# A Workflow for Creating Gastric Computational Models from SPARC Scaffolds
## 3 Results
### Slow Wave Simulation Results  
A normal antegrade (i.e., proximal to distal) slow wave propagation was simulated using the three FEM models, with the activity starting at the same pacemaker region just below the fundus (indicated with the green star in Figure 5). Slow wave activity was simulated for 200 s for all three FEM models, which took 38 h to solve for the varying thickness 3D model (see Table 1). The simulation with the fixed thickness 3D model was much faster and took 26 h to complete. However, the 2D surface model provided the computationally fastest simulation amongst the three models, taking approximately 8 min to solve a 200 s simulation. Slow wave simulations converged after around 80 s of simulation time for all three FEM models. The difference (i.e., error) between the mean activation period of pacemaker nodes and non-pacemaker nodes decreased from 20% to less than 1% within the first 80 s.  
Periodic slow wave cycles were activated in approximately 14 s, and each cycle took around 20 s to terminate at the distal stomach. Therefore, a maximum of two waves were present in the stomach at any time, consistent with experimental observations [32; 37]. Figure 5 shows the signal traces for nine solution points as marked on the stomach geometry. In all cases, the activity first propagated in the circumferential direction (indicated by the earlier activation of G than B) and formed a ring that propagated in the proximal to distal direction. The cellular activation in the two 3D volume models was nearly identical; however, the 2D surface model showed either delayed or early activation in certain regions within the stomach compared to the 3D models. The largest delay was observed in the distal corpus on the greater curvature (Figure 5B), while the delay was reduced more distally (Figure 5C) to the level of delay observed more proximally (Figure 5A). On the  
Figure 4: Three computational stomach meshes generated from the rat stomach scaffold: **(a)** a 2D triangular surface mesh with a 0 μm thickness corresponding to the serosal surface of the stomach, **(b)** a 3D tetrahedral volume mesh corresponding to the longitudinal and circular muscle layers in the scaffold with a fixed 115 μm thickness, and **(c)** a 3D tetrahedral volume mesh incorporating the regional thickness properties of the rat stomach available in the literature. The color scale represents the full wall thickness and green rectangles show an enlarged view of the meshes. Computed fibers within the longitudinal and circular muscle layers are shown in **(d,e)**, respectively. The approximate location of the lower esophageal sphincter (LES) is identified with an arrow.  
other hand, the 2D surface model had slightly earlier activation on the proximal lesser curvature, but the activation was delayed as it propagated distally (Figure 5G-I).  
The AT maps of the three FEM models for one slow wave cycle are shown in Figure 6, displaying the time taken for each cell to be activated after the slow wave initiated at the pacemaker region. The cells in the pink region, corresponding to the fundus region, were not activated since they were assigned to passive cells. The fundus was approximated using a threshold value for the Laplace solution along the longitudinal axis of the stomach, resulting in a sharp boundary line between activated and non-activated cells, which is likely not observed in the stomach in-vivo. The overall activation and propagation profiles of the three models were in good agreement, but the 2D surface model showed some differences in the earlier phase of the slow wave cycle. The mean AT difference between the 2D surface model and the varying thickness 3D model was 0.2 \(\pm\) 0.3 s while the highest difference of 1 s was observed in the most distal region of the stomach. The mean AT difference between the fixed and varying thickness 3D models was only 0.1 \(\pm\) 0.2 s with the highest difference of 0.5 s in the most distal region of the stomach.