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Original Articles
Proton exchange rate quantification-based lesion detection in ischemic stroke using chemical exchange saturation transfer imaging
ZHAO Yingcheng  WANG Xiaoli  HE Xiaowei 

Cite this article as: Zhao YC, Wang XL, He XW. Proton exchange rate quantification-based lesion detection in ischemic stroke using chemical exchange saturation transfer imaging[J]. Chin J Magn Reson Imaging, 2022, 13(10): 157-163. DOI:10.12015/issn.1674-8034.2022.10.024.

[Abstract] 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 2 μT to collect CEST images three times. In terms of post-processing, the linear relationship between the saturation pulse amplitude ω1, the exchange rate kex and the CEST signal was established based on the Bloch-McConnell equation, so as to pass the CEST under different B1. 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 kex 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.
[Keywords] ischemic stroke;magnetic resonance imaging;chemical exchange saturation transfer;exchange rate;amide proton transfer;lesion detection

ZHAO Yingcheng1, 2   WANG Xiaoli3   HE Xiaowei1, 2*  

1 School of Information Sciences and Technology, Northwest University, Xi'an 710127, China

2 Xi'an Key Lab of Radiomics and Intelligent Perception, Northwest University, Xi'an 710127, China

3 Department of Medical Imaging, Weifang Medical University, Weifang 261053, China

He XW, E-mail:

Conflicts of interest   None.

Received  2022-05-12
Accepted  2022-09-22
DOI: 10.12015/issn.1674-8034.2022.10.024
Cite this article as: Zhao YC, Wang XL, He XW. Proton exchange rate quantification-based lesion detection in ischemic stroke using chemical exchange saturation transfer imaging[J]. Chin J Magn Reson Imaging, 2022, 13(10): 157-163.DOI:10.12015/issn.1674-8034.2022.10.024

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