# A Workflow for Creating Gastric Computational Models from SPARC Scaffolds
## 4 Discussion
The 2D surface model included the least complex anatomical features among the three FEM models but provided the fastest slow wave simulations. The whole-organ slow wave simulation for 200 s was completed in only 8 min. This represents a significant advancement for performing rapid simulations to assess the efficacy of a vast range of stimulation parameters [23]. In addition, this model could be used for investigating the long-term outcomes of electrical therapies through simulations over many hours, needed to investigate the digestion process realistically. The fixed thickness 3D FEM model incorporated the muscle fiber orientation details in the LM and CM layers as reported in [14], making it ideal for coupled electromechanical simulations. However, the thin muscle layers in this model required a much more refined mesh compared to the 2D FEM model, resulting in a significantly higher computational cost. Slow wave simulation with the same duration was approximately 200 times longer than the 2D model. This could be especially problematic for simulations investigating the long-term impacts of interventions. However, with experimentally informed fiber properties, modeling mechanical behavior of the stomach can be achieved with greater accuracy using this model. The most realistic 3D FEM model with varying thickness of the LM and CM layers incorporated experimental thickness measurements across the rat stomach [14]. Although the experimental dataset was limited to 15 tissue samples from the stomach, the thickness measurements were well-distributed across the stomach surface, providing a reliable representation of regional thickness variation. Additionally, the thickness variation across the stomach was smooth with a continuously increasing trend from the greater curvature to the lesser curvature. As a result, fitting these 15 thickness values to the generic stomach model resulted in very low root-mean squared errors and hence the thickness across the stomach model was in good agreement with the reported values. Although this model is the most computationally expensive among the three FEM models (about 300 times longer than the 2D model), it enables more accurate modeling of mechanical contractions in the stomach, useful for testing and establishing experimental protocols via in-silico studies before validating in animal models. All three FEM models incorporated experimentally informed fiber orientations. Fiber orientations were computed using a Laplace solution-based method where Dirichlet boundary conditions were arbitrarily chosen. While the selection of these boundary condition values would not impact the computed fiber orientations since the gradient between two defined boundaries was used in the computation, the definition (i.e., location) of the boundaries would impact the direction of gradient vector and hence the resulting fiber orientations. Therefore, both the circumferential and longitudinal boundaries, including the arc-shaped boundary condition in the proximal stomach for the longitudinal fibers, were determined to result in fiber orientations as reported in [14]. This study also presents a robust simulation framework to model slow wave activation and propagation, and the developed FEM models were successfully used in whole-organ slow wave simulations. Simulations have shown that the fixed and varying thickness 3D models resulted in almost identical propagation maps across the stomach, as they both incorporated the fiber orientations of both the LM and CM layers. Although only the fiber orientations of CM layer were incorporated in the 2D FEM model, the overall propagation patterns and activation times across the entire stomach were similar to those obtained in the 3D FEM models. The maximum difference in the activation times between the 2D FEM model and the varying thickness 3D FEM model was only 1 s and observed in the most-distal region of the stomach.