# Assessment of Cranial Deformation Indices by Automatic Smartphone-Based Photogrammetric Modelling
## 4 Discussion  
Many papers can be found in the literature comparing results achieved with different solutions [5], direct calliper measures [6; 17], orthogonal photography [26], CT [27], and 3D photogrammetry images [17; 27; 28; 29; 30]. They permit some general conclusions to be drawn: first, calliper measurements are a bit smaller (1-4 mm [17], around 2% [5]) than the digital photogrammetric results, possibly due to the pressure of the callipers and/or the use of skullcaps for photogrammetric solutions [17]; second, although CT yields the best solution [6], it is not recommended since the patient has to be sedated [5], and it constitutes \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Cranial Parameter**} & \multirow{2}{*}{**Value**} & **Uncertainty** & **Uncertainty** & **Uncertainty** & **Uncertainty** & **Uncertainty** \\  & & **(Meas. Accuracy** & **(Meas. Accuracy** & **(Meas. Accuracy** & **(Meas. Accuracy** & **from the** \\  & & **0.5 mm)** & **0.75 mm)** & **1.0 mm)** & **1.5 mm)** & **54 Measured Models** \\ \hline _OCLR_ (\%) & 100 & **0.7** & 1.0 & 1.4 & 2.0 & 0.3 \\ _CI_ (\%) & 97 & **0.7** & 1.1 & 1.4 & 2.1 & 0.7 \\ _TI_ (\%) & 68 & 0.5 & 0.8 & 1.1 & **1.6** & 1.4 \\ _MI_ (\%) & 54 & **0.7** & 1.0 & 1.4 & 2.0 & 0.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Cranial deformation indices along with their corresponding uncertainties for different values of measurement accuracy (0.5, 0.75, 1, and 1.5 mm). Experimental uncertainties derived from the 54 measured models are provided in the last column. The bold values highlight the closest largest uncertainties. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Cranial Parameter**} & \multirow{2}{*}{**Value**} & **Uncertainty** & **Uncertainty** & **Uncertainty** & **Uncertainty** & **Uncertainty** \\  & & **(Meas. Accuracy** & **(Meas. Accuracy** & **(Meas. Accuracy** & **(Meas. Accuracy** & **from the** \\  & & **0.5 mm)** & **0.75 mm)** & **1.0 mm)** & **1.5 mm)** & **54 Measured Models** \\ \hline _CV_ (mL) & 464 & 10 & 14 & 19 & **29** & 25.8 \\ _CP_ (mm) & 390 & **2** & 3 & 4 & 7 & 2.0 \\ _DPaP_ (mm) & 106.4 & 0.7 & **1.1** & 1.4 & 2.1 & 0.8 \\ \(d\) (mm) & 117.1 & **0.7** & 1.1 & 1.4 & 2.1 & 0.7 \\ \(c\) (mm) & 121.3 & 0.7 & **1.1** & 1.4 & 2.1 & 0.8 \\ \(a\) (mm) & 146.2 & 0.7 & 1.1 & 1.4 & **2.1** & 1.9 \\ \(b\) (mm) & 146.3 & 0.7 & 1.1 & 1.4 & **2.1** & 1.8 \\ \(a\) (mm) & 67.3 & 0.6 & 0.9 & **1.2** & 1.8 & 1.1 \\ \(b\) (mm) & 65.9 & 0.6 & 0.9 & **1.2** & 1.8 & 1.2 \\ \(a\) (mm) & 78.9 & 0.6 & 0.9 & **1.2** & 1.8 & 1.0 \\ \(b\) (mm) & 80.4 & 0.6 & 0.9 & **1.2** & 1.8 & 0.8 \\ _AI_ (mm) & 0 & **1.0** & 1.5 & 2.0 & 3.0 & 0.5 \\ _AI_ (mm) & 1 & **0.9** & 1.3 & 1.7 & 2.6 & 0.5 \\ _AI_ (mm) & -2 & **0.9** & 1.3 & 1.7 & 2.6 & 0.5 \\ _Perimeter30_ (mm) & 3 & **1.6** & 2.4 & 3.1 & 4.7 & 1.2 \\ _FA_ (deg) & 114.4 & **1.4** & 2.1 & 2.8 & 4.2 & 1.1 \\ Global (mm) & 2.1 & **0.7** & 1.1 & 1.4 & 2.1 & 0.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Cranial anthropometric parameters along with their corresponding uncertainties for different values of measurement accuracy (0.5, 0.75, 1, and 1.5 mm). Experimental uncertainties derived from the 54 measured models are provided in the last column. The bold values highlight the closest largest uncertainties. an avoidable exposure to radiation that entails a higher risk of malignancies in later life; third, other solutions, such as orthogonal photography [6] or, better, 3D photogrammetry, since it is more flexible in terms of image acquisition (\"fast, easy, and independent of the examiner\" [27]) are preferred. However, to the authors' understanding, nothing has been written about both the accuracy and uncertainty in the derived anthropometric cranial parameters and indices, which are important estimates for diagnosing cranial deformations by medical specialists such as paediatric neurosurgeons and paediatricists.