## 10 Demonstration of Adjusting Contours for the Reconstruction of Skull Defects in CAD Modeling  
As shown in Figure 4A, we present a schematic planning of the contour reconstruction of a demonstrated case. Firstly, it is necessary to draw the axis of symmetry (the green line). The symmetric contour for the skull defect (line O') can be addressed by mirror reflecting the curvature of the contralateral skull (line O) via the axis of symmetry. Next, connect the two marginal points of the skull defect (point M and M'). Make a perpendicular bisector through the connection line. Point P represents the intersection of the O' line and the vertical bisector. Figure 4: CAD modeling with the contour adjustment of case 3. (**A**) Schematic illustration of the definition for contour elevation (Point M-E-M’-connected arc), and depression (Point M-D-M’-connected arc). (**B**) Schematic illustration of the elevated and depressed contour of the skull defect. Points E1, E2, D1, D2 represent intersection points where contours are 4 and 10 mm outwardly elevated, and inwardly depressed respectively. The reconstructed contour from the skull defect on the CT images: symmetrically filled (**E**), contour elevation of 4 (**D**), and 10 mm (**C**), contour depression 4 (**F**), and 10 mm (**G**). (**H–L**) represented the respective 3-D CAD models. Suppose point P is adjusted to elevate by X mm along the perpendicular bisector. Let the intersection with the perpendicular bisector be point E. An elevated contour is defined as follows:  
**Definition 1. **_The arc line connecting point M, M', and E._  
Figure 4B shows the schematic illustration of elevated contour of the skull defect of the demonstrated case 3. Contours were elevated outward by 4 (intersection with Point E1) and 10 mm (as indicated in Point E2). Reconstructed contours with 4 and 10 mm elevation were achieved by establishing an arc line connecting point M, M', E1, and point M, M', E2, respectively. The reconstructed contours of the skull defect with 10 and 4 mm elevation, and a regular contour of axial CT images are shown in Figure 4C-E, respectively. The corresponding 3-D models are shown as Figure 4H-J. The reconstructed artificial flap with regular and elevated contours is labeled in gray and blue, respectively. Suppose point P is adjusted to depress by Y mm along the perpendicular bisector. Let the intersection with the perpendicular bisector be point D. The depressed contour is defined as follows:  
**Definition 2. **_The arc line connecting point M, M', and D._  
As indicated in Figure 4B, contours were depressed inward 4 (intersection with Point D1) and 10 mm (as indicated in Point D2). Reconstructed contours with a 4 and 10 mm depression were established by connecting point M, M', D1, and point M, M', D2 respectively. The reconstructed contours of the skull defect with a 4 and 10 mm depression of axial CT images are shown as Figure 4 FG respectively. The corresponding 3-D models are shown as Figure 4K,L. The reconstructed artificial flap is labeled in orange. **11. Potential Application of CAD Models with Adjusting Contours in Prospective Brain Sciences**  
In clinical practice, the profound outward herniation of brain tissues, along with the scalp, will take place after the performance of a DC procedure, due to injury-driven brain swelling. Under such situations, microdynamics of the cerebrum can be a subject of concern. Gaining better understanding of the possible mechanisms as follows will help to interpret how the brainstem can be protected during the DC procedure. How much are brain volumes able to be shifted outside the skull bone, which eventually prevents the brainstem from being compromised? How large an area of the skull defects can facilitate more accommodation of an injury-driven swollen brain? Where does interaction exist between i and ii? The above-mentioned issues are likely to be resolved via quantitative volumetric assessment and advanced regression calculation.