Pediatric MRI of the Brain: A Primer

Kamakshya P. Patra; Jeffrey D. Lancaster; Jeffery Hogg; Jeffrey S. Carpenter

doi:10.1542/pir.35-3-106

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Kamakshya P. Patra, MD*
Jeffrey D. Lancaster, MD*
Jeffery Hogg, MD^†
Jeffrey S. Carpenter, MD^†

^*Department of Pediatrics, Section of Hospital Pediatrics, West Virginia University Children’s Hospital, Morgantown, WV.
^†Department of Neuroradiology, West Virginia University Health Sciences Center, Morgantown, WV.

Author Disclosure
Drs Patra, Lancaster, Hogg, and Carpenter have disclosed no financial relationships relevant to this article. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.

Abbreviations:

ADHD:: attention-deficit/hyperactivity disorder
CSF:: cerebrospinal fluid
CT:: computed tomography
DWI:: diffusion-weighted magnetic resonance imaging
FLAIR:: fluid-attenuated inversion recovery
fMRI:: functional magnetic resonance imaging
MRI:: magnetic resonance imaging
MRV:: magnetic resonance venography
NAA:: N-acetylaspartate
SDH:: subdural hematoma

Educational Gap

Because of recent advances in magnetic resonance imaging (MRI) techniques, pediatricians should be aware of the different modalities and their unique advantages and appropriateness in different clinical situations.

Objectives

After completing this article, readers should be able to:

Understand the pros and cons of MRI and computed tomography of the brain.
Know the basic principles of MRI and its different image modalities.
Be aware of the appropriateness of different modalities in specific clinical situations.

Introduction

Magnetic resonance imaging (MRI) is based on the absorption and emission of radiofrequency energy by hydrogen protons whose spin is influenced by changing magnetic fields (0.3 to 1.5 T). Unlike computed tomography (CT), there is no radiation exposure.

T1-weighted images cause fat (eg, myelin in white matter) to appear bright and water (eg, cerebrospinal fluid [CSF] or edema) to appear dark on this sequence. The gray-white interfaces of the brain are well depicted on these sequences, especially if with the images are thinly sliced. T2-weighted images cause water (eg, CSF and edema) to appear bright and fat to appear dark. The MRI-based intravenous contrast agents (eg, gadolinium) are frequently used in T1-weighted images (Fig 1A and B) to make serum appear bright. The blood-brain barrier typically serves to limit the passage of many molecules out of the blood vessels. If disease processes break down this barrier (such as infection, tumors, or inflammation), intravenous contrast agents can cross into the brain, causing areas of contrast entry to appear very bright.

Figure 1.

T1-weighted image at the level of midbrain. A. The cerebrospinal fluid (CSF) appears dark. B. The CSF appears bright. Note the gray and white matter differentiation …