# Cranial Implant Design Applying Shape-Based Interpolation Method via Open-Source Software
## 4 Discussion  
The 3-matic software and MITK were both used to design patient-specific cranial implants. The implant designed using MITK was produced applying the shape-based interpolation method with two different techniques, namely the tenth and fifth slices segmentation. HD and DSC analyses comparing all three designs (produced using the 3-matic, MITK tenth slice, and MITK fifth slice) showed no significant differences among them. The Kruskal-Wallis analyses on the surface area and volume of the patient-specific implants also showed no significant differences. Based on these findings, the patient-specific cranial implants produced using the gold standard 3-matic software and open-source MITK are comparable. It was reported that HD values less than 3 mm and DSC values above 0.80 were considered adequate [18]. It was also reported that the DSC value of 0.86 was considered \begin{table}
\begin{tabular}{c c c} \hline \hline
**Cranial Implant** & **3-Matic vs. MITK Tenth Slice** & **3-Matic vs. MITK Fifth Slice** \\ \hline
1 & 0.456 & 0.355 \\
2 & 0.423 & 0.271 \\
3 & 0.148 & 0.097 \\
4 & 0.480 & 0.342 \\
5 & 0.106 & 0.002 \\
6 & 0.333 & 0.145 \\
7 & 0.425 & 0.260 \\
8 & 0.116 & 0.016 \\
9 & 0.020 & 0.024 \\
10 & 0.301 & 0.017 \\ \hline \hline
**Mean (SD)** & **0.281 (0.17)** & **0.152 (0.14)** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Geometric analyses (HD) of cranial implants. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Cranial Implant** & **3-Matic vs. MITK Tenth Slice** & **3-Matic vs. MITK Fifth Slice** \\ \hline
1 & 0.856 & 0.888 \\
2 & 0.776 & 0.891 \\
3 & 0.879 & 0.894 \\
4 & 0.788 & 0.825 \\
5 & 0.898 & 0.922 \\
6 & 0.884 & 0.907 \\
7 & 0.882 & 0.912 \\
8 & 0.794 & 0.871 \\
9 & 0.916 & 0.931 \\
10 & 0.837 & 0.925 \\ \accurate [19]. The HD value from this study for 3-matic vs. MITK was 0.28 mm (every 10 th slice) and 0.15 mm (every 5 th slice), suggesting that the cranial implants reconstructed using MITK software are accurate or similar to the gold standard. The cranial implants reconstructed using the shape-based interpolation method via open-source MITK software have a DSC value of 0.851 (every 10 th slice) and 0.897 (every 5 th slice) when analysed against the gold standard. This showed that the cranial implants created using the shape-based interpolation method via MITK on every tenth slice and every fifth were 85.1% and 89.7%, similar to the gold standard, respectively. The patient-specific cranial implants were successfully designed using commercial 3-matic software and an open-source MITK software applying a shape-based interpolation method; both showed high similarity in the surface area and volume. The measurements demonstrated no differences using HD analyses and good similarity using DSC analyses for all ten patient-specific cranial implants. The conclusion from these findings was that designs created using open-source software provided similar results to commercial software. In conclusion, this study confirmed that the shape-based interpolation method via open-source MITK software gave comparable results in the design of patient-specific cranial implants compared to the commercial gold standard 3-matic software. This confirms that the simpler shape-based interpolation method could be used to design patient-specific cranial implants instead of complicated CAD software. The inclusion of this software in a clinical setting would save clinicians' time in pre-operative planning and the cost in patient management. Conceptualisation, J.Y.A., A.M.A. and L.P.H. ; methodology, J.Y.A. ; software, J.Y.A. ; validation, H.H., A.H. and Z.A.R. ; formal analysis, J.Y.A. ; investigation, J.Y.A. ; resources, Z.A.R. ; data curation, J.Y.A. ; writing--original draft preparation, J.Y.A. ; writing--review and editing, J.Y.A. and A.M.A. ; visualization, J.Y.A. ; supervision, Z.A.R., A.H. and H.H. ; project administration, J.Y.A. ; funding acquisition, J.Y.A. All authors have read and agreed to the published version of the manuscript.