USPIO enhanced lymph node MRI using 3D multi‐echo GRE in a rabbit model

Ultrasmallsuperparamagnetic iron oxide (USPIO) has been suggested to be a negative MR contrast agent to detect metastatic lymph nodes. Previously reported studies have evaluated the diagnostic performance of USPIO‐enhanced MR lymph node imaging based on signal intensity. In this study, we investigate the specific performance of three different parametric approaches (normalized signal intensity, R 2 * and susceptibility) using 3D multi‐echo gradient echo to quantify the USPIO particles in lymph nodes. Nine rabbits with VX2 tumor implants were scanned before and after USPIO injection. From 3D multi‐echo GRE magnitude and phase data, we generated multi‐echo combined T 2 *‐weighted images, an R 2 * map, and a quantitative susceptibility map. Eighteen lymph nodes (nine reactive and nine metastatic) were evaluated and showed remarkable signal drops in the area of USPIO accumulation. On parametric analysis, the R 2 * difference before and after USPIO injection was significantly different ( p < 0.05) between reactive and metastatic lymph nodes; in contrast, the normalized signal intensity and susceptibility were not significantly different between the nodes. Our study showed the potential utility of USPIO‐enhanced MRI using R2* mapping from 3D multi‐echo GRE for the detection of lymph node metastasis and parametric analysis of lymph node status in a rabbit model.