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.

Abstract

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 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. 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. 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.