ct - ring enhancing lesion

IMAGE of the week

Dr. Prof. Mageshkumar Unit Devendra Patil

Syed Ilias , 34 / M Investigated outside for focal seizuresCT taken outside suggested a mass lesionPt was started on ATT.

Came with complains of Inability to use his left upper and lower limbsLeft Focal Seizures with generalization

MRI brain was taken.

T1w image :Hypointensity is seen in the right fronto parietal region T2w image :A lesion in the region of central fissure with central non-homogenous

hyperintensity with a hypointense rim with surrounding hyperintensity

T2 FLAIR :The same lesion maintains its hyperintensity and has a non

homogenous / nodular like lesion.Inner hyperintensity ; rim of hypointensity ; surrounding

hyperintensity.Post Gadolinium:The same rim shows enhancement but the centre is not

homogenously hypointense. It shows nodular hyperintensityThere are two other lesions seen:A ring enhancing lesion in post central gyrusA homogenous enhancing lesion in sup temporal gyrus

d/d for multiple ring enhancing lesions

T – TuberculomaN- Neurocysticerosis

M - Metastasis, MS A - Abscess (also cerebritis) G - Glioblastoma, Granuloma I - Infarct (esp. Basal ganglia) C - Contusion (rare) A - AIDS (Toxoplasmosis, etc.) L - Lymphoma (common in AIDS )

D - Demyelination (active) R - Resolving hematoma, Radiation change (necrosis)

SESSION GOALS:

TUBERCULOMANEUROCYSTICERCOSISTOXOPLASMOSISCEREBRAL ABSCESS

TUBERCULOMA

• It is seen from review of radiological literature that there is no characterstic appearance pathognomonic of TB granuloma and the diagnosis rests upon the use of history , clinical findings and response to treatment and bacteriological and histological examination.

• Usual mri findings:Central necrosis tends to a hyperintensity in T2

weighted images and peripheral hypointensity.However more solid lesions have a striking hypointense

in T2WI as a result of granulation tissue and compressed glial tissue in the central core

In some cases the lesion appears to have alternating layers of hyper and hypo intensities due to granulation tissue deposits

In almost all cases the lesion appears to be gray mater intensity in T1 WI.

On Gd enhancement ring or nodular lesions are seen

TUBERCULOMA

T1 w IMAGE T2 w IMAGE

NEUROCYSTICERCOSIS

Neurocysticercosis

• Different types of intracranial lesions seen viz., parenchymal , subarachnoid , intraventricular and spinal.

• CT is the best screening tool because :It detects calcification easilyIt is more cost-effective than MRI.• MRI is done if CT inconclusive ,single lesion ,

abnormal locations , hydrocephalus • Its imaging characterstics include 4 stages

• LIVING ( viable ) Stage : CT - appears as hypodense lesion

that doesn’t show ring enhancement or perilesional oedema“HOLE with DOT appearance ”Similar findings in T1w Images.

• COLLOIDAL Stage :MRI - represents the acute encephalitic phase of neurocysticerosis. Hence, its associated with perilesional edema and ring enhancement .

• NODULAR / GRANULAR Stage :MRI - single enhancing lesion

hypointense centre in T1 and T2 with hyperintense rim and surrounded by edema /gliosis.

• CALCIFIED Stage :Not visualised in MRICT- hyperdense nodules with no edema or enhancement.

TOXOPLASMOSIS

• CT - (70-80 % cases ) multiple B/L hypodense contrast enhancing focal lesions with predispostion to the basal ganglia and subcortical region.

A double dose contrast with increased delay scan time may increase the sensitivity.

• MRI -its more sensitive and hence the imaging of choice when an PLHA has CNS manifestations without any localizing sign.

its also indicated when there is single ring enhancing

Usual MRI findings

• On T1w - the lesions are hypointense • On T2w - lesions hyperintense , but they can

occasionally be isointense to hypointense.• Active lesions are often surrounded by

edema. • Post Gd - Focal nodular or ring enhancement

occurs in approximately 70% of patients.

CEREBRAL ABSCESS

USUAL MRI FINDINGS

• Abscess center is typically hypointense on T1-weighted images (T1WI) and hyperintense on T2-weighted images (T2WI); surrounding vasogenic edema has similar characteristics.

• Post Gd imaging : ring enhancement .• As the abscess matures, the capsule shows decreased low

T2 signal.• On trace DWI abscesses are typically hyperintense,

indicating decreased diffusion of water.

THANK – YOU.

REFERENCES :- HARRISON 17/eRADIOLOGY – David Sutton (2007 )TUBERCULOSIS ( M. Monir Madakour ) ( 2004 )ACTA TROPICA ( 87 ) (2003 ) (71 – 78 ) (review article )