MRI with superparamagnetic iron oxide: efficacy in the detection and characterization of focal hepatic lesions

Abstract

The purpose of this study was to evaluate the potential of superparamagnetic iron oxide particles (SPIO) as tissue specific contrast agent in magnetic resonance (MR) imaging in detection and characterization of focal hepatic lesions. We investigated 45 patients with focal hepatic lesions. T 1-weighted SE (TR 650/TE 15 ms) and T 2-weighted SE (TR 2015–2030/TE 45 and 90 ms) unenhanced images were obtained. After SPIO application we performed T 1-weighted images with and T 2-weighted images with and without fat suppression using the same image parameters. Liver signal intensity decreased by 74% (min 47%, max 83%) on T 2-weighted images after application of the contrast agent. Benign lesions (FNH, adenoma) showed an average signal drop of 40% (min 20%, max 47%) whereas malignant lesions showed no significant change of signal intensity on post-contrast images. The mean tumor-to-liver contrast-to-noise ratio (C/N) was improved in all post-contrast sequences irrespective of the lesion type. An additional increase of tumor-to-liver contrast by use of fat suppression technique could be established in the slightly T 2-weighted sequence (TE 45 ms). In metastases, divided in different size groups, we could determine a significant size relation of tumor-to-liver C/N. After SPIO application the number of detected lesions increased distinctly, especially small foci are more easily demonstrated. SPIO particles are a efficacious contrast agent for MR examinations of the liver. For tumor characterization T 1- and T 2-weighted pre- and post-contrast images are necessary. The T 1-weighted sequences are helpful to differentiate benign lesions such as cysts and hemangiomas from malignant lesions. Detection and differential diagnoses of hepatic lesions are improved by use of the SPIO-particles.