Vessels within zone may appear normal (no mass effect)
Usually low density on NECT and CECT
May have mixed hypervascular and hypovascular foci
• Region of radiation damage that is hypodense on portal venous phase may become hyperdense with prolonged enhancement on delayed phase
Due to ↓ vascular perfusion, ↓ hepatic venous drainage, and subsequent stasis of contrast medium
• MR, especially T1WI with in- and opposed-phase GRE, is best means of distinguishing RILD from steatosis
TOP DIFFERENTIAL DIAGNOSES
• Focal steatosis
• Hepatic infarction
PATHOLOGY
• Patients receiving single 1,200-rad dose of external beam radiation or a 4,000 to 5,500-rad fractionated dose over 6 weeks can develop RILD
• Hepatic arterial administration of yttrium-90 glass microspheres
Emit radiation to perfused hepatic area persisting for 64-hour half-life
CLINICAL ISSUES
• Complete clinical recovery typically seen within 60 days, but there may be permanent hepatocyte loss, fat deposition, fibrosis, and obliteration of central veins
(Left) Axial CECT shows a vertically oriented zone of low attenuation extending from the cranial to caudal aspect of the liver in a straight line , following external radiation therapy for lymphoma.
(Right) Axial CECT shows a straight line of demarcation of damaged liver in the left lobe due to external radiation therapy for esophageal carcinoma. Note the normal appearance of the left hepatic vein within the zone of radiation-induced liver disease (RILD).
(Left) Axial CECT shows decreased attenuation within the posterior segments of the liver, with a straight line of demarcation corresponding to the segments that had received yttrium-90 microsphere embolization for hepatocellular carcinoma (HCC). Note the normal appearance of the posterior right portal vein within the damaged liver.
(Right) CECT section from the same case shows viable satellite foci of HCC within the untreated anterior segments of liver .
TERMINOLOGY
Abbreviations
• Radiation-induced liver disease (RILD)
Definitions
• Syndrome characterized by development of anicteric ascites ∼ 2 weeks to 4 months after hepatic irradiation
• Form of venoocclusive disease due to fibrous obliteration of terminal hepatic venules → postsinusoidal obstruction
IMAGING
General Features
• Best diagnostic clue
Sharp line of demarcation between normal and abnormal parenchyma corresponds to radiation port or vascular distribution of yttrium-90 microspheres
CT Findings
• NECT
Sharply defined band of low attenuation corresponding to treatment port
– Probably due to hepatocellular necrosis, edema, and steatosis
If hepatic congestion is severe, patchy congestion simulating tumor nodules may be seen
In patients with diffuse hepatic steatosis, irradiated area may appear as region of increased attenuation
– May be due to loss of fat in irradiated hepatocytes or regional edema
Over time, sharp borders of irradiated zone become more irregular and indistinct (peripheral parenchyma regenerates)
– Eventually, irradiated area may become atrophic
• CECT
Enhancement pattern of irradiated liver may vary depending on preexisting hepatic pathology
Intense enhancement of irradiated parenchyma may be seen in acute phase injury
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, following external radiation therapy for lymphoma.
in the left lobe due to external radiation therapy for esophageal carcinoma. Note the normal appearance of the left hepatic vein 
within the zone of radiation-induced liver disease (RILD).
corresponding to the segments that had received yttrium-90 microsphere embolization for hepatocellular carcinoma (HCC). Note the normal appearance of the posterior right portal vein 
within the damaged liver.
.
Intense enhancement of irradiated parenchyma may be seen in acute phase injury
