Supplementary Material for: Possible Influence of Ethnicity on CT Perfusion Parameter Thresholds in Acute Ischemic Stroke

Introduction
Tissue at risk, as estimated by CT perfusion utilizing Tmax+6, correlates with final infarct volume (FIV) in acute ischemic stroke (AIS) without reperfusion. Tmax thresholds are derived from Western ethnic populations but not from ethnic Asian populations. We aimed to investigate the influence of ethnicity on Tmax thresholds.

Methods
From a clinical-imaging registry of Australian and Indonesian stroke patients, we selected a participant subgroup with the following inclusion criteria: AIS under 24 hours and absence of reperfusion therapy. Clinical data included demographics, time metrics, stroke severity, premorbid, and 3-month Modified Rankin Score. Baseline CTP and MRI <72 hours were performed. Volumes of Tmax utilizing different thresholds and final infarct volumes (FIV) were calculated. Spearman correlation was used to evaluate relationship involving ordinal variables and calculate the optimal Tmax threshold against FIV in both populations.

Results
Two hundred patients were included in the study sample 100 in Jakarta and 100 in Geelong. The median National Institutes Health Stroke Scale (IQR) were 6(3-11) and 3(1-5), respectively. The median Tmax+6(IQR) was 0 (0-46.5) in Jakarta group and 0(0-7.5) in Geelong group. The median FIV(IQR) was 0 (0-30.5) and 0 (0-5.5). Tmax +8s in Jakarta population against FIV showed Spearman’s coefficient =0.72, representing the optimal Tmax threshold. Tmax+6s showed Spearman’s coefficient =0.51 against FIV in the Geelong population.

Conclusions
Tmax thresholds approximating FIV were possibly different in the Asian when compared with the non-Asian populations. Future studies are required to extend and confirm the validity of our findings.

### 研究背景
采用Tmax+6阈值的CT灌注（CT perfusion, CTP）评估的缺血风险脑组织，与未接受再灌注治疗的急性缺血性脑卒中（acute ischemic stroke, AIS）患者的最终梗死体积（final infarct volume, FIV）具有相关性。当前Tmax阈值多基于西方人群数据推导得出，尚无亚洲人群的相关研究依据。本研究旨在探究种族因素对Tmax阈值的影响。

### 研究方法
本研究从澳大利亚与印度尼西亚脑卒中患者的临床影像登记数据库中，筛选符合以下纳入标准的受试者亚组：发病24小时内确诊急性缺血性脑卒中，且未接受再灌注治疗。收集的临床资料包括人口学特征、时间相关指标、脑卒中严重程度、病前功能状态以及发病3个月时的改良Rankin量表（Modified Rankin Score, mRS）评分。所有受试者于发病72小时内完成基线CT灌注（CTP）及磁共振成像（magnetic resonance imaging, MRI）检查。计算不同Tmax阈值下的脑组织体积及最终梗死体积（FIV）。采用Spearman相关分析评估有序分类变量间的相关性，并分别在两个人群中计算与最终梗死体积（FIV）匹配的最优Tmax阈值。

### 研究结果
本研究共纳入200例受试者，其中雅加达组100例，吉朗组100例。两组的美国国立卫生研究院卒中量表（National Institutes of Health Stroke Scale, NIHSS）评分中位数（四分位间距，interquartile range, IQR）分别为6（3~11）与3（1~5）。雅加达组与吉朗组的Tmax+6中位数（四分位间距）分别为0（0~46.5）与0（0~7.5）。两组的最终梗死体积（FIV）中位数（四分位间距）分别为0（0~30.5）与0（0~5.5）。雅加达人群中，Tmax+8s阈值与最终梗死体积（FIV）的Spearman相关系数ρ=0.72，为该人群的最优Tmax阈值；吉朗人群中，Tmax+6s阈值与最终梗死体积（FIV）的Spearman相关系数ρ=0.51。

### 研究结论
与非亚裔人群相比，亚裔人群中与最终梗死体积（FIV）匹配的Tmax阈值可能存在差异。未来需开展进一步研究以拓展样本范围并验证本研究结果的有效性。