Emory National Primate Research Center, Emory University, Atlanta, GA, United States of America; Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States of America.
Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States of America.
Magn Reson Imaging. 2023 Oct;102:229-234. doi: 10.1016/j.mri.2023.06.005. Epub 2023 Jun 14.
Chemical exchange saturated transfer (CEST) MRI has biomarker potential to assess tissue microenvironment in brain tumors. Multi-pool Lorentzian or spinlock models provides useful insights into the CEST contrast mechanism. However, T contribution to the complex overlapping effects of brain tumors is difficult under the non-equilibrium state. Therefore, this study evaluated T contributions on multi-pool parameters with quasi-steady-state (QUASS) algorithm reconstructed equilibrium data. MRI scans were performed in rat brain tumor models, including relaxation, diffusion, and CEST imaging. A pixel-wise seven-pool spinlock-model was employed to fit QUASS reconstructed CEST Z-spectra and evaluated the magnetization transfer (MT), amide, amine, guanidyl, and nuclear-overhauled effect (NOE) signals in tumor and normal tissues. In addition, T was estimated from the spinlock-model fitting and compared with measured T. We observed tumor had a statistically significant increase in the amide signal (p < 0.001) and decreases in the MT and NOE signals (p < 0.001). On the other hand, the differences in amine and guanidyl between the tumor and contralateral normal regions were not statistically significant. The differences between measured and estimated T values were 8% in the normal tissue and 4% in the tumor. Furthermore, the isolated MT signal strongly correlated with R (r = 0.96, P < 0.001). In summary, we successfully unraveled multi-factorial effects in the CEST signal using spinlock-model fitting and QUASS method and demonstrated the effect of T relaxation on MT and NOE.
化学交换饱和传递 (CEST) MRI 具有评估脑肿瘤组织微环境的生物标志物潜力。多池洛伦兹或自旋锁定模型为 CEST 对比机制提供了有用的见解。然而，在非平衡状态下，T 对脑肿瘤复杂重叠效应的贡献难以确定。因此，本研究使用准稳态 (QUASS) 算法重建平衡数据，评估多池参数中 T 的贡献。在大鼠脑肿瘤模型中进行了 MRI 扫描，包括弛豫、扩散和 CEST 成像。采用七池自旋锁定模型对 QUASS 重建的 CEST Z 谱进行拟合，并评估肿瘤和正常组织中的磁化转移 (MT)、酰胺、胺、胍基和核覆盖效应 (NOE) 信号。此外，还从自旋锁定模型拟合中估计 T 值，并与测量的 T 值进行比较。我们观察到肿瘤中的酰胺信号有统计学意义上的增加 (p < 0.001)，MT 和 NOE 信号有统计学意义上的降低 (p < 0.001)。另一方面，肿瘤与对侧正常区域之间的胺和胍基差异无统计学意义。正常组织中测量值与估计值之间的 T 值差异为 8%，肿瘤中为 4%。此外，孤立的 MT 信号与 R 高度相关 (r = 0.96，P < 0.001)。总之，我们使用自旋锁定模型拟合和 QUASS 方法成功揭示了 CEST 信号中的多因素效应，并证明了 T 弛豫对 MT 和 NOE 的影响。
