Table 1. CT/MR Imaging characteristics of “target signs” in various conditions.

Types of target signs	Conditions	Centre	Periphery	Pathology correlate
CT contrast: two zone target	Tuberculoma (22)	Hypodense	Enhancing border	Centre: caseation Periphery: histiocytes + leaky inflamed vessels
	Metastases (23,24)	Hypodense	Enhancing border due to leaky blood vessels	Centre: inspissated mucin Periphery: leaky vessels
MRI T2WI: two zone target	Tuberculoma (25,26)	Hypo intense	Hyper intense	Centre: caseation Periphery: histiocytes + leaky inflamed vessels
	Toxoplasmosis (7)	Hyper intense	Hypo intense	Centre: fibrin + edema rich necrosis Periphery: closely packed histiocytes
MRI T1WI (post contrast): two zone target	Toxoplasmosis (27)	Iso/hypo intense	Ring enhancement	Not known
MRI T1WI (non enhanced): two zone target	Toxoplasmosis (28)	Hypo intense	Iso intense	Not known
MRI T1WI (post contrast): 3 zone target (eccentric/central target sign)	Toxoplasmosis (17)	Enhancing central/eccentric core	Intermediate: hypo intense Outer most: enhancing hyper intense	Organizing abscess stage Enhancing core: inflamed vessels in sulcus running through centre of lesion Intermediate hypo intensity: compact necrosis Enhancing periphery: inflammation, endarteritis (6)
MRI T2WI/FLAIR: 3 zone target (Concentric T2 target sign) Contrast pattern: not known	Toxoplasmosis (7)	Hypo intense	Intermediate: hyper intense Outer: iso Outer most: hypo intense	Central hypo intensities: hemorrhage Intermediate hyper intensities: fibrin rich necrosis Outer iso – compact necrosis Outermost hypo intensity – edema (present report)
MRI T2WI/FLAIR: 3 zone target (T2 target sign) T1 and Contrast: lamellar rings	Balo's concentric sclerosis (18)	Hyper intense	Alternating hypo intense	Alternate histiocyte rich foci of demyelination and remyelination