Download TOF Phase Contrast

Pictorial review of intracranial MRV
techniques, pitfalls, and common
pathologies involving the cerebral
venous system
Jennifer Trinh, MD
Rajul Pandit, MD
Mahesh R. Patel, MD
Santa Clara Valley Medical Center, San Jose, CA
Control #806
eEdE-44
Disclosures
• There are no financial disclosures.
Objectives
• Know the advantages and disadvantages of two noncontrast based MR venography (MRV) techniques and
their pitfalls
• Review the anatomy of the cerebral venous system
• Know the common sites of cerebral venous thrombosis
(CVT)
• Illustrate common etiologies of CVT and occlusion
Introduction
• The cerebral venous system can be difficult to
evaluate due to artifacts, variant anatomy, and
overlapping signal intensities of venous flow.
• Several MRV methods are available to image the
intracranial venous system.
• These methods include both non-contrast and
contrast based techniques.
MRV Techniques
• Two non-contrast based MRV techniques are
utilized at our institution.
– 2-D time of flight (TOF) MRV is obtained with the
source data in the coronal plane.
– 3-D phase contrast MRV is obtained with the source
data in the sagittal plane.
• Contrast-enhanced MRV is another technique
that is used at other institutions.
– This technique relies on the paramagnetic effect of
intravenous gadolinium to shorten T1 and provide
intravascular contrast enhancement.
Signal Generation in Non-Contrast
MRV
• Time of Flight
– TOF uses flow phenomenon for signal generation. Blood flowing
into the slice is not saturated and appears bright relative to the
dark (suppressed) background. A saturation band is applied
above the slice to suppress inflowing arterial signal.
• Phase Contrast
– Spins that are moving in the same direction as a magnetic field
gradient develop a phase shift that is proportional to the
velocity of the spins. Bipolar gradients (two gradients with
equal magnitude but opposite direction) are used to encode the
velocity of the spins.
– The signal in the vein depends on the velocity of the flowing
blood and the velocity encoding by the technician.
Comparison of MRV Techniques
Technique
Advantages
Disadvantages
TOF
• Shorter imaging time
• More prone to false-positives
• No special pulse sequences are
from in-plane flow
required
Phase contrast
• Better background suppression • More sensitive to motion
• Can detect flow in all 3
artifacts and turbulent flow
orthogonal planes
• More arterial signal
• Better flow quantification
• No false-negatives due to
methemoglobin
Contrast enhanced
• Less likely to give falsepositives due to slow or
complex flow
• Potential false negatives due
to methemoglobin or
enhancing chronic thrombus
Anatomy
TOF
Phase Contrast
Superior Sagittal Sinus
Superior Sagittal Sinus
Vein of Galen
Vein of Galen
Internal
cerebral
vein
Internal
cerebral
vein
Internal
jugular
veins
Transverse
sinus
Sigmoid
sinus
Internal
jugular
vein
Transverse
sinus
Sigmoid
sinus
Cerebral Venous System &
Most Frequent Location of Thrombosis
TOF
Phase Contrast
Superior Sagittal Sinus
Superior Sagittal Sinus (62%)
Cortical veins
(17%)
Vein of Galen
Vein of Galen
Internal
cerebral
vein
Internal
cerebral
vein
(12%)
Internal
jugular
veins
(12%)
Transverse
sinus (45%)
Sigmoid
sinus
Internal
jugular
vein
Transverse
sinus
Sigmoid
sinus
ARTIFACTS
In Plane Flow Artifact
TOF
In flow signal loss in the distal
SSS in TOF sequence
Phase Contrast
Phase contrast imaging shows
the SSS is patent
Teaching Points:
Common sites of signal loss
include:
• The distal portion of the SSS,
which is located in the
coronal plane, on coronal
TOF MRV.
• The horizontal portion of the
SSS, the junction of the vein
of Galen with the straight
sinus, and the portions of
the transverse sinus that are
located in the axial plane on
axial TOF MRV.
Obscuration of the internal cerebral
veins by arterial inflow
TOF
Internal
cerebral
veins
Phase Contrast
Only one internal cerebral
vein is visualized. The other
is obscured by arterial inflow
Arterial
inflow in
carotids
Arachnoid Granulations
Phase Contrast
Well defined extrinsic filling
defect in the right transverse
sinus
TOF
TOF Source Data
Teaching Points:
• Arachnoid granulations are small
protrusions through the dura
mater.
• They occur throughout the dural
sinus, but most commonly in the
transverse and superior sagittal
sinus.
• Imaging shows a focal, welldefined, round filling defect with a
characteristic anatomic
distribution.
• Normal patent flow immediately
proximal and distal to the filling
defects further supports arachnoid
granulations.
Hypoplastic transverse sinus
TOF
Apparent signal loss in the transverse
sinus is due to hypoplastic sinus
Source TOF data shows a hypoplastic sinus
Phase Contrast
Hypoplastic right transverse
sinus on phase contrast
Teaching Points:
• Hypoplasia or aplasia of one of the transverse sinuses is common.
• Do not mistake for a sinus thrombosis!
• Evaluate the source data.
• If there is a CT, evaluate the jugular foramen size. A hypoplastic transverse
sinus will also have a small jugular foramen.
PATHOLOGIES
Venous Sinus Thrombosis
64 year old female
with headaches.
Teaching Points:
• Mechanisms that lead to
cerebral venous thrombosis
include direct involvement of the
dural sinus (e.g. infection,
trauma, tumor infiltration),
hypercoagulable states,
increased blood viscosity (e.g.
dehydration), or venous stasis.
•
Absence of a flow void and the
presence of abnormal signal in
the sinus is a primary finding of
thrombosis on MRI. This should
be further evaluated by MRV as
slow or turbulent flow can also
cause abnormal signal.
•
An acute thrombus can be very
hypointense on T2 and mimic a
flow void.
Normal right
transverse sinus
flow void
Abnormal low T2 signal in the left
lateral transverse sinus.
Left lateral transverse, sigmoid,
and IJ are not seen, consistent
with thrombosis.
Cortical Vein Thrombosis due to
Spontaneous Intracranial Hypotension
46 year old female with orthostatic
headaches for 10 days.
CT: Dense cortical veins.
Sag T1W: Sagging of cerebellar tonsils and posterior
fossa structures with crowding of foramen magnum.
Axial GRE, FLAIR, T1WC+: blooming in the thrombosed
cortical veins, subarachnoid hemorrhage in the parietal
lobes, subdural hematomas, slit-like ventricles, and
diffuse dural enhancement.
Cortical Vein Thrombosis due to
Spontaneous Intracranial Hypotension
Dilated
cortical vein
No deep venous sinus thrombosis.
Multiple dilated cortical veins along convexity.
Teaching Points:
• Dense cortical veins (cord sign) on CT is
a sign of cortical venous thrombosis.
•
Imaging signs of intracranial
hypotension include diffuse cerebral
edema, cerebellar tonsillar herniation,
sagging of the brainstem, and dural
enhancement.
•
Undiagnosed intracranial hypotension
can result in subdural hematomas,
subarachnoid hemorrhage, and dural
venous sinus thrombosis.
•
Isolated cortical vein thrombosis is rare.
It may be associated with coagulation
abnormalities or chronic inflammatory
conditions such as inflammatory bowel
disease.
Venous Infarction
2 day old term infant with
ongoing dusky spells of
unclear etiology.
Marked restricted
diffusion in the
temporal lobe,
consistent with acute
infarction.
T1 hypointense, T2 hypointense signal with the area of infarction with blooming on GRE, consistent with
hemorrhagic venous infarction. Venous infarcts often present with hemorrhage in the acute setting.
Hemorrhagic transformation of an arterial infarct is less common and usually occurs later.
Venous Infarction & Thrombosis
MRV from the same
patient.
TOF
Artifactual loss of signal in the
posterior SSS on TOF. SSS is
patent on 3D velocity imaging.
Filling defect in the left transverse
sinus, consistent with thrombus.
Phase Contrast
Hypoplastic left sigmoid sinus and IJ vein,
better seen on phase contrast MRV.
Teaching Points:
• Suspect venous infarct in a young patient, if the infarct does not correspond to a a
vascular territory, if there is a round area of hemorrhage, if it spares the cortex, or
is in a bilateral parasagittal location.
• Evaluate the venous sinuses for a thrombus if there is a venous infarct.
Venous thrombosis due to venous
epidural hematoma
15 year old male
brought in after
a gang fight.
Occipital fracture causing a
venous epidural hematoma
Probable clot in the right
transverse and sigmoid sinus
junction
Active venous hemorrhage
within the epidural hematoma
Normal left venous sinuses
Medial aspect of right
transverse sinus not
visualized and may be
injured.
Venous thrombosis due to venous
epidural hematoma
MRV from the
same patient.
Occlusion of the right transverse venous
confluence.
Cervical portion of left IJ vein not visualized and
may be narrowed or occluded. There is an
emissary vein providing an alternative drainage.
Source data shows the distal right transverse
sinus is diminutive, but patent.
Mastoiditis with Right Internal Jugular
Vein Thrombosis
Attenuated transverse
& sigmoid sinuses
No signal in
right IJ vein
Thrombosed
right IJ vein
Flow present
proximal to
thrombosis
Normal
left IJ vein
Normal
left IJ vein
No signal in
right IJ vein
Normal
left IJ vein
Teaching Points:
• Venous sinus thrombosis is a complication
of mastoiditis, although the incidence has
declined due to antibiotic therapy.
• The sigmoid sinus and internal jugular vein
should be carefully evaluated for
thrombosis.
Compression from a Meningioma
T1WC+: Homogenously enhancing left parafalcine extraaxial mass that compresses the sagittal sinus at its dural
attachment.
CTV: Left parafalcine meningioma
compressing the sagittal sinus.
Difficult to exclude focal thrombosis
or invasion. Sagittal sinus around the
mass is patent.
Compression from a Meningioma
Teaching Point:
If a mass compresses the
venous sinus, a venogram
should be performed to
evaluate for thrombosis and
invasion.
MRV MIP and source data: Mild irregularity and narrowing of the superior sagittal
sinus at the region of the meningioma due to compression. No significant thrombosis
or occlusion.
Compression from a Meningioma
T1WC+: Homogenously enhancing mass in the
superior vermian cistern with a broad based
dural tail extending along the tentorium.
MRV: Narrowing of the posterior two
thirds of the straight sinus due to mass
effect from the meningioma.
Occlusion from a Meningioma
62 year old female with
headache and papilledema.
T1WC+: Homogenously enhancing extra-axial mass in the posterior left cerebellopontine angle cistern.
The mass closely abuts the left transverse sinus as it turns into the sigmoid sinus.
Occlusion from a Meningioma
MRV from the
same patient.
Occlusion of the left transverse
sinus at the level of the mass.
Flow is seen in the left IJ vein at
the skull base.
Source data better depicts flow in
the left sigmoid sinus and IJ vein
Thrombosis from a Schwannoma
Bilateral schwannomas
Filling defect in the
right transverse
sinus due to
thrombus
MRV shows thrombus in the distal right
transverse sinus and narrowing in bilateral
transverse sinuses due to mass effect. The
right internal jugular vein is diminutive.
Occlusion from Squamous Cell
Carcinoma
70 year old male with chronic right
mastoiditis and subperiosteal abscess.
TW1C+: Enhancing right
mastoid mass.
T2W: Central T2
hypointense signal in the
right transverse sinus.
TOF MRV: Distal right transverse,
sigmoid sinus, and IJ vein are not
seen, consistent with occlusion.
Thrombosis from RCC Metastasis
Nonenhanced CT: Soft tissue mass with osseous destruction of right
occipital condyle, hypoglossal canal, and jugular foramen.
T1WC+ with fat saturation:
Enhancing mass in the jugular
foramen with occlusion of the
jugular foramen.
Thrombosis from RCC Metastasis
T1WC+: Filling defect in the
right transverse sinus,
consistent with clot.
T2W: Enlarged right IJ vein with
abnormal signal, consistent with
thrombosis.
TOF MRV: Filling defect in the right
transverse sinus, consistent with clot.
Long segment of absent signal in right
sigmoid & IJ vein, consistent with
thrombosis and occlusion.
Occlusion from Epidermoid
•
CT: Lobulated extra-axial mass in the left
occipital region with serpeginous ring and arc
like calcifications within the mass. The mass
erodes the occipital bone and posterior aspect
of the temporal bone.
•
Axial ADC map does not show low ADC signal.
•
There are areas of high T1 and low GRE signal,
consistent with hemorrhagic blood products.
•
The majority of the mass is T2 hyperintense.
•
The mass abuts the transverse and sigmoid.
Occlusion from Epidermoid
MRV from the
same patient.
TOF
Phase Contrast
Teaching Points:
• The differential diagnosis of an
extra-axial mass with ring and
arc like calcifications include
hemangiopericytoma,
chondrosarcoma, chordoma,
and aggressive meningioma.
•
MRV shows occlusion of the left transverse and sigmoid sinuses.
This is an atypical appearance
of an epidermoid, which did
not demonstrate restricted
diffusion.
Management of Cerebral Venous
Thrombosis
Endovascular therapy
may be considered in
patients with absolute
contraindications for
anticoagulation
therapy or failure of
initial therapeutic
doses of anticoagulant
therapy.
Gustavo Saposnik et al. Stroke. 2011;42:1158-1192
Summary
• Familiarity with common pitfalls of MRV will assist in
the accurate interpretation and diagnosis of the
intracranial venous system.
• Correlating imaging findings on different MRV
sequences and reviewing the source data can avoid
diagnostic pitfalls associated with all imaging
techniques.
• Knowledge of the typical and subtle imaging features
of common pathologies of the cerebral venous sinuses
will lead to prompt diagnosis and treatment, which can
improve prognosis.
References
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Suppl):S64-75
Ayanzen RH, Bird CR, Keller PJ et al. Cerebral MR venography: normal anatomy and
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Glockner JF, Lee CU. Magnetic Resonance Venography. Appl Radiol. 2010:39:36-42
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management of cerebral venous thrombosis: a statement for healthcare
professionals from the American Heart Association/American Stroke Association.
Stroke. 2011;42(4):1158-92
Contact Information
Jennifer Trinh, MD
Department of Radiology
Santa Clara Valley Medical Center
751 S. Bascom Ave.
San Jose, CA 95125
[email protected]