BACKGROUND A simple dimensionless aneurysm number ($An$), which depends on geometry and flow pulsatility, was previously shown to distinguish the flow mode in intracranial aneurysms (IA): vortex mode with a dynamic vortex formation/evolution if $An > 1$, and cavity mode with a steady shear layer if $An < 1$. OBJECTIVE To hypothesize that $An\ > \ 1$ can distinguish rupture status because vortex mode is associated with high oscillatory shear index, which, in turn, is statistically associated with rupture. METHODS The above hypothesis is tested on a retrospective, consecutively collected database of 204 patient-specific IAs. The first 119 cases are assigned to training and the remainder to testing dataset. $An$ is calculated based on the pulsatility index (PI) approximated either from the literature or solving an optimization problem (denoted as$\ \widehat {PI}$). Student's t-test and logistic regression (LR) are used for hypothesis testing and data fitting, respectively. RESULTS $An$ can significantly discriminate ruptured and unruptured status with 95% confidence level (P < .0001). $An$ (using PI) and $\widehat {An}$ (using $\widehat {PI}$) significantly predict the ruptured IAs (for training dataset $An\!:\ $AUC = 0.85, $\widehat {An}\!:\ $AUC = 0.90, and for testing dataset $An\!:\ $sensitivity = 94%, specificity = 33%, $\widehat {An}\!:\ $sensitivity = 93.1%, specificity = 52.85%). CONCLUSION $An > 1$ predicts ruptured status. Unlike traditional hemodynamic parameters such as wall shear stress and oscillatory shear index, $An$ has a physical threshold of one (does not depend on statistical analysis) and does not require time-consuming flow simulations. Therefore, $An$ is a simple, practical discriminator of IA rupture status.

中文翻译：

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一个简单的流量分类参数可以区分颅内动脉瘤的破裂状态

背景 一个简单的无量纲动脉瘤数 ($An$) 取决于几何形状和血流脉动，以前被证明可以区分颅内动脉瘤 (IA) 中的血流模式：如果 $An > 1$，则具有动态涡流形成/演化的涡流模式，如果 $An < 1$，则具有稳定剪切层的腔模式。目的假设$An\ > \ 1$ 可以区分破裂状态，因为涡模式与高振荡剪切指数相关，而后者又与破裂在统计上相关。方法 上述假设在一个回顾性的、连续收集的 204 名患者特异性 IAs 数据库中进行检验。前 119 个案例分配给训练，其余分配给测试数据集。$An$ 是根据从文献或解决优化问题（表示为 $\ \widehat {PI}$）中近似得出的脉动指数 (PI) 计算得出的。学生 t 检验和逻辑回归 (LR) 分别用于假设检验和数据拟合。结果 $An$ 可以以 95% 的置信水平 (P < .0001) 显着区分破裂和未破裂状态。$An$（使用 PI）和 $\widehat {An}$（使用 $\widehat {PI}$）显着预测破裂的 IA（对于训练数据集 $An\!:\ $AUC = 0.85，$\widehat {An }\!:\ $AUC = 0.90，对于测试数据集 $An\!:\ $敏感性 = 94%，特异性 = 33%，$\widehat {An}\!:\ $敏感性 = 93.1%，特异性 = 52.85 %）。结论 $An > 1$ 预测破裂状态。不同于传统的血流动力学参数，如壁面剪切应力和振荡剪切指数，$An$ 的物理阈值为 1（不依赖于统计分析）并且不需要耗时的流动模拟。因此，$An$ 是 IA 破裂状态的一个简单实用的判别器。