Cerebral Abscess MRI Protocol

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Plain "Cerebral Abscess MRI Protocol"

• T1-Sagittal head
• T1 SE-Axial head
• FLAIR Axial head
• T2 FSE Axial head
• DWI/ADC

Post Contrast "Cerebral Abscess MRI Protocol"

• T1 SE-Axial post-gadolinium (This is essentially the same sequence as the pre-gadolinium scan, but can be performed with the addition of a flow compensation (FC) pulse to better delineate the cerebral vessels, and a magnetization transfer (MT) pulse to optimize enhancing lesion detection.)
• T1-coronal post-gadolinium head
• MR perfusion
• MR spectroscopy  

Radiology notes:"Cerebral Abscess MRI Protocol"

MR perfusion : rCBV is reduced in the surrounding oedema c.f. to both normal white matter and tumour oedema seen in high grade gliomas .

MR spectroscopy : elevation of a succinate peak is relatively specific but not present in all abscesses ; high lactate, acetate, alanine, valine, leucine, and isoleucine levels peak may be present ; Cho / Crn and NAA peaks are reduced.Magnetic resonance (MR) spectroscopy may be helpful in the differential diagnosis of toxoplasmosis versus CNS lymphoma. CNS lymphoma generally shows a mild pattern of elevated lipid and lactate peaks, with a prominent choline peak with some other normal metabolites. In toxoplasmosis, there are elevated lipid and lactate peaks, while other normal brain metabolites are nearly absent.

Diffusion-weighted MRI may be useful in differentiating abscess MRI features from necrotic tumor. 

Brain Abscess MRI findings Classification

• Early cerebritis stage-The early cerebritis stage presents as an ill-defined subcortical hyperintense zone that can be noted on T2-weighted imaging. Contrast-enhanced T1-weighted studies demonstrate poorly delineated enhancing areas within the isointense to mildly hypointense edematous region.
• Late cerebritis stage-During the late cerebritis stage, the central necrotic area is hyperintense to brain tissue on proton-density and T2-weighted sequences. Peripheral edema is common. The rim enhances intensely following contrast administration. Satellite lesions may be demonstrated.
• Early and late capsule stages-During the early and late capsule stages, the collagenous abscess capsule is visible prior to contrast as a comparatively thin-walled, isointense to slightly hyperintense ring that becomes hypointense on T2-weighted MRIs.Diffusion-weighted imaging aids in depiction of specific features of a brain abscess. If a cerebral abscess ruptures into the ventricular system, diffusion-weighted images demonstrate specific patterns.Purulent material within the ventricle appears similar to that of the central abscess cavity, with a strongly hyperintense signal on diffusion-weighted images.

MRI Features in different Stages

Early cerebritis: swollen, edematous, areas of necrosis, ill-define margins; nonspecific (tumor, infarct)

Late cerebritis: increased central necrosis, thick irregular contrast enhancement, high on FLAIR, T2, and DWI

Early capsule: within 2 weeks, walled off capsule, necrotic center, enhancing rim

Late capsule: more defined rim, multiloculated, capsule is low on T2, markedly high on DWI