Background Field-cycling imaging (FCI) is a new technology developed at the University of Aberdeen that measures change in T1 relaxation time constant of tissues over a range of low magnetic field strengths (0.2-200 mT) by rapidly switching between different fields during the pulse sequence. This provides new sources of contrast, including some invisible to clinical MRI scanners, and may be a useful alternative imaging modality for stroke. Purpose To test whether a prototype whole-body FCI scanner can be used to identify infarct regions in patients with subacute ischemic stroke. Materials and Methods This prospective study screened consecutive adult patients admitted to a single center stroke unit from February 2018 to March 2020 and April to December 2021. Included participants with confirmed ischemic stroke underwent FCI 1-6 days after ictus. FCI scans were obtained at four to six evolution fields between 0.2 mT and 0.2 T, with five evolution times from 5 to 546 msec. T1 maps were generated. The Wilcoxon signed-rank test was used to compare infarct region and contralateral unaffected brain, and Spearman rank correlation was used to examine associations between infarct to contralateral tissue contrast ratio and field strengths. Two independent readers blinded to clinical images rated the FCI scans. Results Nine participants (mean age, 62 years ± 16 [SD]; all male) successfully completed FCI. FCI scans below 0.2 T exhibited hyperintense T1 regions corresponding to the infarct region identified at baseline imaging, visually confirmed with 86% interrater agreement (Cohen κ = 0.69). Infarct to contralateral tissue contrast ratio increased as magnetic field decreased between 0.2 mT and 0.2 T (r[24] = -0.68; P < .001). T1 dispersion slopes differed between infarct and unaffected tissues (median, 0.23 [IQR, 0.18-0.37] vs 0.35 [IQR, 0.27-0.43]; P = .03). Conclusion Whole-brain FCI can be used to identify subacute ischemic stroke by T1 relaxation mechanisms at field strengths as low as 0.2 mT. Research Registry no. 1813 Published under a CC BY 4.0 license. Supplemental material is available for this article.

中文翻译：

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用于识别 0.2 T 以下的轻微缺血性中风的场循环 MRI。


背景场循环成像（FCI）是阿伯丁大学开发的一项新技术，通过在低磁场强度（0.2-200 mT）范围内快速切换不同磁场来测量组织 T1 弛豫时间常数的变化。脉冲序列。这提供了新的对比来源，包括一些临床 MRI 扫描仪不可见的对比来源，并且可能是中风的有用的替代成像方式。目的 测试原型全身 FCI 扫描仪是否可用于识别亚急性缺血性卒中患者的梗塞区域。材料和方法 这项前瞻性研究筛选了 2018 年 2 月至 2020 年 3 月以及 2021 年 4 月至 2021 年 12 月入住单中心卒中病房的连续成年患者。其中包括确诊为缺血性卒中的参与者，他们在发作后 1-6 天接受了 FCI。 FCI 扫描在 0.2 mT 和 0.2 T 之间的四到六个演化场获得，五个演化时间从 5 到 546 毫秒。 T1 地图已生成。 Wilcoxon 符号秩检验用于比较梗塞区域和对侧未受影响的大脑，Spearman 等级相关用于检查梗塞与对侧组织对比度和场强之间的关联。两名对临床图像不知情的独立读者对 FCI 扫描进行了评分。结果 9 名参与者（平均年龄，62 岁±16 [SD]；均为男性）成功完成 FCI。低于 0.2 T 的 FCI 扫描显示出与基线成像时识别的梗塞区域相对应的高信号 T1 区域，视觉上确认了 86% 的受试者间一致性（Cohen κ = 0.69）。当磁场在 0.2 mT 和 0.2 T 之间降低时，梗塞与对侧组织的对比度增加 (r[24] = -0.68；P < .001)。 梗塞组织和未受影响组织之间的 T1 弥散斜率不同（中位数，0.23 [IQR，0.18-0.37] 与 0.35 [IQR，0.27-0.43]；P = 0.03）。结论 全脑 FCI 可通过场强低至 0.2 mT 的 T1 弛豫机制来识别亚急性缺血性卒中。研究登记号1813 根据 CC BY 4.0 许可证发布。本文提供了补充材料。