基于化学交换饱和转移成像中质子交换速率定量的缺血性脑卒中病灶检测研究  

Proton exchange rate quantification-based lesion detection in ischemic stroke using chemical exchange saturation transfer imaging

作　　者：赵映程 王晓莉[3] 贺小伟[1,2] ZHAO Yingcheng;WANG Xiaoli;HE Xiaowei(School of Information Sciences and Technology,Northwest University,Xi'an 710127,China;Xi'an Key Lab of Radiomics and Intelligent Perception,Northwest University,Xi'an 710127,China;Department of Medical Imaging,Weifang Medical University,Weifang 261053,China)

机构地区：[1]西北大学信息科学与技术学院,西安710127 [2]西北大学西安市影像组学与智能感知重点实验室,西安710127 [3]潍坊医学院医学影像学系,潍坊261053

出　　处：《磁共振成像》2022年第10期157-163,共7页Chinese Journal of Magnetic Resonance Imaging

基　　金：国家自然科学基金(编号:61971350)。

摘　　要：目的通过对化学交换饱和转移(chemical exchange saturation transfer,CEST)MRI进行质子交换速率(exchange rate,k_(ex))定量分析,评估该指标用于缺血性脑卒中病灶区域检测的价值。材料与方法采用栓线法制备大鼠大脑中动脉闭塞模型,在Bruker 7 T动物MR扫描仪上进行扫描,得到不同MRI模态的脑卒中大鼠成像,其中,设置B_(1)饱和脉冲强度分别为0.7、1、2μT来采集3次CEST影像。在图像后处理中,基于Bloch-McConnell方程建立饱和脉冲振幅(ω_(1))、k_(ex)和CEST信号之间的线性关系,从而通过不同B_(1)下的CEST信号进行k_(ex)定量,根据此方法对CEST影像进行逐像素计算以获得相应的k_(ex)成像。采用独立样本t检验法对检测出的病灶区域及正常组织的k_(ex)进行组间对比,以及使用对比噪声比(contrast-to-noise ratio,CNR)指标对k_(ex)成像和原始CEST成像进行量化对比。结果相对于对侧正常组织,k_(ex)成像在病灶区域呈现出明显的低信号;相较于横向弛豫加权成像(transverse relaxation-weighted,T2WI)和弥散加权成像(diffusion-weighted imaging,DWI),对于再灌注后短期内的情形,k_(ex)成像表现出更强的病灶区域对比度;通过k_(ex)成像检测出的病灶区域中的k_(ex)值相比其余正常组织差异具有统计学意义(P<0.01);在6组大鼠的对比实验中,对比原始CEST成像,k_(ex)成像均表现出了更高的CNR值。结论质子k_(ex)成像能够检测到缺血性卒中后组织的酸性病变,具有作为内源性定量成像生物标志物的潜质。Objective:To evaluate the value of chemical exchange saturation transfer(CEST)MRI proton exchange rate in the detection of focal area of ischemic stroke by quantitative analysis.Materials and Methods:The rat middle cerebral artery occlusion model was prepared by the suture method,and scanned on a Bruker 7 T animal MR scanner to obtain stroke rat images with different MRI modalities.The saturation pulse intensities were respectively 0.7,1,and 2μT to collect CEST images three times.In terms of post-processing,the linear relationship between the saturation pulse amplitudeω_(1),the exchange rate k_(ex) and the CEST signal was established based on the Bloch-McConnell equation,so as to pass the CEST under different B_(1).Signals were exchanged for rate quantification.According to this method,the CEST images were calculated pixel by pixel to obtain the corresponding exchange rate imaging.The independent sample t-test was used to compare the exchange rates of detected lesions and normal tissues between groups,and the contrast-to-noise ratio(CNR)was used to compare the exchange rates between groups.The CNR metric to quantify the contrast between exchange rate imaging and raw CEST imaging.Results:Relative to the contralateral normal tissue,exchange rate imaging showed markedly low signal in the lesion area.Compared with transverse relaxation-weighted imaging(T2W)and diffusion-weighted imaging(DWI),for the short term after reperfusion,exchange rate imaging showed stronger contrast in the lesion area.The k_(ex) value in the lesion area detected by exchange rate imaging was statistically significant compared with the rest of the normal tissues(P<0.01).With a total of 6 groups of rat comparison experiments,all the exchange rate images showed higher CNR values compared to the original CEST images.Conclusions:Proton exchange rate imaging can detect acidic lesions in tissues after ischemic stroke,and has potential as an endogenous quantitative imaging biomarker.

关 键 词：缺血性脑卒中 磁共振成像 化学交换饱和转移 交换速率 酰胺质子转移成像 病灶检测 

分 类 号：R445.2[医药卫生—影像医学与核医学] R743.3[医药卫生—诊断学]