Factors affecting the chemical exchange saturation transfer of Creatine as assessed by 11.7 T MRI
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Chemical exchange saturation transfer (CEST) is a new contrast enhancement approach for imaging exogenous or endogenous substances such as creatine (Cr), amide protons, and glutamate in the human body. An increase in field strength is beneficial for CEST imaging because of the increased chemical shift and longer longitudinal relaxation time (T1). In high-field magnetic resonance imaging (MRI), establishing and evaluating the CEST effect is important for optimizing the magnetization transfer (MT) saturation radio frequency (RF) pulses. In this study, the CEST effect on Cr was evaluated at different concentrations in pH phantoms by appropriately selecting MT saturation RF pulses using 11.7 T MRI. The results showed that the CEST efficiency increased gradually with increasing applied saturation RF pulse power and that it was affected by the number of saturation RF pulses and their bandwidths. However, spillover effects were observed with higher saturation RF pulse powers. In conclusion, we successfully performed in vitro Cr CEST imaging under optimized conditions of MT saturation RF pulses.
KeywordsChemical exchange saturation transfer Creatine Magnetization transfer Spillover effect
Chemical exchange saturation transfer
Magnetic resonance imaging
Magnetic resonance spectroscopy
Magnetization transfer ratio
Rapid acquisition with relaxation enhancement
Longitudinal relaxation time
The authors would like to thank Mr. Junpei Ueda, Mr. Hisato Sasahara and Mr. Isamu Yabata (Graduate School of Medicine, Osaka University, Japan) for technical assistance. This work was partly supported by Grants-in-Aid for Scientific Research (Kakenhi, Nos. 24791299 and 24300167) by the Japan Society for the Promotion of Science (JSPS).
Conflict of interest
The authors declare that they have no conflicts of interest.