Carlo Miglio | PubMed Health

PubMed2004

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.

Adult↗

PubMed2002

Oral contrast agents for magnetic resonance imaging of the bowel.

The development of fast imaging sequences, which provide the ability to acquire motion-free T1- and T2-weighted images of static fluids, has greatly increased the interest in magnetic resonance imaging of the small bowel. Luminal distension is a necessary prerequisite for small bowel imaging methods because collapsed bowel loops can hide even large lesions and may mimic wall thickening. Poor distension of normal bowel loops in basal conditions has led researchers to study different oral contrast media to optimally distend the bowel lumen. Several MR oral contrast agents with various signal properties are available. According to these signal properties, agents are classified as positive ("bright" lumen), negative ("dark" lumen), or biphasic ("bright" lumen on T1 and "dark" on T2, or conversely "dark" lumen on T2 and "bright" on T1). Positive contrast agents cause a reduction in T1 relaxation time; consequently, these agents act on T1-weighted images by increasing the signal intensity of the bowel lumen. Negative contrast agents are based on superparamagnetic particles and act by inducing local field inhomogeneities, which results in shortening of both T1 and T2 relaxation times. Using superparamagnetic contrast agents, T2-weighted effects are predominant. Biphasic contrast agents are substances that have different signal intensities on different sequences, depending on the concentration at which they are administered. The choice of a single agent presents advantages and disadvantages; thus, the radiologist should choose the appropriate contrast medium according to the clinical setting, MR experience, availability of the agent, and patient tolerance.

Administration, Oral↗