OBJECTIVETo study the pathological basis of radiological reaction types of radiation-induced liver disease on multiphasic CT scans.

METHODSThree pigs (tagged with A, B, and C) were subjected to single-dose radiation of 40, 40 and 30 Gy on the right or left lobe of the liver, respectively. At 42, 56, 133, and 168 days after irradiation, all pigs were examined with non-enhanced scan and contrast-enhanced scans at different time points after contrast injection. Hounsfield units (HU) were measured in each CT study to evaluate the density of irradiated and non-irradiated liver tissue to determine the reaction type. Liver tissues in the irradiation area obtained by needle biopsy with CT guidance were examined with electron microscopy, and specimens of the tissue corresponding to the region of interest on CT were obtained from necropsies for pathological examination.

RESULTSRadiologically, the 3 pig models presented with 3 reaction types on the multiphasic CT scans on days 133, 56, and 168 after radiation, respectively. Type 1 presented constant low-density change in all phases, the pathological basis of which was radiation hepatitis; type 2 showed pre-contrast phase isodense, arterial phase hyperdense, portal phase isodense and later phase hyperdense changes; type 3 was characterized by pre-contrast phase isodense, arterial phase hyperdense, portal phase hypodense and later phase hyperdense changes. The pathological basis of the last two radiological reaction types was radiation cirrhosis (postnecrotic cirrhosis).

CONCLUSIONSDifferent radiological reaction types of radiation liver injury on multiphase CT have different pathological basis, and multiphase contrast-enhanced CT may help distinguish the radiation reactions from tumor recurrence.