Delayed hepatic signal recovery on ferucarbotran-enhanced magnetic resonance images in a rat model with regional liver irradiation

Abstract

To determine whether superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging could demonstrate signal recovery delay in irradiated areas of rat livers. We also investigated the relationship between MR imaging and histological findings. Twelve rats received 20μmol iron/kg of SPIO followed by X-irradiation to the right upper abdomen 4h later. Radiation doses were 0, 50 and 70Gy. Hepatic signals were assessed on unenhanced T 2 (*) -weighted images for up to 7days using a 9.4-Tesla scanner. The livers were excised on day 7 and examined histologically. Normalized relative signal intensity of 70Gy-irradiated right liver lobe (2.36±0.22) and 50Gy-irradiated right liver lobe (2.37±0.46) was significantly lower than that of the non-irradiated right liver lobe (4.04±0.28) on day 7, respectively (p<0.05). Pearson product-moment correlation coefficient between relative intensity of the liver and the number of hepatic iron deposits was -0.588 (p<0.01). Superparamagnetic iron oxide-enhanced MR imaging could demonstrate signal recovery delay in irradiated areas of rat livers. It seems that the signal recovery delay in irradiated areas was due to SPIO-derived iron deposition. Hepatic signal recovery could be a novel diagnostic marker for delineation of irradiated areas.