Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
Magn Reson Med. 2024 Feb;91(2):615-629. doi: 10.1002/mrm.29896. Epub 2023 Oct 23.
A new nuclear Overhauser enhancement (NOE)-mediated saturation transfer signal at around -1.6 ppm, termed NOE(-1.6), has been reported at high fields of 7T and 9.4T previously. This study aims to validate the presence of this signal at a relatively low field of 4.7T and evaluate its variations in different brain regions and tumors.
Rats were injected with monocrystalline iron oxide nanoparticles to reduce the NOE(-1.6) signal. CEST signals were measured using different saturation powers before and after injection to assess the presence of this signal. Multiple-pool Lorentzian fits, with/without inclusion of the NOE(-1.6) pool, were performed on CEST Z-spectra obtained from healthy rat brains and rats with 9L tumors. These fits aimed to further validate the presence of the NOE(-1.6) signal and quantify its amplitude.
The NOE(-1.6) signal exhibited a dramatic change following the injection of monocrystalline iron oxide nanoparticles, confirming its presence at 4.7T. The NOE(-1.6) signal reached its peak at a saturation power of ∼0.75 μT, indicating an optimized power level. The multiple-pool Lorentzian fit without the NOE(-1.6) pool showed higher residuals around -1.6 ppm compared to the fit with this pool, further supporting the presence of this signal. The NOE(-1.6) signal did not exhibit significant variation in the corpus callosum and caudate putamen regions, but it showed a significant decrease in tumors, which aligns with previous findings at 9.4T.
This study successfully demonstrated the presence of the NOE(-1.6) signal at 4.7T, which provides valuable insights into its potential applications at lower field strengths.
先前在 7T 和 9.4T 的高场中已经报道了一种新的核 Overhauser 增强（NOE）介导的饱和转移信号，约在-1.6ppm 处，称为 NOE(-1.6)。本研究旨在验证该信号在相对较低的 4.7T 场中存在，并评估其在不同脑区和肿瘤中的变化。
向大鼠注射单晶氧化铁纳米粒子以减少 NOE(-1.6)信号。使用注射前后不同的饱和功率测量 CEST 信号，以评估该信号的存在。对来自健康大鼠脑和 9L 肿瘤大鼠的 CEST Z 谱进行具有/不具有 NOE(-1.6)池的多池洛伦兹拟合，以进一步验证该信号的存在并量化其幅度。
注射单晶氧化铁纳米粒子后，NOE(-1.6)信号发生了显著变化，证实了其在 4.7T 处的存在。NOE(-1.6)信号在约 0.75μT 的饱和功率下达到峰值，表明存在最佳功率水平。与具有该池的拟合相比，不具有 NOE(-1.6)池的多池洛伦兹拟合在-1.6ppm 附近显示出更高的残差，进一步支持了该信号的存在。NOE(-1.6)信号在胼胝体和尾状核区域没有明显变化，但在肿瘤中明显减少，这与 9.4T 时的先前发现一致。
本研究成功地证明了 4.7T 处的 NOE(-1.6)信号的存在，为其在较低场强下的潜在应用提供了有价值的见解。
