期刊
MAGNETIC RESONANCE IN MEDICINE
卷 81, 期 1, 页码 645-652出版社
WILEY
DOI: 10.1002/mrm.27385
关键词
amide proton transfer; magnetization transfer; nuclear overhauser enhancement; chemical exchange saturation transfer; global ischemia; image downsampling expedited adaptive least-squares fitting
资金
- National Institutes of Health [R21NS085574, R01NS083654, P51OD011132]
- NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE [R01NS083654] Funding Source: NIH RePORTER
- OFFICE OF THE DIRECTOR, NATIONAL INSTITUTES OF HEALTH [P51OD011132] Funding Source: NIH RePORTER
Purpose: Chemical exchange saturation transfer (CEST) MRI has been used for quantitative assessment of dilute metabolites and/or pH in disorders such as acute stroke and tumor. However, routine asymmetry analysis (MTRasym) may be confounded by concomitant effects such as semisolid macromolecular magnetization transfer (MT) and nuclear Overhauser enhancement. Resolving multiple contributions is essential for elucidating the origins of in vivo CEST contrast. Methods: Here we used a newly proposed image downsampling expedited adaptive least-squares fitting on densely sampled Z-spectrum to quantify multipool contribution from water, nuclear Overhauser enhancement, MT, guanidinium, amine, and amide protons in adult male Wistar rats before and after global ischemia. Results: Our results revealed the major contributors to in vivo T-1-normalized MTRasym (3.5 ppm) contrast between white and gray matter (WM/GM) in normal brain (-1.96%/second) are pH-insensitive macromolecular MT (-0.89%/second) and nuclear Overhauser enhancement (-1.04%/second). Additionally, global ischemia resulted in significant changes of MTRasym, being -2.05%/second and -1.56%/second in WM and GM, which are dominated by changes in amide (-1.05%/second, -1.14%/second) and MT (-0.88%/second, -0.62%/second). Notably, the pH-sensitive amine and amide effects account for nearly 60% and 80% of the MTRasym changes seen in WM and GM, respectively, after global ischemia, indicating that MTRasym is predominantly pH-sensitive. Conclusion: Combined amide and amine effects dominated the MTRasym changes after global ischemia, indicating that MTRasym is predominantly pH-sensitive and suitable for detecting tissue acidosis following acute stroke.
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