intro neuro mri

8/3/2019 Intro Neuro Mri

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INTRODUCTION TONEURO MR

Dr. Francis Neuffer

USC School of Medicine

Department of Radiology


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MR IMAGING

Based on behavior ofprotons exposed to a

magnetic field and a radiowave

T1, T2, FLAIR, Diffusion,

Gadolinium enhanced, andAngiography are specifictypes of Neuro imagingsequences.


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RF


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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


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MAGNETIC RESONANCE IMAGING

Limitations

1. ICU patients and Claustrophobia2. Metal artifact

1. RF Energy pacemaker override

2. Magnetic field - aneurysm clips - ocular metal

-missile effect

3. Nephrogenic Systemic Fibrosis-

gadolinium toxicity in renal failure


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Child Dies in MRI MachineThe Associated Press

Monday, July 30, 2001: 2:42 p.m. EDT

A child undergoing an MRI exam received a

fatal head wound when the machines powerfulmagnet pulled a metal oxygen canister inside.


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GADOLINEUM TOXICITY


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MAGNETIC RESONANCE IMAGING

Advantages

1. Multiple signal sources

2. No iodine toxicity/allergy issues

3. No ionizing radiation issues


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MR HAS ADVANTAGE OFMULTI PLANAR IMAGING


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MRI INDICATIONS

Ischemia

Tumor Infection

Dating blood products

Congenital abnormalities


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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


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T1 SCAN T2 SCAN

MR SIGNAL

Tissues resonate a signal based on their intrinsic T2 time.

Tissues recover their magnetization based on intrinsic T1 time.


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T1 SCAN

T2

SCAN

Anatomic structures

Fat = bright

Water = hypo intense

Water weighted sequence

Water = bright

Fat = relatively hypo intense

Good for identifying pathology


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MRI FINDINGS OF ACUTE ISCHEMIC

STROKE

T1 (hypo intense) FLAIR (hyper intense)T2 (hyper intense)

FLAIR SCANS ARE T2 SCANS WITH THE FREE

WATER SIGNAL NULLED.


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MRI FINDINGS OF ACUTE STROKE

T1 (hypo intense)

FLAIR (hyper intense)

T2 (hyper intense)

Diffusion (hyper intense)


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DIFFUSION IMAGING

DIFFUSION IMAGING SEPARATES INFARCTIONON ACUTE OR CHRONIC BASIS

THE ACUTE INFARCT HAS A DIFFERENTDIFFUSION SIGNAL DUE TO INTRACELLULAR

EDEMA


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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


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MRI ACUTE STROKE

T1

T2

DiffusionPCA DISTRIBUTION


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MRI

OLD -VS- NEW

ISCHEMIC INFARCT

T1 T2 DIFFUSION


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4th ventricle

4th ventricle

Pons

Pons

Temporallobe

Occipital

lobe

Temporal

lobeBasillarartery

Middle

Cerebellar

peduncle

ANATOMY


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ANATOMY

Supracellar

cistern MiddleCerebral

artery

Cerebral

peduncleAqueduct

Of Sylvius

TemporalHorn lateral

venticle

Optic

chiasm


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Putamen

Globus

pallidus

Caudate

head

Thalamus

ALIC

PLICPLIC

ALIC

Middle

Cerebral

artery

Corpus

callosum

External

capsule

ANATOMY


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ANATOMY

Corpus

callosum

Lateral

ventricleCorona

radiata

AnteriorCerebral

artery

Middle

Cerebral

artery

Occipital

lobe

Parietal

lobe

Frontal

lobe


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ANATOMY

Centrum

Semiovale


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ENHANCED SCANSBLOOD/BRAIN BARRIER DISRUPTION

IDENTIFY PATHOLOGY

ARTERIOGRAM EFFECTS

GADOLINEUM IMAGING

MR CONTRAST

CT WITH CONTRAST ENHANCEMENT


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CT WITH CONTRAST ENHANCEMENT

ENHANCING RING LESION

NON ENHANCED


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T1- SCAN WITHOUT GADOLINEUM

T1 SCAN WITH GADOLINEUM

T2- SCAN

MR


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NORMAL

ABNORMAL

PITUITARY

ADENOMA


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T1 SAGITTAL MR

WITHOUT GADOLINEUM WITH GADOLINEUM


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ACOUSTIC

NEUROMA

WITH GADOLINEUMWITHOUT GADOLINEUM

VASCULAR ANATOMY


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VASCULAR ANATOMY

CCA

ICA

ECA

Cavernous

Carotid

CCA

ICA

Vertebral

artery

Basilar

artery

Middlecerebral

Carotid

bulb

Anterior cerebral

ECA

MR ARTERIOGRAM


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VASCULAR ANATOMY

Cavernous

carotid

MCABA

ACA

Basilar

artery

Anterior

cerebral

MCACavernous

carotid

ECA

ICA

Vertebral

TIME OF FLIGHT MRA

TOF-MRA


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VASCULAR ANATOMY

MCA

ACoA

ACA

ICA PCoA

Basilar Artery

Circle of Willis

PCA


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VASCULAR DISTRIBUTIONS

MCA

ACA

PCA


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STROKE

Ischemic

Large artery atherosclerosis

Higher mortality

Cardioembolism

Recurrence

Small vessel ischemia Occlusion of small end arteries

Predilection for BG, IC, Pons, Corona Radiata

Hemorrhagic


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IMAGING OF STROKE

CT

Better identification of acute hemorrhage

Availability Decrease expense

Decrease time

Less contraindications

MRI

More sensitive to early changes of stroke ie.edema


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CT FINDINGS SAH


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STROKE INTERVENTION

THROMBOLYTIC THERAPY TO SALVAGE

ISCHEMIC BRAIN AT THE BORDER OF THEINFARCT ZONE

WHO BENEFITS AND HOW SELECT?


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TIME CONSTRAINTS

3-6 HOUR WINDOW

RISK OF HEMORRAGIC CONVERSION

WITH THROMBOLYTIC THERAPY

STROKE INTERVENTION


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RTLT


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MR PERFUSION

Gadolineum Injection


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CT PERFUSION

Iodine Injection


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COMPARISON OF INFARCT

ZONE AND ISCHEMIC ZONE

TO IDENTIFY TREATMENT CANDIDATES

GOAL FOR IMAGING


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MRI FINDINGS OF ACUTE STROKE

T1 (hypointense) T2 (hyperintense)

intro neuro mri

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