Department of Neurosurgery, 50206Hirosaki Stroke and Rehabilitation Center, Japan.
Neuroradiol J. 2021 Aug;34(4):341-347. doi: 10.1177/1971400921998981. Epub 2021 Mar 3.
Non-infarcted acute cerebral ischaemic areas appear hypo-attenuated on non-contrast narrow-window computed tomography images. We aimed to determine the mechanism underlying minute computed tomography hypo-attenuation and visualise these attenuation changes on non-contrast computed tomography images.
The cerebral parenchyma was defined by pixels with attenuation of 20-50 Hounsfield units. We calculated the mean cerebral parenchymal attenuation in non-contrast computed tomography images. We analysed the correlation of complete blood counts with corresponding mean cerebral parenchymal attenuation values using linear regression analysis. Moreover, we developed an image processing method that involved pixel colorisation based on the noise-reduced attenuation value for minute cerebral parenchymal attenuation visualisation.
Haemoglobin, haematocrit and red blood cell counts positively correlated with mean cerebral parenchymal attenuation values. The cerebral haematocrit is correlated with the blood haematocrit; therefore, cerebral parenchymal attenuation correlated linearly with cerebral haemoglobin concentration. Haemoglobin contents in a pixel partially determine the X-ray absorption dose and attenuation value. Pixel haemoglobin contents are determined by the cerebral volume of blood in a pixel. Image processed computed tomography images reflected cerebral volume of blood and showed the same alterations with regional cerebral blood volume maps of perfusion computed tomography.
Cerebral parenchymal attenuation correlated with cerebral haemoglobin concentration and cerebral volume of blood. Infarcted cerebral parenchyma shows about 5 Hounsfield units gray matter attenuation decrease. Attenuation decrease by less than 5 Hounsfield units means decreased cerebral volume of blood, indicating a reversible functional change. One cannot recognise minute hypo-attenuation (<5 Hounsfield units) in routine computed tomography images. However, it can be visualised through an image processing method on non-contrast computed tomography images. It may detect pre-infarction cerebral volume of blood and regional cerebral blood volume alterations.
在非增强窄窗计算机断层扫描图像上，非梗死性急性脑缺血区域呈低衰减。本研究旨在确定微小计算机断层扫描衰减的机制，并在非增强计算机断层扫描图像上观察这些衰减变化。
脑实质由衰减值为 20-50 亨氏单位的像素定义。我们计算了非增强计算机断层扫描图像中的平均脑实质衰减值。我们使用线性回归分析来分析全血细胞计数与相应平均脑实质衰减值的相关性。此外，我们开发了一种图像处理方法，该方法涉及基于噪声降低衰减值的像素着色，以实现微小脑实质衰减的可视化。
血红蛋白、红细胞压积和红细胞计数与平均脑实质衰减值呈正相关。脑红细胞压积与血液红细胞压积相关；因此，脑实质衰减与脑血红蛋白浓度呈线性相关。像素中的血红蛋白含量部分决定了 X 射线吸收剂量和衰减值。像素中的血红蛋白含量取决于像素中脑内的血量。经图像处理的计算机断层扫描图像反映了脑内血量，并与灌注计算机断层扫描的局部脑血容量图显示出相同的变化。
脑实质衰减与脑血红蛋白浓度和脑内血量相关。梗死性脑实质的灰质衰减约为 5 亨氏单位。衰减值降低小于 5 亨氏单位意味着脑内血量减少，表明存在可逆转的功能变化。在常规计算机断层扫描图像中无法识别微小的低衰减（<5 亨氏单位）。但是，可以通过非增强计算机断层扫描图像上的图像处理方法进行观察。它可能可以检测到脑梗死前的脑内血量和局部脑血容量的变化。
