62430340-MRI-brain.ppt

Brain MRI

Brain MRI

Indications :

1- Multiple sclerosis MS

2- Primary tumor assessment and metastasis.

3- evaluation of infarction.

4- Unexplained neurological symptoms and defect

Brain MRI Equipment : 1- Head coil (circularly

polarized (CP) head coils. These volume coils are closely shaped around the head of the patient. At best, CP coils provide a signal to- noise ratio (SNR) gain of √2 compared with non-CP coils

2- Immobilization pads 3- Ear plugs

Brain MRI

Patient position : Pt supine , head first within head coil ,

interpupillary line is parallel to table and head straight , the longitudinal alignment light with midsagittal line ,the horizontal one passes through the nasion .

Brain MRI protocol Technical Data : Excellent SNR and brain contrast is achieved.

Particularly using FSE with fine matrix , especially on T2 weighted images.

CSF has a long T1 recovery time and long T2 decay time therefore appear black low signal on T1 and white high signal on T2.

Protein within water (CSF) decreases T1 relaxation therefore produces a higher signal than pure CSF.

White matter on T1 weighted images produces a relatively high signal compared to grey matter.

On T2 weighted images white matter produces a lower signal , while grey matter produces a much brighter signal .

Brain MRI protocol ( Adults) 1. Localizer ( 3 planes or sagittal and axial)2. Axial T2 3. Axial T14. Axial FLAIR 5. Sagittal T26. Coronal T1 7. diffusion

Brain MRI protocol Axial sequence :

plot on sagittal plane, parallel to line through anterior and posterior commissure ,from the foramen magnum to vertex .

Brain MRI protocol Slice thickness : 5-6 mm Slice gap : 20% of the

slice thickness ( 1-1.2 mm) Saturation slab : parallel to

slices , inferior to most caudal slice 10 mm and thickness 50-80 mm

Brain MRI protocol T2 weighted :

FSE

TR : 3500-4500

TE : 100-120

Brain MRI protocol T1 weighted :

FSE or SE

TR : 450-600

TE :12-25

Brain MRI protocol Axial FLAIR :TR :9000TE :120TI :2300

FLAIR sequence Suppression of CSF

signal .it useful for preiventicular or cord lesions such as MS.

Brain MRI protocol Sagittal :

Brain MRI protocol Sagittal plot on

coronal and axial localizer .

Same slice thickness , gap and saturation slab .

T2 weighted: FSE TR : 3500-4500 TE:100

Brain MRI protocol Coronal sequence : Plot on sagittal

localizer Same parameters of

T1 sequence .

Brain MRI protocol

Coronal T1 image

Brain MRI protocol

Brain MRI protocol

Diffusion sequence •Excellent non-invasive method of measuring the

diffusion characteristics of biological tissue. •Based on Spin Echo. •Includes two additional large gradients around a

180 o pulse: -Static spins: dephasing of the spins due to the first

lobe is followed by an exact rephasing by the second lobe.

-Diffusing spins: rephasing will not be complete which results in a signal loss within a given voxel, in addition to T1- and T2-effects.

Brain MRI protocol Diffusion sequence : Important in the

investigation of early stroke , utilize in pediatric pt to investigate the effect of hypoxia and myelination pattern .

Brain MRI protocol ( Additional )

Diffusion sequence Very sensitive to motion of fluid molecules

Postprocessing ’Diffusion’ package to calculate parametric maps (e.g. ADC-, eADC-, FA-map).

•FiberTrak package to track fibers for diffusion tensor data with at least 6 diffusion directions.

Fiber track ( Additional )

Hemorrhage in brain MRI  Age Hyperacute ( < 24 hrs old )T1 :Hypointense T2 :Hyperintense Acute ( 1-3 days ), T1 :Hypointense T2 : Hypointense,

surrounded by hyperintense margin Subacute ( 4-14 days ), T1: Hyperintense,T2 : hypointense Chronic (> 14 days ) T1 :Hypointense T2 :hypointense margin

surrounding hyperintense fluid cavity

Hyperacute hemorrhage

Acute Hemorrgahe

Subacute Hemorrhage

Chronic Hemorrhage

Brain Infarction (stroke)

Magnetic resonance imaging in acute stroke. Left: Diffusion-weighted MRI in acute ischemic stroke performed 35 minutes after symptom onset. Right: Apparent diffusion coefficient (ADC) map obtained from the same patient at the same time.

MRA for Brain Time-of-flight (TOF) or Inflow

angiography, uses a short echo time and flow compensation to make flowing blood much brighter than stationary tissue. As flowing blood enters the area being imaged it has seen a limited number of excitation pulses so it is not saturated, this gives it a much higher signal than the saturated stationary tissue

Brain MRI protocol ( Tumors) Axial T1 ( HR) Axial T2 ( HR) Sagittal T2 Adminstration of 10 ml of Gd-DTPA ( 0.2 ml per kg ) Axial T1 Coronal T1 Sagittal T1

Brain MRI protocol ( Tumors)

Perfusion

Perfusion imaging

Perfusion imaging tracks the transient passage of a Gd-based contrast agent bolus by means of a fast dynamic scan:

•Contrast agent will be injected as a bolus.

•Simultaneously, a fast dynamic scan will be started.

•This dynamic scan will be evaluated with post-processing packages.

Perfusion image with pathology in left parietal area

Perfusion ( Additional )

Brain MRI protocol ( CPA)

(Cerebellopontine angle) Localizer 3 planes Axial T1 Axial T2 Coronal T1 Coronal T2 Post contrast T1 axial and coronal

Brain MRI protocol ( CPA) Axial sequence plot

on coronal localizer. Slice thickness :2-3

mm Slice gap : 20% of

slice thickness ( 1-1.2mm)

Sat. slab : inferior and superior .

Brain MRI protocol ( CPA) Definition : Acoustic schwannomas are

benign tumors of Schwann cells. Schwannomas typically involve the cranial nerves and most commonly the sensory nerves-VIII and V. Rarely there can be involvement of cranial nerve VII or the nerves within the jugular sheath ( IX, X, X1). Patients typically present with tinnitus or sensorineural hearing loss, although the mass typically arises from the vestibular portion of the nerve.

Radiographic appearance : MR demonstrates a T1

isointense (without gadolinium), intensely enhancing mass (with gadolinium ) extending into the internal auditory canal. The mass demonstrates increased signal with T2 weighting .

Brain MRI protocol ( CPA)

T1 Axial T1 axial with Gad.

Brain MRI protocol ( CPA)

T2 axial T1 with Gad coronal

Brain MRI protocol (MS) an autoimmune condition in which the

immune system attacks the central nervous system (affects principally the white matter in the brain and spinal cord ), leading to demyelination (which the myelin sheath of neurons is damaged ) MS affects the ability of nerve cells in the brain and spinal cord to communicate with each other

It is more common in females than males (3:2)

Brain MRI protocol (MS)

Routine brain Best with sagittal FLAIR ( HR) Adminstration of contrast

Brain MRI protocol (MS)

FLAIR Images:   Hyperintense lesion is noted in the pontine tectum at the floor of the fourth ventricle.

Brain MRI protocol (MS)

T2WI:   Large callosal-septal plaque. T2WI:   Callosal-septal plaques are hyperintense.

Brain MRI protocol (MS)

Postcontrast T1WI :   Enhancing lesion floor of 4th ventricle.

Brain MRI protocol (epilepsy) Axial T2 Plot on sagittal

parallel to temporal lobe .

Slice thickness 3mm Gap 1- 1.2 mm Sat slab .

Brain MRI protocol (epilepsy) Coronal sequence Plot on sagittal

perpendicular to line of hippocamaple grey matter.

Same slice thickness

TR :7000 TE: 40 TI : 400

Brain MRI protocol (epilepsy)

Coronal FLAIR

There is increased signal seen on both FLAIR image in the right hippocampus in comparison with the left. There is also evidence of asymmetry of tissue with loss of volume in the right hippocampus

Brain MRI protocol (Pituitary) Localizer Sagittal T1 ,T2 HR Coronal T1 HR Post contrast Coronal T1 Sagittal T1 Best with dynamic sequence

Brain MRI protocol (Pituitary) Coronal sequence Plot on

mediosagittal localizer superior to sella.

Slice thickness 2mm Gap : 0-20% of

thickness 2 sat. slab

Small FOV

Brain MRI protocol (Pituitary) Sagittal sequence Plot in coronal

localizer superior to sella

Same parameters

Brain MRI protocol (Pituitary)

T1 sagittal T1 sagittal post contrast

Brain MRI protocol (Pituitary)

Orbit MRI protocol

Scout 3 planes Axial T1 , T2 HR Coronal T1 ,T2 HR Axial Fat sat. Parasagittal T2

Orbit MRI protocol Coronal Plot on axial

localizer 3mm slice thickness Gap 20%

Orbit MRI protocol Axial plot on coronal

localizer 3mm slice thickness Gap 20%

Orbit MRI protocol Parasagittal : Plot on axial along

with optic nerve 3mm slice thickness Gap 20%

Spectroscopy MRI ( Additional )

Functional MRI ( Additional )BOLD imaging