## 3 Results  
The inclusion criteria were met by 113 patients. Five patients with posterior circulation occlusion were excluded. None of the patients were excluded due to technically inadequate CTA. Finally, 108 participants were included in the study. Their mean age was 70 years (\(\pm\)12.6 years), and 55 (50.9%) were females.  
The neuroradiologist found LVOs in 70 (64.8%) cases, of which 45 (41.7%) were proximal, and 25 (23.1%) were distal occlusions. In all 70 cases with LVOs detected by a neuroradiologist, MT was subsequently performed. Initial DSA series preceding MT confirmed the presence of LVOs detected by a neuroradiologist with CTA in all cases without false positive ones. This gave the specificity of 100% for interventional neuroradiologist.  
The mean time gap from CTA to the initial DSA series was 24 min (\(\pm\)8 min). In patients treated with intravenous thrombolysis, the initial DSA series showed migration of thrombus from the proximal to the distal part of M1 in two cases and from the proximal to the distal part of M2 in one case.  
Medical students detected 63 (58.3%) LVOs, while e-CTA revealed 49 (45.4%) LVOs. The findings are presented in detail in Table 1.  
Out of the 70 LVOs, 23 (32.9%) were missed by e-CTA, from which 7 out of 45 (15.6%) were proximal and 16 out of 25 (64.0%) were distal. Examples of proximal and distal LVOs detected by e-CTA are illustrated in Figure 1.  
This gave the overall sensitivity for e-CTA of 0.67 (95% CI 0.55-0.78), 0.84 (95% CI 0.71-0.94) for proximal LVOs, and 0.36 (95% CI 0.18-0.57) for distal LVOs. Overall specificity,  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Occlusion Localization**}} & \multicolumn{2}{c}{**Neuoradiologist**} & \multicolumn{2}{c}{**e-CTA**} & \multicolumn{2}{c}{**Medical Students**} \\  & **(n = 70)** & **(n = 49)** & **(n = 63)** \\ \hline \multirow{3}{*}{Proximal} & ICA & 14 & 13 & 8 \\ \cline{2-5}  & ICA+MCA-M1 & 7 & 6 & 9 \\ \cline{1-1} \cline{2-5}  & MCA-M1 & 24 & 22 & 36 \\ \hline Distal & M2 & 25 & 8 & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Distribution of LVOs detected by neuroradiologist, e-CTA and medical students.  
Figure 1: CTAs of stroke patients with LVOs correctly detected by e-CTA. (**A**) e-CTA detected proximal LVO of the right MCA-M1 (red circle); (**B**) e-CTA detected distal LVO of the left MCA-M2 (red circle).  
PPV, NPV and accuracy for e-CTA were 0.95 (95%CI 0.82-0.99), 0.96 (95%CI 0.86-0.99), 0.61 (95%CI 0.47-0.73), and 0.77 (95%CI 0.68-0.84), respectively. The mean processing time was 96 seconds (\(\pm\)23 s).  
In total, 17 out of 70 (24.3%) LVOs were missed by the medical students, from which 3 out of 45 (6.7%) were proximal, and 14 out of 25 (56.0%) were distal. The medical students achieved the overall sensitivity of 0.76 (95% CI 0.64-0.85), 0.93 (95% CI 0.82-0.99) for proximal LVOs, and 0.44 (95% CI 0.24-0.65) for distal LVOs. Students reached the overall specificity, PPV, NPV, and accuracy of 0.74 (95% CI 0.57-0.87), 0.84 (95% CI 0.73-0.92), 0.62 (95% CI 0.47-0.76), and 0.75 (95% CI 0.66-0.83), respectively.  
Table 2 summarizes the performance of e-CTA and medical students.  
Interobserver agreement between the neuroradiologist and medical students was 0.47 (Cohen's kappa) overall, 0.68 for proximal LVOs and 0.18 for distal LVOs. Levels of interobserver agreement between neuroradiologist and e-CTA were 0.55, 0.78, and 0.34, respectively. Finally, respective levels of interobserver agreement between medical students and e-CTA were 0.45, 0.57, and 0.03.