Early detection of radiation-induced liver injury in rat by superparamagnetic iron oxide-enhanced MR imaging

The detectability of early liver injury induced by irradiation was studied using magnetic resonance (MR) imaging enhanced with superparamagnetic iron oxide (SPIO), a tissue-specific contrast agent against the reticuloendothel ial system (RES), In rat, 3 days after focal irradiation (0-10 Gy), MR imag ing was performed and specimens were obtained to observe the phagocytic fun ction of RES. The irradiated portion of the liver was visualized with a cle ar demarcation from the nonirradiated part by SPIO-enhanced MR images as a decrease in negative enhancement reflecting the function of RES (P < 0.05), whereas this was impossible with nonenhanced MR images, Significant regres sion was observed as a dose-related change of the signal intensity in the i rradiated portion on SPIO-enhanced MR images (R = 0.867, P < 0.0001). SPIO- enhanced MR imaging was reliable for detecting the range and extent of live r injury a few days after low-dose irradiation, and it may be a useful proc edure for verifying the target area in clinical cases of radiation therapy. J. Magn, Reson. Imaging 1999:9:573-578, (C) 1999 Wiley-Liss, Inc.