and semiquantitative echocardiographic measurements such as pressure half time (PHT), Color flow jet width (CFJW), ratio CFJW/right ventricle outflow tract (RVOT) diameter, PR index and the presence of early termination of the PR jet, end-diastolic antegrade flow and diastolic backflow in main pulmonary artery (MPA), and PA branches correlated significantly with PR fraction on CMR. Qualitative assessment with color flow on echocardiography overestimated PR Multivariate linear regression analysis identified the ratio of CFJW/RVOT diameter and PHT as independent predictors of PR fraction. Accuracy of echo parameters was tested to differentiate between mild-to-moderate and severe PR Combining different echocardiographic parameters increased sensitivity and specificity. The addition of diastolic flow reversal in the PA branches to PHT below 167 milliseconds increased the NPV from 87% to 89% and PPV from 62% to 76%. Conclusions: Comparison with CMR confirms that echocardiographic parameters are reliable in predicting PR severity. Combined measurement of diastolic flow reversal in the pulmonary artery branches and PHT is reliable in the detection of severe PR in the follow-up of TOF patients.

The most widespread technique used to register sets of medical images consists of selecting one image as fixed reference, to which all remaining images are successively registered. This pairwise scheme requires one optimization procedure per pair of images to register. Pairwise mutual information is a common dissimilarity measure applied to a large variety of datasets. Alternative methods, called groupwise registrations, have been presented to register two or more images in a single optimization procedure, without the need of a reference image. Given the success of mutual information in pairwise registration, we adapt one of its multivariate versions, called total correlation, in a groupwise context. We justify the choice of total correlation among other multivariate versions of mutual information, and provide full implementation details. The resulting total correlation measure is remarkably close to measures previously proposed by Huizinga et al. based on principal component analysis. Our experiments, performed on five quantitative imaging datasets and on a dynamic CT imaging dataset, show that total correlation yields registration results that are comparable to Huizinga’s methods. Total correlation has the advantage of being theoretically justified, while the measures of Huizinga et al. were designed empirically. Additionally, total correlation offers an alternative to pairwise mutual information on quantitative imaging datasets.

It is estimated that each year, 30,000 people in the Netherlands suffer from myocardial infarction, and is in fact a major public health care burden. Next to ischaemic heart disease (IHD), thanks to modern medicine, more and more patients with congenital heart disease (CHD) reach adulthood, but nonetheless require lifelong professional care. Imaging techniques are essential in these two groups of patients for establishing diagnosis, guiding therapy and predicting outcomes. This thesis investigated the application of cardiac MRI in patients with IHD and CHD and evaluated novel non-invasive MRI techniques in both humans and in a porcine model. In this thesis we showed that cardiac MRI is an excellent tool for the evaluation of atherosclerotic and congenital cardiovascular disease. It is an excellent tool in predicting outcome after STEM! in patients undergoing primary percutaneous coronary intervention. Furthermore, studied in this thesis, the incidence of per procedural complications in patients with CHD seems higher than in the general population suggesting that placement of a pacemaker device might be challenging in this group of patients.

Rationale and Objectives: Magnetic resonance angiography (MRA) is a well-established modality for the assessment of renal artery stenosis. Using dedicated quantitative analyses, MRA can become a useful tool for assessing renal artery dimensions in patients referred for renal sympathetic denervation (RDN) and for providing accurate measurements of vascular response after RDN. The purpose of this study was to test the reproducibility of a novel MRA quantitative imaging tool and to validate these measurements against intravascular ultrasound (IVUS). Materials and Methods: In nine patients referred for renal denervation, renal artery dimensions were measured. Bland-Altman analysis was used to assess the intraobserver and interobserver reproducibility. Results: Mean lumen diameter was 5.8 ± 0.7 mm, with a very good intraobserver and interobserver variability of 0.7% (reproducibility: bias, 0 mm; standard deviation [SD], 0.1 mm) and 1.2% (bias, 0 mm; SD, 0.1 mm), respectively. Mean total lumen volume was 1035.3 ± 403.6 mm3 with good intraobserver and interobserver variability of 2.9% (bias, -9.7 mm3; SD, 34.0 mm3) and 2.8% (bias, -11.4 mm3; SD, 42.4 mm3). The correlation (Pearson R) between mean lumen diameter measured with MRA and IVUS was 0.750 (P = .002). Conclusions: Using a novel MRA quantitative imaging tool, renal artery dimensions can be measured with good reproducibility and accuracy. MRA-derived diameters and volumes correlated well with IVUS measurements.