Double target sign (hepatic abscess)

The double target sign is a characteristic imaging feature of liver abscess on contrast enhanced CT scans, in which a central, fluid-filled low attenuation lesion is surrounded by a high attenuation inner rim and a low attenuation outer ring .

The inner ring (abscess membrane) demonstrates early contrast enhancement which persists on delayed images, in contrast to the outer rim (edema of the liver parenchyma) which only enhances on delayed phase . In other words, there is a rim-enhancing fluid collection surrounded by hypoenhancing edematous parenchyma.