Assessment of Early Radiation Effects on the Liver

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. Material and Methods: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.Results: On SPECT, the irradiated areas appeared as areas with reduced 99mT~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.Conclusion: 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.Kupffer cell function has been investigated in radioisotope (RI) studies using 99"Tc-phytate, 9 9 m T~-~~1fur colloids and 19*Au (4, 7,. 13-15, 24). Irradiation of the liver was found to damage the Kupffer cells, hepatocytes and hepatic vascular structures (2,6,8,11,16) and the extent of these abnormalities depended on radiation dose, time after irradiation, and number of irradiation fractions (2,6,8,11,13,16). Late effects of liver irradiation have also been demonstrated by CT, MR imaging and ultrasonography (12,23,25).

Persistent T2*-hypointensity of the liver parenchyma after irradiation to the SPIO-accumulated liver: An imaging marker for responses to radiotherapy in hepatic malignancies

“…There is an emerging need to explore this technique especially in stereotactic body radiotherapy (SBRT) for liver malignancies because liver motion due to respiration and cardiac pulsation may produce mis‐registration between the target volumes and actual irradiated areas . A clear and simultaneous visualization of the irradiated liver parenchyma and cancer lesions remains challenging with currently available imaging techniques, including contrast‐enhanced computed tomography (CT) and MR imaging . Radiation‐induced changes in liver tissues hinder this visualization, particularly in acute and subacute phases after irradiation.…”