Invest Radiol. 2018 Apr;53(4):207-213. doi: 10.1097/RLI.0000000000000430.
Net water uptake per volume of brain tissue may be calculated by computed tomography (CT) density, and this imaging biomarker has recently been investigated as a predictor of lesion age in acute stroke. However, the hypothesis that measurements of CT density may be used to quantify net water uptake per volume of infarct lesion has not been validated by direct volumetric measurements so far. The purpose of this study was to (1) develop a theoretical relationship between CT density reduction and net water uptake per volume of ischemic lesions and (2) confirm this relationship by quantitative in vitro and in vivo CT image analysis using direct volumetric measurements.
We developed a theoretical rationale for a linear relationship between net water uptake per volume of ischemic lesions and CT attenuation. The derived relationship between water uptake and CT density was tested in vitro in a set of increasingly diluted iodine solutions with successive CT measurements. Furthermore, the consistency of this relationship was evaluated using human in vivo CT images in a retrospective multicentric cohort. In 50 edematous infarct lesions, net water uptake was determined by direct measurement of the volumetric difference between the ischemic and normal hemisphere and was correlated with net water uptake calculated by ischemic density measurements.
With regard to in vitro data, water uptake by density measurement was equivalent to direct volumetric measurement (r = 0.99, P < 0.0001; mean ± SD difference, -0.29% ± 0.39%, not different from 0, P < 0.0001). In the study cohort, the mean ± SD uptake of water within infarct measured by volumetry was 44.7 ± 26.8 mL and the mean percent water uptake per lesion volume was 22.7% ± 7.4%. This was equivalent to percent water uptake obtained from density measurements: 21.4% ± 6.4%. The mean difference between percent water uptake by direct volumetry and percent water uptake by CT density was -1.79% ± 3.40%, which was not significantly different from 0 (P < 0.0001).
Volume of water uptake in infarct lesions can be calculated quantitatively by relative CT density measurements. Voxel-wise imaging of water uptake depicts lesion pathophysiology and could serve as a quantitative imaging biomarker of acute infarct lesions.
通过计算机断层扫描（CT）密度可以计算出单位脑组织的净水分摄取量，最近该影像学标志物已被用于研究急性脑卒中时的病灶年龄预测。然而，目前尚未通过直接体积测量来验证 CT 密度测量是否可用于量化单位梗死病灶的净水分摄取量这一假说。本研究旨在：（1）建立单位缺血性病变净水分摄取量与 CT 衰减之间的理论关系；（2）通过使用直接体积测量的体外和体内 CT 图像定量分析来验证这种关系。
我们提出了一个理论依据，认为单位缺血性病变的净水分摄取量与 CT 衰减之间存在线性关系。在一系列浓度逐渐降低的碘溶液中进行了体外实验，连续进行 CT 测量，以验证水摄取与 CT 密度之间的关系。此外，还使用回顾性多中心队列的人体体内 CT 图像对该关系的一致性进行了评估。在 50 个水肿性梗死病灶中，通过测量缺血半球与正常半球之间的体积差异来确定净水分摄取量，并将其与通过缺血密度测量计算的净水分摄取量进行相关性分析。
就体外数据而言，通过密度测量的水摄取量等同于直接体积测量（r=0.99，P<0.0001；平均差异±标准差，-0.29%±0.39%，与 0 无差异，P<0.0001）。在研究队列中，通过体积测量法测量的梗死区内水的平均摄取量为 44.7±26.8mL，每个病灶体积的平均水分摄取百分比为 22.7%±7.4%。这与通过密度测量得出的水分摄取百分比相当：21.4%±6.4%。直接体积测量法与 CT 密度测量法测量的水分摄取百分比之间的平均差异为-1.79%±3.40%，与 0 无显著差异（P<0.0001）。
可以通过相对 CT 密度测量定量计算梗死病灶的水分摄取量。水摄取的体素成像可以描绘病灶的病理生理学特征，并且可以作为急性梗死病灶的定量影像学标志物。
