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首页> 外文期刊>Applied Magnetic Resonance >Chemical Exchange Saturation Transfer MRI Optimal Continuous Wave RF Irradiation Parameters for Glycogen (glycoCEST) Detection
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Chemical Exchange Saturation Transfer MRI Optimal Continuous Wave RF Irradiation Parameters for Glycogen (glycoCEST) Detection

机译：化学交换饱和度转移MRI最佳连续波RF照射参数糖原（Glycocest）检测

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摘要

Chemical exchange saturation transfer (CEST) enables detection of molecules such as glycogen, whose concentrations are too low to impact the signal intensity of standard MR imaging. Detection of these molecules is achieved by selectively saturating a molecule of interest and by measuring the reduction in water signal due to saturation transfer. CEST effects are dependent on parameters such as CEST agent concentration, pH, temperature, relaxation rate, magnetic field strength as well as on experimental parameters such as repetition time, RF irradiation amplitude, and the imaging readout scheme. Measurement of molecules with exchangeable protons that resonate very close to water, e.g., hydroxyl groups in glycogen, is challenging especially at lower magnetic field strengths, mainly due to the effect of direct water saturation. Therefore, optimal RF irradiation parameters that maximize the CEST signal and reduce the competing factors are important for better quantification of glycogen-weighted CEST effects. In this study, analytical solution of the Bloch-McConnell equations was used to find optimal continuous wave RF irradiation parameters for detection of glycogen. In vivo tests were performed on a human calf muscle at different saturation powers to validate the optimal saturation parameters determined via simulation. The selected parameters were applied in vitro to CEST measurements in a phantom with varying glycogen concentrations and also in vivo in a human calf muscle. Our results show the possibility of detecting glycogen using CEST MRI at 3 T. It is further shown that the glycoCEST signal can be maximized by optimizing the RF pulse irradiation parameters (duration and power) and that different glycogen concentrations can be identified when applying the optimized saturation pulse.
机译：化学交换饱和度转移（CEST）能够检测诸如糖原的分子，其浓度太低而无法冲击标准MR成像的信号强度。通过选择性地饱和感兴趣的分子并通过测量由于饱和转移引起的水信号的降低来实现这些分子的检测。 CEST效果依赖于CEST代理浓度，pH，温度，弛豫率，磁场强度以及实验参数等参数，如重复时间，RF照射幅度和成像读出方案。测量具有非常接近水的可交换质子的分子，例如糖原中的羟基，特别是在较低磁场强度下挑战，主要是由于直接水饱和的影响。因此，最大化CEST信号和降低竞争因子的最佳RF照射参数对于更好地定量糖原加权的CEST效应是重要的。在该研究中，使用Bloch-McConnell方程的分析解用于检测糖原的最佳连续波RF照射参数。在不同饱和功率下对人类小牛肌进行体内测试以验证通过模拟确定的最佳饱和度参数。将所选参数在体外应用于具有不同糖原浓度的体内的CETT测量，并且在人类小牛肌中的体内。我们的结果表明，在3℃下使用CEST MRI检测糖原的可能性。进一步示出了通过优化RF脉冲照射参数（持续时间和功率）并且可以在应用优化时识别不同的糖浓度来最大化Glycescist信号。饱和脉冲。

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