The triple-phase CT image appearance of post-irradiated livers

Objective: To evaluate the sequential CT appearance of the liver after hepa tic irradiation and to investigate the correlation between CT findings and radiation-induced hepatic injury. Material and Methods: The triple-phase CT images of 18 patients with hepato cellular carcinomas (HCC) after hepatic irradiation were retrospectively re viewed (in total 41 CT studies). The high-dose region within the liver was defined as the area receiving more than 90% of the prescribed irradiation d ose. The mean radiation dose was 55.5 Gy. Density changes and patterns of e nhancement in the high-dose region were classified as three types: type I, constant low-density change in all phases; type II, low-density change in b oth pre-contrast and arterial phases, and iso-density change in the portal phase; type III, low- or iso-density change in the pre-contrast phase, low- or high-density change in the arterial phase, and persistent high-density change in the portal phase. The interval between completion of radiotherapy and the CT examinations ranged from 9 to 469 days, with a mean of 147 days . Results: Nine of the 41 CT studies presented with type I, 9 with type II, a nd 16 with type III CT findings. The mean interval between completion of ra diotherapy and the appearance of types I, II, and III CT findings were 74, 183, and 220 days, respectively. The interval was significantly shorter for type I findings than for type II and type III. The difference in interval was not significant between type II and type III. A type I finding with con stant low-density change in the high-dose region of the liver was the most common pattern of CT findings within the first 3 months after hepatic irrad iation. Either types II or III findings were frequently seen after 3 months . Conclusion: The sequential CT appearance and the density changes may indica te correlation with the pathogenesis of veno-occlusive disease.