Assessment of early radiation effects on the liver. Comparison of SPECT and MR.

Abstract

To evaluate the early effects of radiation on the liver using single photon emission CT (SPECT) with 99mTc-phytate combined with a pinhole collimator and MR imaging with superparamagnetic iron oxide (SPIO) and to compare 2 modalities regarding the assessment of the reticuloendothelial cell function. The right sides of the livers of 12 anesthetized rats were irradiated with X-rays (4000 cGy). On the 3rd and 4th days postirradiation, SPECT and MR imaging pre- and postcontrast were performed. On SPECT, the irradiated areas appeared as areas with reduced 99mTc-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 enhancement 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 nonirradiated areas, were visually less clear than those on the earlier postcontrast images. In the remaining 3 rats, no radiation damage was evident on MR images. SPECT with 99mTc-phytate and early postcontrast MR imaging with SPIO can show early radiation damage of the liver. The serial assessment of the postcontrast MR images provides functional information on the Kupffer cells.