MRI of the Brain Overview

MRI of the Brain

• This presentation details MRI procedures for brain imaging.
• The presenter is Dr. Hayder Jasim Taher, PhD of Medical Imaging, University of Hilla.

Anatomical Overview

• The nervous system is a complex network carrying messages to and from the brain and spinal cord to various body parts.
• It is divided into:
  • Central Nervous System (CNS): Includes the brain and spinal cord.
  • Peripheral Nervous System (PNS): Consists of nerves branching out from the brain and spinal cord, forming a communication network between CNS and body parts.
• The brain comprises three main parts:
  • Cerebrum: The largest part, consisting of two hemispheres with a cortex (grey matter - nerve cell bodies) and underlying white matter (nerve fibers).
  • Cerebellum: The second largest part, located in the posterior cranial fossa. It has an outer layer of grey matter and inner white matter.
  • Brainstem: Consists of the midbrain, pons, and medulla oblongata. It connects the cerebrum and cerebellum to the spinal cord. Contains ascending and descending tracts for communication.

Indications of Brain MRI

• MRI is a specialist investigation for neurological conditions.
• It's crucial for diagnosing:
  • Tumors (especially those in the posterior fossa, near the skull base, or pituitary fossa), where MRI is superior to CT in detecting these lesions.
  • Hemorrhage-Ischemic strokes, with MRI being effective at detecting thrombosis/stenosis (use of MR angiography).
  • Traumatic brain injuries (evaluating extracerebral collections and diffuse axonal injury). It can't visualize the bony cranium.
  • Degenerative diseases like multiple sclerosis, subcortical arteriosclerotic encephalopathy, gliosis, and syrinx.

MRI Procedure

• Patient Position:
  • Supine position (head first).
  • Placed in a head coil.
  • Well-padded to prevent image degradation from head movement.
  • If the coil has a mirror, the patient should be able to see out of the bore to address claustrophobia.
• Scout Slice Placement:
  • Sagittal localizer for axial slices (aligned parallel to a line joining the splenium and genu of the corpus callosum). Sagittal is also used for coronal slices (aligned parallel to the brainstem).
  • Axial localizers provide sagittal images.
  • Coverage for all slice types includes superior to inferior (Craniocervical junction to vertex), lateral to medial (Temporal lobes), and posterior to anterior (Occipital to frontal lobes).
  • Coronal and axial slices can also be obtained using coronal localizers.
• MRI Sequences (Routine Brain):
  • A table provides details about various sequences (e.g., sagittal T1, coronal T2, axial DWI, different FSE, SWI, post-contrast sequences). Specific timing information (TR, TE, FA, ETL) and slice thickness are included.

MRI Sequences (Routine brain) - Notes

• T1WI: Provides good anatomical images.
• Flair: Useful for identifying areas of edema, inflammation, and multiple sclerosis plaques.
• DWI: Preferable for stroke, abscesses, and cellular tumors due to restricted diffusion in those conditions.