A congenital heart defect (CHD) is an anomaly in the structure of the heart that is present at birth. In the last 15 years, a CHD is present in 9 per 1,000 live births, making it the most prevalent birth defect (Linde et al., 2011).
CHD’s prevalence coupled with its inherent complexity culminates into situations that are both complicated and unique. This makes the treatment of patients with CHDs highly patient-specific. Patient-specific physics-based computational models can aid in selecting the optimal course of treatment for the patient and serve as a predictive tool for different surgical plans (Capelli et al., 2011). The creation of patient-specific geometric heart models of children with CHDs will be the first crucial step towards a patient-specific approach in ameliorating this challenge. Approaches have to be found to face challenges including: a lack of high quality imaging data of the target population; slice misalignment due to breathing in a breath-hold procedure; and a lack of protocols in image segmentation.

To accomplish the objective, seven biventricular geometric models and meshes are created for healthy hearts, tetralogy of Fallot hearts and Fontan hearts. Slice misalignment is corrected using contours of the papillary muscle and the epicardium as a reference. Lastly, ground truth geometries are constructed by stacking disks that originate directly from the MRI segmentation.
To validate the geometric models, global and local approaches are used. The global validation includes ventricular mass and volume analyses with a relative error (RE) ranging from 0.00036 to 0.79. The Dice similarity coefficient (DSC) for the local validation is between 0.711 +/- 0.138 and 0.968 +/- 0.018. The slice misalignment correction is validated using qualitative and quantitative measures. A quantitative measure is the 4-chamber long-axis local validation which has a DSC of 0.877 for the epicardium and 0.916 for the papillary muscle correction method. Global validation in the ground truth exercise has a mean RE of 0.010 +/- 0.0066. Results of the local validation show a minimum DSC of 0.960 +/- 0.008.

Large differences in RE can be explained by the small number of MRI slices available, segmentation variability, the complex geometry of the right ventricle, and the methods of volume and mass computations. The DSC computed in the local validation of the models shows good to excellent agreement for all models. According to the long-axis local validation, the papillary muscle is the best reference method proposed for the slice misalignment correction. The ground truth exercise reveals close correlation to the Medis Suite measurements, possibly leading to underestimation of the computed volumes.

Patient-specific biventricular geometric models are created and validated in this thesis. The models are representative of a range of patients including healthy hearts and hearts with complex CHDs. A patient-specific model of the heart would be beneficial for clinicians to understand complex pathological cases, as the ones described in this work. Herein, a patient-specific biventricular geometric model is presented. By including a healthy population as well as patients affected by complex congenital heart defects, this work can be used as a starting point for the development of more patient-specific computational models of the heart.