## 3 Results
### MARS-MMA Scoring System  
A model with the variables CVR impairment, arterial vessel wall contrast enhancement and positive Ivy sign yielded a significant prediction of a severe [15O]water PET CPR impairment (see Table 3). Based on the optimized rounded weights for each factor (CVR impairment = 4, arterial vessel wall contrast enhancement = 3, Ivy sign = 2), a new scoring system was created (see Table 4). As the new scoring system consisted of only MRI-based components, we called it _MRI-Based Assessment of Risk of Stroke in Moyamoya Angiopathy_ (MARS-MMA). Figure 2: ROC curves of the PIRAMID components, the PIRAMID score and its grade with regard to the prediction of neurological symptomatology. In the evaluation of the territories of the internal carotid arteries (**a**), the AUCs of the PIRAMID score (0.749 *) and grade (0.724 *) were higher than the AUCs of all individual parameters (modified Suzuki Score (mSS) (0.692 *), impaired collateralization (0.638 *), prior infarcts (0.708 *), cerebrovascular reactivity (CVR) (0.646 *)). This was also evident in the evaluation of the territories of the anterior and the middle cerebral arteries (**b**): PIRAMID score (0.784 *), PIRAMID grade (0.745 *), mSS (0.654 *), impaired collateralization (0.654 *), prior infarcts (0.722 *), CVR (0.716 *)). * Confidence intervals not given since multiple territories (2 or 4) per patient were evaluated. The MARS-MMA grade stratification with the following thresholds revealed the highest AUC (0.855): grade 1, 0 points; grade 2, 2-5 points; grade 3, 6-9 points (see Tables 5 and S2). Comparison of the PIRAMID Score and the MARS-MMA Score Regarding the Predictability of PET CPR Impairment on [15]Water  
The weights of the adapted PIRAMID score can be seen in Table 6. The AUC of the MARS-MMA score (0.859) and the AUC of the MARS-MMA grade (0.855) were higher than the AUCs of all individual components of the score (see Figure 3). The comparison of the two scoring systems revealed a higher AUC for the MARS-MMA score than the adapted PIRAMID score (0.859 versus 0.827) (see Figure 3) and a lower AIC for the MARS-MMA score than the adapted PIRAMID score (140 versus 146). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Variable** & **Odds Ratio** & \(p\)**Value** & \begin{tabular}{c} **95\% Confidence** \\ **Interval** \\ \end{tabular} & \begin{tabular}{c} **Regression** \\ **Coefficient** \\ \end{tabular} \\ \hline mSS & 1.655 & 0.312 & 0.628–4.397 & 0.504 \\ \hline Collaterals & 0.913 & 0.856 & 0.342–2.435 & \(-\)0.091 \\ \hline Prior infarct & 2.812 & 0.022 & 1.160–6.818 & 1.034 \\ \hline bh-fMRI CVR & \multirow{2}{*}{7.289} & \multirow{2}{*}{\begin{tabular}{c} \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} \end{tabular} } \\ impairment \textgreater{} 50\% & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of the binary logistic regression analysis with [15]Water PET cerebral perfusion reserve impairment as the dependent variable and block entry of the independent variables. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Variable** & **Points** \\ \hline Breath-hold fMRI cerebrovascular reactivity impairment (CVR) of & & \\ at least 50\% compared to the cerebellar CVR response & & \\ \hline Arterial vessel wall contrast enhancement & & \\ \hline Presence of Ivy sign on FLAIR images & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The MARS-MMA scoring system. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Variable** & **Odds Ratio** & \(p\)**Value** & \
\begin{tabular}{c} **95\% Confidence** \\ **Interval** \\ \end{tabular} &
\begin{tabular}{c} **Regression** \\ **Coefficient** \\ \end{tabular} \\ \hline bh-fMRI CVR & 9.300 & \textless{}0.001 & 3.702–23.361 & 2.230 \\ \hline Arterial vessel wall contrast enhancement & 4.382 & 0.002 & 1.752–10.961 & 1.477 \\ \hline Ivy sign & 3.167 & 0.012 & 1.291–7.766 & 1.153 \\ \hline \hline \end{tabular}
\end{table}