This study aimed to validate apparent diffusion coefficient (ADC) values and thresholds to predict poor neurological outcomes in out-of-hospital cardiac arrest (OHCA) survivors by quantitatively analysing the ADC values via brain magnetic resonance imaging (MRI). This observational study used prospectively collected data from two tertiary academic hospitals. The derivation cohort comprised 70% of the patients randomly selected from one hospital, whereas the internal validation cohort comprised the remaining 30%. The external validation cohort used the data from another hospital, and the MRI data were restricted to scans conducted at 3 T within 72–96 h after an OHCA experience. We analysed the percentage of brain volume below a specific ADC value at 50-step intervals ranging from 200 to 1200 × 10–6 mm2/s, identifying thresholds that differentiate between good and poor outcomes. Poor neurological outcomes were defined as cerebral performance categories 3–5, 6 months after experiencing an OHCA. A total of 448 brain MRI scans were evaluated, including a derivation cohort (n = 224) and internal/external validation cohorts (n = 96/128, respectively). The proportion of brain volume with ADC values below 450, 500, 550, 600, and 650 × 10–6 mm2/s demonstrated good to excellent performance in predicting poor neurological outcomes in the derivation group (area under the curve [AUC] 0.89–0.91), and there were no statistically significant differences in performances among the derivation, internal validation, and external validation groups (all P > 0.5). Among these, the proportion of brain volume with an ADC below 600 × 10–6 mm2/s predicted a poor outcome with a 0% false-positive rate (FPR) and 76% (95% confidence interval [CI] 68–83) sensitivity at a threshold of > 13.2% in the derivation cohort. In both the internal and external validation cohorts, when using the same threshold, a specificity of 100% corresponded to sensitivities of 71% (95% CI 58–81) and 78% (95% CI 66–87), respectively. In this validation study, by consistently restricting the MRI types and timing during quantitative analysis of ADC values in brain MRI, we observed high reproducibility and sensitivity at a 0% FPR. Prospective multicentre studies are necessary to validate these findings.

中文翻译：

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表观扩散系数的定量分析以预测心脏骤停幸存者的神经学预后：观察推导和内部-外部验证研究

本研究旨在通过脑磁共振成像 (MRI) 定量分析 ADC 值，验证表观扩散系数 (ADC) 值和阈值，以预测院外心脏骤停 (OHCA) 幸存者的不良神经学结果。这项观察性研究使用了从两家三级学术医院前瞻性收集的数据。衍生队列包含从一家医院随机选择的 70% 患者，而内部验证队列包含剩余的 30%。外部验证队列使用另一家医院的数据，MRI 数据仅限于 OHCA 经历后 72-96 小时内以 3 T 进行的扫描。我们以 200 至 1200 × 10-6 mm2/s 的 50 步间隔分析了低于特定 ADC 值的脑体积百分比，确定了区分好结果和差结果的阈值。不良神经学结果被定义为经历 OHCA 后 6 个月的大脑表现类别 3-5。总共评估了 448 个脑部 MRI 扫描，包括衍生队列（n = 224）和内部/外部验证队列（分别为 n = 96/128）。 ADC 值低于 450、500、550、600 和 650 × 10–6 mm2/s 的脑体积比例在预测推导组的不良神经学结果方面表现出良好至优异的性能（曲线下面积 [AUC] 0.89– 0.91），推导组、内部验证组和外部验证组之间的性能没有统计学上的显着差异（均 P > 0.5）。其中，ADC 低于 600 × 10–6 mm2/s 的脑体积比例预测结果较差，假阳性率 (FPR) 为 0% 和 76%（95% 置信区间 [CI] 68–83）推导队列中的敏感性阈值 > 13.2%。在内部和外部验证队列中，当使用相同阈值时，100% 的特异性对应的灵敏度分别为 71% (95% CI 58–81) 和 78% (95% CI 66–87)。在这项验证研究中，通过在脑部 MRI 中的 ADC 值定量分析过程中持续限制 MRI 类型和时间，我们观察到 0% FPR 时的高再现性和灵敏度。需要进行前瞻性多中心研究来验证这些发现。