Objective: To characterize the computed tomographic (CT) findings of post-radiation livers and the interval changes in
patients with unresectable cholangiocarcinoma.

Material and Method: Thirteen patients with unresectable cholangiocarcinoma who received concurrent chemoradiation
with conformal radiotherapy technique (50 to 66 Gy, 2 Gy/fraction) were included in the present study. CT at pre-radiation
and sequential follow-up at 1, 3, 6, 9 and 12 months were retrospectively reviewed by two abdominal radiologists to identify
CT characteristics of post-radiation liver and the interval changes.

Results: CT at pre-radiation and sequential follow-up at 1, 3, 6, 9 and 12 months were available in 92.3%, 100%, 76.9%,
53.8%, 30.8% and 23.1%, respectively. Post-radiation livers showed sharply-delineated, hypodense radiation areas, which
were well related with the isodose line of 35 to 56 Gy (mean = 44.4 + 6.55 Gy). These radiation areas were mostly appreciated
on portal venous phase at 1-month follow-up study in 12 of 13 (92.3%) patients and these were gradually less defined in
subsequent studies. Progressive decrease size of radiation areas with persistent enhancement on delayed phase images were
recognized. Progression of hepatic cortical irregularity was seen in four (30.8%) patients, as well as pulmonary fibrosis of
lung bases.

Conclusion: Post-radiation liver in patients with unresectable cholangiocarcinoma showed a sharply-defined, hypodense
radiation area, which was mostly appreciated in 1-month follow-up CT and was gradually less defined in subsequent studies
with evidence of progressive atrophic change.

Keywords: Computed tomography CT, Conformal radiotherapy, Radiation-induced liver disease RILD