ASSESSMENT OF EARLY RADIATION EFFECTS ON THE LIVER - COMPARISON OF SPECT AND MR

Purpose: To evaluate the early effects of radiation on the liver using single photon emission CT (SPECT) with Tc-99m-phytate combined with a pinhole collimator and MR imaging with superparamagnetic iron oxide ( SPIO) and to compare 2 modalities regarding the assessment of the reti culoendothelial cell function. Material and Methods: The right sides o f the livers of 12 anesthetized rats were irradiated with X-rays (4000 cGy). On the 3rd and 4th days postirradiation, SPECT and MR imaging p re- and postcontrast were performed. Results: On SPECT, the irradiated areas appeared as areas with reduced Tc-99m-phytate uptake in 9 rats. In the remaining 3 rats, irradiated lesions were not evident on SPECT . On the early postcontrast MR images, differential negative enhanceme nt of the irradiated and nonirradiated areas in the same 9 rats as on SPECT was apparent. However, on the later postcontrast images of 3 of these rats, the irradiated areas, which were brighter than the nonirra diated areas, were visually less clear than those on the earlier postc ontrast images. In the remaining 3 rats, nb radiation damage was evide nt on MR images. Conclusion: SPECT with Tc-99m-phytate and early postc ontrast MR imaging with SPIO can show early radiation damage of the li ver. The serial assessment of the postcontrast MR images provides func tional information on the Kupffer cells.