acknowledgements - indiana university …mri/seminars/slides/spring 2014/neurovascular mra...anatomy...

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E. Michael Harned, M.D. Assistant Professor of Clinical Radiology Indiana University School of Medicine

I have nothing to disclose

Neurovascular Magnetic Resonance Angiography And Magnetic Resonance Venography

ACKNOWLEDGEMENTS

1. Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC: Bradley’s Neurology in Clinical Practice, 6th ed. Saunders

2. Anderson CM, Edelman RR, Turski PA: Clinical Magnetic Resonance Angiography. Raven Press

For neurovascular imaging, MRA has largely been replaced by CTA due to its higher spatial resolution and relatively fewer artifacts.

However, MRA may still be desired in certain situations:

Patients with a contraindication to iodinated contrast administration: history of anaphylactoid reaction, severe asthma, renal insufficiency, multiple myeloma

Lack of venous access

Patients having an MRI of the brain, neck, or cervical spine where it is desired to get vascular imaging done at the same time- “killing 2 birds with 1 stone”

NEUROVASCULAR ANATOMY

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MRA TECHNIQUES

Time-Of-Flight (TOF)

Relies on repeated saturation pulses to a slice or volume so that background tissue is suppressed and only new spins (flow) are able to generate signal

May be performed as a 2D or 3D technique

2D examines a single slice at a time and then stacks them

3D examines a slab and uses phase-encoding along the Z-axis

3D TOF allows better spatial resolution but is more

susceptible to signal loss due to in-slab flow

RF Pulse

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SATURATION INCREASES WITH:

Shorter TR

Larger flip angle

Multiple repetitions

Longer T1

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Phase-Contrast

Relies on bipolar gradient pulse which causes phase shift for flowing spins but no phase shift for stationary spins

Excellent background suppression

No need for saturation band

Also provides information on flow direction

May be performed as a 2D or 3D technique

3D Phase-Contrast allows better spatial resolution and provides flow direction information along all 3 axes

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Contrast-Enhanced MRA

Really a form of 3D TOF MRA but uses gadolinium to increase intravascular signal and overcome problem of signal loss due to in-slab flow

Images acquired quickly while a bolus of gadolinium is in the vessels of interest

Different physics- uses elliptical-centric k-space filling:

Central (most important) points of k-space are filled first, at time of greatest intravascular gadolinium concentration

May acquire preinjection source images as mask for subtraction- “Digital Subtraction MRA”

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ATHEROSCLEROTIC STENOTIC DISEASE

WHY IT MATTERS (all numbers approximate and for United States)

795,000 people suffer new or recurrent stroke each year

1 stroke every 40 seconds

Stroke kills more than 137,000 people per year.

1 stroke death every 4 minutes

#4 cause of death

1 in every 18 deaths

Stroke death rates per year per 100,000 population: 41.7 for white males 41.1 for white females 67.7 for black males 57.0 for black females

Americans pay about $73.7 billion per year for stroke-related medical costs and disability

Likely Histories/Indications:

Stroke, CVA, or TIA

Specific neurologic deficit- hemiparesis, aphasia, facial numbness, etc.

Carotid bruit

ICA stenosis on carotid ultrasound

WHAT THE RADIOLOGIST NEEDS FROM YOU

3D TOF MRA of the circle of Willis

Contrast-enhanced MRA of the arteries of the neck (Often a good idea to do a 2D TOF MRA of the neck first in case there is a problem with the gadolinium bolus- There is no going back and doing this once contrast has been injected)

Please send both sets of source images as well as rotating segmented MIPs of right carotid, left carotid, and vertebrobasilar for circle of Willis and for neck

3D TOF MRA circle of Willis- source images

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3D TOF MRA circle of Willis- MIPs Contrast-enhanced MRA neck- source images Contrast-Enhanced MRA neck- MIPs

2D TOF MRA neck- source images 2D TOF MRA neck- MIPs

Carotid stenosis%= (1 • Nto) x 100

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Figure 1. A 58-year-old man with truncus bicaroticus as normal variant that is displayed both on

MRA and DSA (a and b; arrow heads), and 90% diameter stenosis of the right ICA diagnosed on

MRA (c; bold arrow) and confirmed by DSA (d; bold arrow).

Willinek W A et al. Stroke. 2005;36:38-43

Copyright © American Heart Association, Inc. All rights reserved.

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Figure 2. Enlarged MIP image from CE MRA (a) and DSA image (b) of the circle of Willis of a 44-

year-old man: 50% stenosis in the M1 segment (arrow heads) of the right MCA was concordantly

diagnosed on MRA and DSA.


NON-ATHEROSCLEROTIC STENOSIS


Trauma

Neck pain

Specific neurologic deficit

Drug abuse

Protocol for evaluation same as for atherosclerotic stenosis

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Figure 4. A 61-year-old man patient with subacute right MCA territory infarction. 75% stenosis of

right ICA was diagnosed on CE MRA (a; arrow), but DSA revealed a thrombus causing a 55%

diameter stenosis (b; arrow).



Date of download: 12/22/2013 Copyright © 2012 American Medical

Association. All rights reserved.

From: Cocaine-Induced Cerebral Vasoconstriction Detected in Humans With Magnetic Resonance Angiography

JAMA. 1998;279(5):376-380. doi:10.1001/jama.279.5.376

Figure Legend:

Axial maximum intensity projection images at baseline (left) and20 minutes following intravenous cocaine (0.4 mg/kg) administration

(right).Cocaine induced a signal loss at distal segments of the middle cerebral arteries(upper arrowheads) and in the posterior

cerebral arteries (lower arrowheads),indicative of vasoconstriction. A indicates anterior; P, posterior; L, left;and R, right. Scale bar =

1 cm.

Moyamoya Disease

Disease where vessels at the base of the brain become constricted- Most commonly distal internal carotid arteries but may also involve proximal middle and anterior cerebral arteries

Collateral circulation develops around the blocked vessels, but the collateral vessels are small, weak, and prone to hemorrhage

On angiography, the collateral vessels resemble a “puff of smoke”- “Moyamoya” in Japanese

Patients present with TIAs, strokes, headaches, and seizures

Most common in women in their 20s and 30s

Association with Down’s syndrome, neurofibromatosis type 1, sickle cell disease, prior brain radiation

Figure 3. A 45-year-old woman with Moyamoya disease.



INTRACRANIAL ANEURYSMS

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Subarachnoid hemorrhage

Headaches

Family history of intracranial aneurysms

Autosomal dominant polycystic kidney disease


3D TOF MRA of the circle of Willis

No need for gadolinium

No need to image the neck

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VENOUS PATHOLOGY


Possible venous sinus thrombosis- pregnancy, oral contraceptives, cancer, other hypercoagulable states

Cavernous sinus syndrome

Hyperdense dural venous sinus or intracranial vein on CT

Venous infarct on CT or MRI

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2D TOF of the head

No need for gadolinium

No need to image the neck

2D TOF MRV head- source images 2D TOF MRV head- MIPs

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Thanks!

Questions?

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