Decrease of signal intensity of myometrium and cervical stroma after ultrasmall superparamagnetic iron oxide (USPIO) particles administration - An MR finding with potential benefits in T staging of uterine neoplasms

Objectives: Following the empiric observation of a significant decrease of signal intensity of both myometrium and cervical stroma on ultrasmall superparamagnetic iron oxide (USPIO)-enhanced images, the aim of our study was to evaluate whether USPIO-enhanced T2*-weighted gradient echo (GRE) images might provide any potential advantage on T-staging of uterine malignancies having surgery and histology as standard of reference. Materials and Methods: Seventeen female patients with known uterine malignancies underwent magnetic resonance (MR) imaging before and 24 hours after the intravenous administration of the USPIO agent. Imaging protocol included proton density-weighted turbo spin echo and T2*-weighted GRE sequences. Each patient underwent surgery within 14 days from the first MR examination, and histologic confirmation of tumor T-stage was obtained. Quantitative (calculation of signal-to-noise and contrast-to-noise ratios) and qualitative (visual assessment of T staging) analyses were performed on unenhanced and USPIO-enhanced images. Results: Quantitative analysis showed a significantly lower (P < 0.05) signal-to-noise ratio of myometrium and cervical stroma on USPIO-enhanced compared with unenhanced images. In 15 of 17 patients (88.2%), the contrast-to-noise ratio between tumor and myometrium and between tumor and cervical stroma was higher on USPIO-enhanced compared with unenhanced images (P < 0.001). Qualitative analysis demonstrated that the GRE T2* USPIO-enhanced MR offers a better definition of the depth of tumor infiltration rather than the unenhanced GRE T2* images. Conclusion: The decrease of signal intensity of myometrium and cervical stroma on T2*-weighted GRE images after the intravenous administration of USPIO should be considered a constant and physiologic finding that improves tumor conspicuity in the majority of the cases, allowing more accurate T-staging of neoplastic lesions.