Wang Kexin, Ju Licheng, Qiao Guanda, Liang Yajie, Wu Yihan, Chu Chengyan, Rogers Joshua, Li Yuguo, Cao Suyi, Dawson Valina L, Dawson Ted M, Walczak Piotr, Xu Jiadi
F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA; Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA.
F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, USA; Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Neuroimage. 2025 Jan;305:120993. doi: 10.1016/j.neuroimage.2024.120993. Epub 2024 Dec 31.
This study aims to investigate the variations in guanidino (Guan), amine and amide chemical exchange saturation transfer (CEST) contrasts in ischemic stroke using permanent middle cerebral artery occlusion (pMCAO) and transient MCAO (tMCAO) models at high (9.4T) and clinical (3T) MRI fields. CEST contrasts were extracted using the Polynomial and Lorentzian Line-shape Fitting (PLOF) method. Both pMCAO and tMCAO models were utilized to examine the B-dependence patterns and pH sensitivity of the different CEST contrasts in ischemic lesions compared to contralateral region. At 9.4T, GuanCEST showed the highest signal in the contralateral hemisphere for both stroke models, followed by lower signals from amideCEST and amineCEST, with maximum signals at B=1.2 μT for all CEST contrasts. In both stroke models, GuanCEST exhibited a significant decrease of 1.15-1.5 % in stroke lesions compared to the contralateral hemisphere (ΔGuanCEST) at an optimal B range of 1.2-1.6 μT at 9.4T. This represents more than double the pH sensitivity compared to amideCEST, which showed a reduction of 0.5-0.62 % under the same B conditions. In the tMCAO model, amineCEST increased by 3.85 % in the stroke lesion compared to the contralateral hemisphere at an optima B range of 1.6-2.5 μT. In contrast, for the pMCAO model, amineCEST increased by 0.87-1.0 % in the stroke lesion. At lower B values (<0.8 μT at 9.4T and <0.4 μT at 3T), the GuanCEST changes in the stroke lesion were dominated by creatine concentration changes, which increased in the pMCAO and remained stable in the tMCAO. While GuanCEST and amineCEST are highly sensitive for delineating stroke lesions, amideCEST is more suitable for precise pH mapping as it is not influenced by metabolite changes within the stroke lesion. Additionally, at low B values, amideCEST and GuanCEST can be used to map protein and creatine concentrations separately, since they are independent of pH changes at these lower B values. Lastly, amineCEST serves as a highly sensitive MRI contrast for detecting reperfusion damage at high MRI fields.
本研究旨在利用永久性大脑中动脉闭塞（pMCAO）和短暂性大脑中动脉闭塞（tMCAO）模型，在高场强（9.4T）和临床场强（3T）的磁共振成像（MRI）条件下，研究缺血性卒中中胍基（Guan）、胺和酰胺化学交换饱和转移（CEST）对比的变化。使用多项式和洛伦兹线形拟合（PLOF）方法提取CEST对比。利用pMCAO和tMCAO模型，研究缺血性病变与对侧区域相比，不同CEST对比的磁场依赖性模式和pH敏感性。在9.4T时，两种卒中模型中胍基CEST在对侧半球的信号最高，其次是酰胺CEST和胺CEST的较低信号，所有CEST对比在B = 1.2 μT时信号最强。在两种卒中模型中，在9.4T的最佳B范围1.2 - 1.6 μT下，与对侧半球相比，卒中病变中的胍基CEST显著降低1.15 - 1.5%（Δ胍基CEST）。这代表其pH敏感性是酰胺CEST的两倍多，在相同B条件下，酰胺CEST降低0.5 - 0.62%。在tMCAO模型中，在最佳B范围1.6 - 2.5 μT下，与对侧半球相比，卒中病变中的胺CEST增加3.85%。相比之下，对于pMCAO模型，卒中病变中的胺CEST增加0.87 - 1.0%。在较低的B值（9.4T时<0.8 μT，3T时<0.4 μT）下，卒中病变中胍基CEST的变化主要由肌酸浓度变化主导，在pMCAO中肌酸浓度增加，在tMCAO中保持稳定。虽然胍基CEST和胺CEST对描绘卒中病变高度敏感，但酰胺CEST更适合精确的pH映射，因为它不受卒中病变内代谢物变化的影响。此外，在低B值下，酰胺CEST和胍基CEST可分别用于映射蛋白质和肌酸浓度，因为它们在这些较低B值下与pH变化无关。最后，胺CEST是高场强MRI检测再灌注损伤的高灵敏度对比剂。
