## 4 Discussion and Conclusions
The commercial 3 MensioTM (Vascular Imaging, Bilthoven, The Netherlands) is a dedicated sizing software typically used for planning EVAR, treatment of thoracic aneurysms (TEVAR) or placement of fenestrated stents (FEVAR) [14; 15]. Although it offers automatic vessel segmentation and center lumen line detection as well as the assessment of vessel tortuosity with respect to length measurements, the aneurysm volume calculation still remains quite time-consuming and operator-dependent, requiring a lot of \"manual\" interaction by the user, e.g., for the selection of fiduciary markers along the aneurysm shape on bi-dimensional images). Sometimes the marker selection has to be repeated for more than one 2D projection, and for each computation of the various aneurysm volumes of interest for preoperative planning (Figure 7). Moreover, the estimation of endoluminal FV available for SE with coils cannot be directly provided by the software, but the user has to calculate it offline by subtracting the approximated endograft volume to the calculated AAA lumen volume (Figure 7d). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Software tools**} \\ \hline
**Feature** & **EVAR-eaSE** & **3 Mensio** & **AngioSuite** & **AngioCalc** & **Leonardo** \\ \hline
**Main field of application** & Vascular & Vascular & Neurovascular & Neurovascular & Neurovascular \\ \hline
**Imaging source** & CTA & CTA & Biplane angiograms & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & & & & & \\  & & YES & & & & \\  & & (semi-automatic & manual & & performed from 2D & \\
**Image segmentation** & of AAA total & selection of & aneurysm & Not applicable & contour in \\  & and AAA total & fiduciary & measurements, 3D & & every slice in \\  & & & markers along & measurements and & axial views) & \\  & & the aneurysm & fiduciary markers & & [16] & \\  & & & shape) [14; 15] & & & YES & \\ \hline
**Computation of aneurysm volumes** & YES & YES & YES & & \\  & & & & & (shape model selection & \\  & & & & & and input of 2D & YES \\  & & & & & aneurysm & \\  & & & & & measurements) & \\ \hline
**Input of endograft and/or coils** & YES & NO & YES & YES & NO \\  & & & & & & \\  & & & & & \\  & & & & & & \\  & & & & & \\ \hline
**Computation of planning parameters** & YES & YES & (packing density) & YES & \\  & & & & & (packing density) & NO \\  & & & & & [17] & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparative table of EVAR-eaSE with other available software tools. Vessel segmentation in 3 Mensio strictly depends on manual selection of the fiduciary markers on the external sac profile, while EVAR-eaSE uses an automatic seeded region grow algorithm starting from a clicked seed voxel within the volume (Figure 8); this different approach may explain the small differences found for the two software in the computed volumes for the same AAA case (Table 5). Among the other available software applications, mainly intended for neuro-interventionalists, the AngioCalc is an online calculator that estimates cerebral and peripheral aneurysm volume and percent packing volume after selection within a list of commercial neurovascular coils [16; 17]. Its major limitation is in the use of ellipsoid and multi-lobular geometric models for approximating the aneurysm, that do not take into account the real irregularity of patient-specific aneurysm anatomies. Another system (AngioSuite, Cascade Medical, Knoxville, TN, USA) is able to calculate aneurysm volumes from biplane angiograms after calibration from known fiduciary markers, in a good accurate way [17]. Finally, with Leonardo workstation (Siemens, Erlangen, Germany) the aneurysm dimensions and volumes can be analyzed and computed starting from three-dimensional rotational angiograms windowed to the best visual appearance, but results are not particularly accurate [16; 17]. EVAR-eaSE software achieves a good level of accuracy in 3D aneurysm volume reconstruction and calculation, as demonstrated by the performed tests on radiological phantoms.