Brain Scan - MRI

Wednesday, August 31, 2016

Head Scan MRI

Brain MRI are usually done with the patient supine on the examination couch with their head within the head coil. The head is adjusted so that the interpupillary line is parallel to the couch and the head is straight. The longitudinal alignment light lies in the midline of the patient, while horizontal alignment light passes through the nasion. Straps and foam pads are used for immobilization. Brain MRI is done  to diagnose these common indication:

  • Multiple Sclerosis (MS)
  • Primary tumour assessment and or metastatic disease.
  • AIDS (toxoplasmosis)
  • Infarction – cerebral vasvular accident (CVA) vs Transient ischaemic attack (TIA)
  • Haemorrhage
  • Hearing Loss
  • Visual disturbances
  • Infection
  • Trauma
  • Unexplained neurological symptoms or deficit
  • Pre-operative Planning
  • Radiation Treatment Planning
  • A Follow-up after surgical or treatment

Equipment Needed when performing Brain MRI:

  • Head Coil (quadrant or multi-coil array)
  • Immobilization pads and straps
  • Ear plugs
  • High performance gradients for EPI, diffusion and perfusion imaging

Suggested Protocol Head / Scan MRI

Head scan MRI

Sagittal SE T1 weighted midline slice 
of the brain showing the axis of the
anterior and posterior commissures

Sagital SE / FSE Incoherent (spoiled) GRE T1

The medium slices or gap are prescribed on each of the longitudinal alignment light from one temporal lobe to the other. The area from the foramen magnum to the top of the head is included in the image. Left is 37 mm to Right 37 mm.
Axial or Oblique SE / FSE PD / T2
Medium slices or gap are prescribed from the foramen magnum to the superior surface of the brain. Slices may be angled so that they are parallel to the anterior and posterior commissure axis. This enables precise localization of lessions from reference to anatomy atlases. Many sites have replaced the PD sequence with FLAIR. SS-FSE or SS-EPI may be a necessary alternative for a rapid examination in uncooperative patients.

Coronal SE / FSE PD / T2

As for axial PD / T2, except prescribe slices from the cerebellum to the frontal lobe.
axial oblique t2 head scan mri
Axial/oblique FSE
T2 weighted image of the brain
showing normal appearances

Additional Sequences MRI Head Scanning

Axial or Oblique IR T1

Slice prescription as for Axial / oblique T2

This sequence is very useful in imaging of the pediatric brain. White matter does not fully myelinate until approximately 5 years of age, therefore in the very young patient, grey and white matter have very similar T1 relaxation times, and the CNR between these tissues is small on SE T1 sequences.

head scan MRI
FLAIR image of the brain.

Axial or Oblique FLAIR / EPI

This sequence provide a quick acquisition with stoppage of CSF signal. It very useful in studying periventricular or cord lesions like MS plaques. Periventricular abnormalities will have a high signal intensity in contrast to the low signal of CSF which has been nulled using a long TI as shown in the image of Axial or Oblique FLAIR brain scan.

head scan MRI
incoherent (spoiled) GRE image
of the brain.

Axial / Oblique SE / FSE Incoherent (spoiled) GRE T1

A brain scan sequence for Pre and Post contrast brain scans are common especially for turn assessment.

brain scan mri
weighted image of the brain.

SS – FSE T2 Brain Scan

A brain scan MRI and very useful for rapid imaging if the patient in uncooperative. In the image shows a weighted image of the brain. MRI scan of entire brain with SS – FSE T2.

Axial 3D incoherent (spoiled) GRE T1 Brain Scan

It is a high resolution imaging sequence and useful for imaging of small structures in the brain. An isotropic dataset must be acquired when reformatting of desired slices.

Axail Oblique GRE / EPI T1 and T2

If demonstration of hemorrhage is it better than SE and FSE. Due to sensitivity of magnetic susceptibilities.

Axial or Oblique SE MT

Slice prescription as for Axial oblique T2. MT is a useful sequence to improve visualization of lesions like as metastasis, and other low grade tumors but, 30 – 40 % of grey and white matter loss its signal when this MT pulse sequence is used. The CNR between lesions and the surrounding brain is therefore increased.

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