Target sign (tuberculosis)

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The target sign of tuberculosis refers to the bull's eye appearance of some parenchymal tuberculomas involving the brain (see: CNS tuberculosis) and solid abdominal organs (see: hepatic and splenic tuberculosis) on cross-sectional imaging.

Radiographic features

Ultrasound
  • hypoechoic nodules with more echogenic or calcified central areas (hepatic tuberculosis)
CT
  • central nidus of calcification surrounded by an area of low attenuation on plain CT
  • central enhancement surrounded by an area of low attenuation and/or ring of enhancement on contrast-enhanced CT
MRI
  • central enhancement accompanied by peripheral rim enhancement on post-contrast MRI