transient hepatic intensity differences (THID)
Transient hepatic intensity differences (THIDs) are a phenomenon observed on MRI imaging of the liver. They are considered a direct equivalent to transient hepatic attenuation differences (THADs) noted on CT. They may be focal or nonfocal.
A focal THID lesion can arise from four pathological mechanisms
- directly by a siphoning effect (lobar multisegmental shape)
- indirectly by means of portal hypoperfusion (sectorial shape) due to portal branch compression or infiltration
- by thrombosis resulting in a portal branch blockade
- by flow diversion caused by an arterioportal shunt
These can be sectorial, polymorphous or diffuse and can arise from a variety of etiologies.