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目的评价降低时间分辨率对急性脑缺血疾病CT灌注结果精确性的影响。资料与方法对24例有急性脑缺血症状患者的头颅CT灌注成像资料进行回顾分析。获得的灌注成像资料分别以1帧/0.5 s、1帧/1.0 s、1帧/1.5 s、1帧/2.0 s、1帧/2.5 s、1帧/3.0 s、1帧/4.0 s、1帧/5.0 s及1帧/6.0 s的时间分辨率选取图像数据进行后处理。比较各自的时间密度曲线(TDC)、灌注伪彩功能图质量,对灌注参数值进行Friedman test、Kendall’s W test和Wilcoxon test统计学分析。结果随时间分辨率下降,TDC的形状变得陡直、不圆滑。各灌注参数图像质量视觉评分逐渐下降,以脑血流量(CBF)和平均通过时间(MTT)图更明显。对24例按不同时间分辨率分组的脑缺血患者灌注参数进行检验:(1)以所有感兴趣区为研究对象:时间分辨率下降至1帧/1.0 s,即已对CBF和MTT绝对值产生了显著影响,而下降到1帧/5.0 s时才对脑血容量(CBV)绝对值有显著影响。(2)以健侧大脑半球为研究对象:时间分辨率下降至1帧/1.0 s,即已对CBF、MTT绝对值产生了显著影响。时间分辨率的下降对CBV绝对值无显著影响。(3)以缺血侧大脑半球为研究对象:时间分辨率下降至1帧/1.0 s时,即已对CBF绝对值产生了显著影响,而下降到1帧/5.0 s时才对CBV绝对值有显著影响,对MTT绝对值无显著影响。(4)以缺血侧/健侧大脑半球灌注参数值的比值为研究对象:时间分辨率降至1帧/5.0 s,对MTT的相对值产生显著影响。时间分辨率的下降对CBV和CBF相对值的测量不会产生显著影响。结论时间分辨率的降低会影响各灌注参数值的准确测量,但对灌注参数相对值的影响比对灌注参数绝对值的影响要小,时间分辨率可以降低至1帧/4.0 s。
Objective To evaluate the effect of decreasing temporal resolution on the accuracy of CT perfusion in acute cerebral ischemic disease. Materials and Methods The head CT perfusion imaging data of 24 patients with acute cerebral ischemia were retrospectively analyzed. The obtained perfusion imaging data were recorded at 1 frame / 0.5 s, 1 frame / 1.0 s, 1 frame / 1.5 s, 1 frame / 2.0 s, 1 frame / 2.5 s, 1 frame / 3.0 s, 1 frame / 4.0 s, 1 Frame / 5.0 s and 1 frame / 6.0 s time resolution select the image data for post-processing. The time-density curve (TDC), the quality of perfusion pseudo-color chart were compared. The perfusion parameters were analyzed by Friedman test, Kendall’s W test and Wilcoxon test. As the result decreases with time resolution, the shape of TDC becomes steep and not smooth. The visual quality score of each perfusion parameter gradually decreased, which was more obvious with CBF and MTT. The perfusion parameters of 24 patients with cerebral ischemia grouped by different time resolution were tested: (1) All the regions of interest were studied: the temporal resolution decreased to 1 frame / 1.0 s, that is, the absolute values of CBF and MTT Had a significant impact, and dropped to 1 /5.0 s only when the absolute value of cerebral blood volume (CBV) had a significant impact. (2) To the contralateral hemisphere as the research object: the time resolution dropped to 1 frame /1.0 s, that has had a significant impact on CBF, MTT absolute value. The decrease of temporal resolution had no significant effect on the absolute value of CBV. (3) To the ischemic hemisphere as the object of study: When the time resolution dropped to 1 frame /1.0 s, it had a significant impact on the CBF absolute value, and dropped to 1 frame /5.0 s when the CBV absolute value Have a significant effect, no significant effect on the absolute value of MTT. (4) To the ratio of ischemic / contralateral hemisphere perfusion parameters as the research object: the time resolution dropped to 1 /5.0 s, the relative value of MTT had a significant impact. The decrease in temporal resolution does not have a significant effect on the relative CBV and CBF measurements. Conclusion The decrease of temporal resolution will affect the accurate measurement of perfusion parameters, but the influence on the relative perfusion parameters is smaller than the absolute perfusion parameters, and the temporal resolution can be reduced to 1 frame / 4.0 s.