Department of Medical Biophysics, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada.
Imaging Research Laboratories, Robarts Research Institute, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada.
J Neurointerv Surg. 2019 Nov;11(11):1155-1161. doi: 10.1136/neurintsurg-2019-014802. Epub 2019 May 14.
The efficacy of acute ischemic stroke treatment is affected by thrombus composition and age, yet no diagnostic method capable of quantitative thrombus characterization currently exists. This in vitro study evaluates the use of R , quantitative susceptibility mapping (QSM), and proton density fat fraction (FF) maps derived from a single gradient echo (GRE) MRI acquisition for characterizing clot of various hematocrit, as well as added calcified and lipidic components, throughout aging.
Two thrombus phantoms containing porcine clots (10-60% hematocrit, one with added calcium or lard) were scanned serially throughout 6 days of aging. Three-dimensional multi-echo GRE imaging was used to generate R , QSM, and FF maps, from which mean values for all clots at every time point were obtained. Receiver operating characteristic analysis was used to derive thresholds differentiating acute from chronic clot, and measured R and QSM were tested for their ability to estimate clot hematocrit.
R and QSM varied minimally over the first 6 hours of aging (acute), and QSM was found to linearly relate to clot hematocrit. Beyond 6 hours (chronic), R and QSM increased considerably over time and hematocrit could be estimated from the R /QSM ratio. R and QSM thresholds of 22 s and 0.165 ppm differentiated acute from chronic clots with a sensitivity/specificity of 100%/100% and 85%/92%, respectively. QSM and FF maps definitively distinguished calcium and lipid, respectively, from clots of any hematocrit and age.
R , QSM, and FF from a single multi-echo GRE scan discriminated hematocrit and age, and distinguished calcification and lipid withinin vitro clot.
急性缺血性脑卒中治疗的效果受到血栓组成和年龄的影响，但目前还没有能够定量描述血栓特性的诊断方法。本体外研究评估了使用 R 、定量磁化率映射（QSM）和从单次梯度回波（GRE）MRI 采集得出的质子密度脂肪分数（FF）图来描述不同血球比容的血栓特性，以及随着年龄的增长而增加的钙化和脂质成分。
两个包含猪血栓的血栓模型（血球比容 10-60%，其中一个添加了钙或猪油）在 6 天的老化过程中进行了连续扫描。使用三维多回波 GRE 成像生成 R 、QSM 和 FF 图，从中获得每个时间点所有血栓的平均值。采用受试者工作特征分析得出区分急性和慢性血栓的阈值，并测试测量的 R 和 QSM 估算血栓血球比容的能力。
在最初的 6 小时（急性）老化过程中，R 和 QSM 变化很小，并且 QSM 与血栓血球比容呈线性相关。超过 6 小时（慢性）后，R 和 QSM 随时间显著增加，并且可以从 R / QSM 比值估算血球比容。R 和 QSM 的阈值为 22s 和 0.165 ppm，可分别以 100%/100%和 85%/92%的灵敏度/特异性区分急性和慢性血栓。QSM 和 FF 图分别明确区分了任何血球比容和年龄的钙和脂质。
单次多回波 GRE 扫描的 R 、QSM 和 FF 可区分血球比容和年龄，并可区分体外血栓中的钙化和脂质。
