7T GluCEST in Discriminating Gliomas with Diverse Invasiveness Degrees and Its Association with Invasion Indices

This study aimed to evaluate and compare the effectiveness of glutamate chemical exchange saturation transfer (GluCEST) with that of proton MR spectroscopy (¹H-MRS) and other conventional magnetic resonance imaging in distinguishing gliomas of different invasiveness and exploring their correlation with the expression of Ki-67. Twenty-four adult male Sprague-Dawley rats were included and randomly divided into three subgroups of the gliomas: C6, 9L, and F98. Sequential GluCEST, ¹H-MRS, diffusion weighted imaging, and T2-weighted imaging scans were performed on the intracranial glioma-bearing rats using a 7.0T animal MRI scanner 10 days after tumor induction. Tumor tissue was analyzed histopathologically after the imaging protocol, with Ki-67 labeling index (LI), glial fibrillary acidic protein (GFAP), microvessel density (MVD) indicated by Cluster of Differentiation 34 (CD34), and conventional hematoxylin and eosin staining measured for each glioma model. The diagnostic efficacy of each imaging modality was calculated. Increased tumor GluCEST contrast was found to be associated with more aggressive gliomas. In comparison to various imaging techniques, GluCEST demonstrated the highest diagnostic efficacy. More importantly, GluCEST contrast demonstrated a strong positive correlation with the tumor volume, Ki-67 LI, and MVD. In conclusion, 7T GluCEST imaging enables noninvasive visualization of the glutamate microenvironment of gliomas, thereby offering a reliable and promising imaging approach for differentiating the invasiveness of gliomas.