Centre for Biomedical Engineering, Indian Institute of Technology Delhi, New Delhi, India.
Philips Health System, Philips India Limited, Gurugram, India.
NMR Biomed. 2021 Jul;34(7):e4526. doi: 10.1002/nbm.4526. Epub 2021 Apr 20.
In acute-ischemic-stroke patients, penumbra assessment plays a significant role in treatment outcome. MR perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) mismatch ratio can provide penumbra assessment. Recently reported studies have shown the potential of susceptibility-weighted imaging (SWI) in the qualitative assessment of penumbra. We hypothesize that quantitative penumbra assessment using SWI-DWI can provide an alternative to the PWI-DWI approach and this can also reduce the overall scan-time. The purpose of the current study was to develop a framework for accurate quantitative assessment of penumbra using SWI-DWI and its validation with PWI-DWI-based quantification. In the current study, the arterial-spin-labelling (ASL) technique has been used for PWI. This retrospective study included 25 acute-ischemic-stroke patients presenting within 24 hours of the last noted baseline condition of stroke onset. Eleven patients also had follow-up MRI within 48 hours. MRI acquisition comprised DWI, SWI, pseudo-continuous-ASL (pCASL), FLAIR and non-contrast-angiography sequences. A framework was developed for the enhancement of prominent hypo-intense vein signs followed by automatic segmentation of the SWI penumbra ROI. Apparent-diffusion-coefficient (ADC) maps and cerebral-blood-flow (CBF) maps were computed. The infarct core ROI from the ADC map and the ASL penumbra ROI from CBF maps were segmented semiautomatically. The infarct core volume, SWI penumbra volume (SPV) and pCASL penumbra volume were computed and used to calculate mismatch ratios and . The Dice coefficient between the SWI penumbra ROI and ASL penumbra ROI was 0.96 ± 0.07. correlated well (r = 0.90, p < 0.05) with , which validates the hypothesis of accurate penumbra assessment using the SWI-DWI mismatch ratio. Moreover, a significant association between high SPV and the presence of vessel occlusion in the MR angiogram was observed. Follow-up data showed salvation of penumbra tissue (location and volumes predicted by proposed framework) by treatments. Additionally, functional-outcome analysis revealed 93.3% of patients with > 1 benefitted from revascularization therapy. Overall, the proposed automated quantitative assessment of penumbra using the SWI-DWI mismatch ratio performs equivalently to the ASL PWI-DWI mismatch ratio. This approach provides an alternative to the perfusion sequence required for penumbra assessment, which can reduce scan time by 17% for the protocol without a perfusion sequence.
在急性缺血性中风患者中，半影区评估在治疗结果中起着重要作用。磁共振灌注加权成像（PWI）和弥散加权成像（DWI）不匹配比可以提供半影区评估。最近的研究报告表明，磁化率加权成像（SWI）在半影区的定性评估中有潜力。我们假设使用 SWI-DWI 进行定量半影区评估可以替代 PWI-DWI 方法，并且还可以减少总扫描时间。本研究的目的是开发一种使用 SWI-DWI 进行准确定量半影区评估的框架，并通过基于 PWI-DWI 的定量验证。在本研究中，动脉自旋标记（ASL）技术用于 PWI。这项回顾性研究包括 25 名在中风发病的最后记录的基线状态后 24 小时内出现的急性缺血性中风患者。11 名患者还在 48 小时内进行了后续 MRI。MRI 采集包括 DWI、SWI、假连续 ASL（pCASL）、FLAIR 和非对比血管造影序列。开发了一种框架，用于增强突出的低信号静脉征象，然后自动分割 SWI 半影区 ROI。计算表观弥散系数（ADC）图和脑血流（CBF）图。从 ADC 图分割梗塞核心 ROI，从 CBF 图分割 ASL 半影区 ROI 半自动。计算梗塞核心体积、SWI 半影区体积（SPV）和 pCASL 半影区体积，并计算不匹配比 和 。SWI 半影区 ROI 和 ASL 半影区 ROI 之间的 Dice 系数为 0.96±0.07。 与 相关性良好（r=0.90，p<0.05），验证了使用 SWI-DWI 不匹配比准确评估半影区的假设。此外，观察到高 SPV 与 MR 血管造影中血管闭塞之间存在显著相关性。随访数据显示，治疗后半影区组织（通过所提出的框架预测的位置和体积）得以挽救。此外，功能结果分析显示，93.3%的患者 > 1 受益于血管再通治疗。总体而言，使用 SWI-DWI 不匹配比自动定量评估半影区与 ASL PWI-DWI 不匹配比等效。该方法提供了一种替代半影区评估所需灌注序列的方法，对于没有灌注序列的方案可以减少 17%的扫描时间。
