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.