neuro no audio

INTRODUCTION TO
NEURO MR

Dr. Francis Neuffer
USC School of Medicine
Department of Radiology


MR IMAGING
• Based on behavior of
protons exposed to a
magnetic field and a radio
wave
• T1, T2, FLAIR, Diffusion,
Gadolinium enhanced, and
Angiography are specific
types of Neuro imaging
sequences.




RF


MR INTERPRETATION
• Symmetry
• Identify normal structures
– Ventricles
– Grey matter structures
– White matter tracts

– Language – Intensity/ Signal
– Description of tissue signal on various different scanning
sequences ie.
– T1 T2 Flair Diffusion Gadolinium


MAGNETIC RESONANCE IMAGING
Limitations
1. ICU patients and Claustrophobia
2. Metal artifact
1. RF Energy – pacemaker override
2. Magnetic field - aneurysm clips - ocular metal
-missile effect
3. Nephrogenic Systemic Fibrosisgadolinium toxicity in renal failure


Child Dies in MRI Machine
The Associated Press
Monday, July 30, 2001: 2:42 p.m. EDT

A child undergoing an MRI exam received a
fatal head wound when the machine’s powerful
magnet pulled a metal oxygen canister inside.


GADOLINEUM TOXICITY


MAGNETIC RESONANCE IMAGING

Advantages
1. Multiple signal sources
2. No iodine toxicity/allergy issues
3. No ionizing radiation issues


MR HAS ADVANTAGE OF
MULTI PLANAR IMAGING


MRI INDICATIONS
•
•
•
•
•

Ischemia
Tumor
Infection
Dating blood products
Congenital abnormalities


MRI INTERPRETATION
• Pulse Sequences− T1 weighted-- (Fat, Melanin, Hemosiderin,
Methemoglobin= bright)
− T2 weighted-- (Water, Oxyhemoglobin, Hemosiderin=
bright)
− FLAIR-- (Pathology bright, CSF dark)

− Diffusion Weighted- recent infarction bright


MR SIGNAL
T1 SCAN

T2 SCAN

Tissues resonate a signal based on their intrinsic T2 time.
Tissues recover their magnetization based on intrinsic T1 time.


T1 SCAN
Anatomic structures
Fat = bright
Water = hypo intense

T2
SCAN
Water weighted sequence
Water = bright
Fat = relatively hypo intense
Good for identifying pathology


MRI FINDINGS OF ACUTE ISCHEMIC
STROKE

T1 (hypo intense)

T2 (hyper intense)

FLAIR (hyper intense)

FLAIR SCANS ARE T2 SCANS WITH THE FREE
WATER SIGNAL NULLED.


MRI FINDINGS OF ACUTE STROKE

T1 (hypo intense)

FLAIR (hyper intense)

T2 (hyper intense)

Diffusion (hyper intense)


DIFFUSION IMAGING

• DIFFUSION IMAGING SEPARATES INFARCTION
ON ACUTE OR CHRONIC BASIS
• THE ACUTE INFARCT HAS A DIFFERENT
DIFFUSION SIGNAL DUE TO INTRACELLULAR
EDEMA


DIFFUSION IMAGING
• Increased sensitivity for early changes of

edema
– Becomes abnormal within 30 mins.
– Ischemia Cellular Dysfunction
Increased
Intracellular Space
Restricted Diffusion of
Water Increased signal

• Distinguish b/w old and new stroke
• New stroke = bright on DWI (diffusion weighted image)
• Old stroke (encephalomalacia) = low SI on DWI


MRI ACUTE STROKE

T1

T2

PCA DISTRIBUTION

Diffusion


MRI
OLD -VS- NEW
ISCHEMIC INFARCT

T1

T2

DIFFUSION


ANATOMY

Temporal
lobe
Pons

4th ventricle

Middle
Cerebellar
peduncle
Occipital
lobe

Temporal
lobe
Pons
4th ventricle

Basillar
artery


ANATOMY

Supracellar
cistern

Aqueduct
Of Sylvius

Middle
Cerebral
artery
Cerebral
peduncle
Temporal
Horn lateral
venticle

Optic
chiasm


ANATOMY

ALIC
Middle
Cerebral
artery
PLIC

Corpus
callosum

Caudate
head
External
capsule
Thalamus

ALIC
Putamen
Globus
pallidus
PLIC


ANATOMY
Frontal
lobe
Middle
Cerebral
artery

Corona
radiata

Corpus
callosum
Lateral
ventricle
Parietal
lobe
Occipital

lobe

Anterior
Cerebral
artery