F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA.
Magn Reson Med. 2023 Jan;89(1):177-191. doi: 10.1002/mrm.29440. Epub 2022 Sep 5.
To extract guanidinium (Guan) and amide CEST on the human brain at 3 T MRI with the high spectral resolution (HSR) CEST combined with the polynomial Lorentzian line-shape fitting (PLOF).
Continuous wave (cw) turbo spin-echo (TSE) CEST was implemented to obtain the optimum saturation parameters. Both Guan and amide CEST peaks were extracted and quantified using the PLOF method. The NMR spectra on the egg white phantoms were acquired to reveal the fitting range and the contributions to the amide and GuanCEST. Two types of CEST approaches, including cw gradient- and spin-echo (cwGRASE) and steady state EPI (ssEPI), were implemented to acquire multi-slice HSR-CEST.
GuanCEST can be extracted with the PLOF method at 3 T, and the optimum was determined for GuanCEST in white matter (WM) and 1.0 μT in gray matter (GM). The optimum B = 0.8-1 μT was found for amideCEST. AmideCEST is lower in both WM and GM collected with ssEPI compared to those by cwGRASE (ssEPI = [1.27-1.63]%; cwGRASE = [2.19-2.25]%). The coefficients of variation (COV) of the amide and Guan CEST in both WM and GM for ssEPI (COV: 28.6-33.4%) are significantly higher than those of cwGRASE (COV: 8.6-18.8%). Completely different WM/GM contrasts for Guan and amide CEST were observed between ssEPI and cwGRASE. The amideCEST was found to have originated from the unstructured amide protons as suggested by the NMR spectrum of the unfolded proteins in egg white.
Guan and amide CEST mapping can be achieved by the HSR-CEST at 3 T combing with the PLOF method.
利用高光谱分辨率（HSR）CEST 结合多项式洛伦兹线拟合（PLOF），在 3T MRI 上从人脑提取胍基（Guan）和酰胺 CEST。
采用连续波（cw）涡轮自旋回波（TSE）CEST 获得最佳饱和参数。使用 PLOF 方法提取和定量分析 Guan 和酰胺 CEST 峰。在蛋清模型上采集 NMR 谱，以揭示拟合范围和对酰胺和 GuanCEST 的贡献。采用连续波梯度和自旋回波（cwGRASE）和稳态 EPI（ssEPI）两种 CEST 方法采集多切片 HSR-CEST。
可以使用 PLOF 方法在 3T 下提取 GuanCEST，并确定白质（WM）中的 GuanCEST 最佳值为 1.0μT，灰质（GM）中的最佳值为 1.0μT。酰胺CEST 的最佳 B 为 0.8-1μT。与 cwGRASE 相比，ssEPI 采集的 WM 和 GM 中的酰胺 CEST 均较低（ssEPI = [1.27-1.63]％；cwGRASE = [2.19-2.25]％）。ssEPI 中 WM 和 GM 中酰胺和 Guan CEST 的变异系数（COV）（COV：28.6-33.4％）明显高于 cwGRASE（COV：8.6-18.8％）。ssEPI 和 cwGRASE 之间观察到 Guan 和酰胺 CEST 在 WM 和 GM 之间具有完全不同的 WM/GM 对比。根据蛋清中未折叠蛋白的 NMR 谱，发现酰胺 CEST 源自无规酰胺质子。
结合 PLOF 方法，在 3T 上进行 HSR-CEST 可以实现 Guan 和酰胺 CEST 映射。
