Magnetic Resonance Imaging

MRI provides the following advantages:

• No ionizing radiation exposure (especially important in multiple follow-up examinations)

• Greater sensitivity in detection of brain tumors especially in the temporal lobe and posterior fossa (these lesions are obscured by bony artifact on CT)

• Ability to directly image in multiple planes (multiplanar), which is of value to neurosurgical planning (CT is usually only in axial planes)

• Ability to apply different pulse sequences, which is useful in depicting anatomy (Tj-weighted images) and pathology (T2-weighted images)

• Ability to map motor areas with functional MRI.

MRI specificity is enhanced with the contrast agent gadolinium diethylenetri-aminepentaacetic acid dimeglumine (Gd-DTPA), which should be used in the evaluation of childhood CNS tumors and has the following advantages:

• Highlights areas of blood-brain barrier breakdown that occur in tumors

• Useful in identifying areas of tumor within an area of surrounding edema

• Improves the delineation of cystic from solid tumor elements

• Helps to differentiate residual tumor from gliosis (scarring).

The major difficulty with MRI in infants and children is the long time required to complete imaging and for this reason adequate sedation is required.

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