Brain Tumor Imaging with Iopamidol CEST MRI: In Vivo Detection and Validation

Several diamagnetic CEST (chemical exchange saturation transfer) molecules have been proposed as a potential alternative to gadolinium-based contrast agents (CAs), with promising contrast efficiency properties. However, a direct comparison of CEST contrast agents in brain tumors, where gadolinium CAs are considered the gold standard for detecting primary masses, is still lacking. The aim of this study is to investigate the capability of Iopamidol, a CT contrast medium, to detect and delineate brain tumors in mice using the MRI-CEST technique compared with a conventional gadolinium-based contrast agent. Iopamidol provided enough contrast enhancement to detect and delineate brain tumors in both postinjection and contrast-enhanced images, comparable to Gadoteridol, in a glioblastoma murine model obtained upon stereotaxic injection of GL261 cells into C57BL/6 mice. Quantitative comparison between tumor and healthy tissue was assessed with contrast-to-noise ratio (CNR) and lesion-to-brain ratio (LBR) metrics. LBR values were 2.7-fold larger for Iopamidol than for Gadoteridol, although the CNR values were lower. The diagnostic accuracy of segmented tumor regions on both Iopamidol- and Gadoteridol-derived contrast images was calculated by the Tanimoto, DICE similarity, and volume similarity coefficients that indicated strong similarities between the contoured regions from Iopamidol and Gadoteridol contrast images. Moreover, moderate to excellent agreements were observed for intra- and interobserver variability. Overall, Iopamidol showed a capability similar to that of Gadoteridol to detect and contour the tumor area, with good diagnostic performance in terms of tumor border delineation in brain tumors.