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Quality Assurance in Dural
Venous Sinus Imaging –
Comparison of MR Venography
Techniques
Dr. Jonathan Kim, Dr. Rafeeque Bhadelia, Dr. David Hackney, Dr.
Rafael Rojas
Control #: 1700
eEdE#: eEdE-39
Disclosures
• No financial disclosures to report.
Outline
• General diagnostic pitfalls of MR imaging of dural venous sinus
thrombosis
• Acquisition factors and artifact profiles
– Time-of flight
– Phase Contrast
– Contrast enhanced 3D MP-RAGE
Dural Venous Sinus Thrombosis
(DVST)
• Relatively rare with an estimated annual incidence of 2-7 cases
per million
• Clinical presentation is nonspecific and diagnosis is highly
reliant on imagine
• Gold standard for diagnosis is cerebral venous angiography, an
invasive technique
• Modern diagnostic technique has been largely supplanted with
MR angiographic studies
• As DVST is potentially fatal, prompt diagnosis is key
1. Leach et al.
General Diagnostic Pitfalls
Normal anatomic variants: Right, left and codominant transverse
sinuses. Sinus asymmetry should not be confused for occlusion.
2. Ayanzen et al.
General Diagnostic Pitfalls
• Flow gaps may be observed in the nondominant sinus and may
be indistinguishable from thrombus on flow dependent
techniques
2. Ayanzen et al.
General Diagnostic Pitfalls
• Normal structures including pacchonian granulations and
chordae willisii demonstrate well defined filling defects
• Seen in at least 90% of patients
7. Leach et al.
General Diagnostic Pitfalls
• Venographic phase of a cerebral angiogram demonstrates
preserved flow where MRV demonstrated a flow gap
2. Ayanzen et al.
Time-of Flight
• 2D-TOF MR venography is the most commonly used technique
for evaluation of DVST
• Gradient echo sequence with imaging differential created by
difference between saturated and non-saturated blood
– Non-saturated blood entering the imaging slice creates inflow contrast
– Arterial flow is nulled with a pre-saturation pulse adjacent to
the slab of interest
• High sensitivity for slow-flow
• Most sensitive to flow perpendicular to the image acquisition
plane (important technical factor)
7. Leach et al.
Time-of Flight
• 2D-TOF imaging is sensitive to
slow flow, but there is a lower
limit (roughly 3 cm/s)
– Below this, flow gaps
become apparent
• This can be minimized by
decreasing slice thickness
– Signal loss is due to blood
pool spin loss before pulse
repetition time, so imaging a
smaller slice decreases the
probability of signal loss
3. Rollins et al.
Time-of Flight
• Loss of signal within the
superior sagittal sinus
secondary to in-plane flow
• 2D-TOF imaging is acquisition
plane dependent thus the
ideal imaging plane is
perpendicular to flow direction
• Acquisition is generally in the
coronal plane, but this places
portions of the sagittal and
transverse sinuses in-plane
and loss of signal is possible
3. Rollins et al.
Time-of Flight
• 2D-TOF acquired in the axial plane demonstrates in-plane
signal loss in areas of the straight and transverse sinuses as
opposed to the previous example of coronal acquisition
• Flow gaps demonstrated in at least 31% of TOF studies
7. Leach et al.
Time-of Flight
• T1 shine through from subacute thrombus may produce
intravascular signal that can be confused for preservation of flow
7. Leach et al.
Phase Contrast
• Phase contrast images are sensitive to flow
• Moving protons in a region of interest generate phase shift
artifacts in the plane of the magnetization gradient
• Degree of phase shift is proportional to the velocity which is then
used to generate angiographic images
Phase Contrast
• Acquisition of phase contrast venography images depends on a
priori selection of velocity encoding (VENC) values
• VENC serves as a center point to the estimated velocity of blood
flow to be imaged
• If VENC is incorrectly selected, flows that are much higher or
lower may not be seen
• VENC should be roughly 25% than expected Vmax for ideal
imaging
• Since flow is not known prior to imaging, multiple acquisitions
with varying VENC may be required causing increased imaging
time
4. Lotz et al.
Phase Contrast
• 3D-PC images with VENC values of 15 and 40 cm/s,
respectively demonstrate areas of signal loss when flow is too
far outside the selected VENC range
5. Fera et al.
Phase Contrast
• Phase contrast images are not dependent on imaging plane and
demonstrate excellent image quality with proper VENC selection
3D CE MP-RAGE
• Post-gadolinium 3D magnetization prepared rapid gradient-echo
sequences depend on the T1 shortening effect of gadolinium to
provide enhancement of intravascular structures
• As intravascular signal depends on contrast concentration, CE
MP-RAGE is not susceptible to the artifact profile of TOF or PC
such as vessel angle compared to the acquisition plane, nor is it
related to flow velocities
• As gadolinium is required, some patient populations are not
amenable to this technique, such as pregnant patients
6. Liang et al.
3D CE MP-RAGE
• Flow gap seen in the left transverse sinus on 2D-TOF whereas
CE MP-RAGE clearly demonstrates intravascular enhancement
of a hypoplastic vessel
• Patent venous sinus is confirmed on venous phase DSA
6. Liang et al.
3D CE MP-RAGE
• MP-RAGE is also useful for direct visualization of thrombus in
conjuction with other sequences
• Apparent flow gap in 2D-TOF image is indeterminate, but clearly
demonstrates thrombosis on MP-RAGE
6. Liang et al.
Summary
• DVST is a rare entity, but diagnostically important as early
treatment is related to eventual outcomes
• TOF and PC are non-contrast, flow related techniques with
acquisition parameters and artifact profiles that are important to
keep in mind during interpretation
• 3D CE MP-RAGE is not flow dependent, and is potentially
superior to TOF and PC, but requires gadolinium contrast
References
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Leach, James L., et al. "Imaging of Cerebral Venous Thrombosis: Current Techniques, Spectrum of
Findings, and Diagnostic Pitfalls 1." Radiographics 26.suppl_1 (2006): S19-S41.
Ayanzen, R. H., et al. "Cerebral MR venography: normal anatomy and potential diagnostic
pitfalls." American Journal of Neuroradiology 21.1 (2000): 74-78.
Rollins, Nancy, et al. "Cerebral MR Venography in Children: Comparison of 2D Time-of-Flight and
Gadolinium-enhanced 3D Gradient-Echo Techniques 1."Radiology 235.3 (2005): 1011-1017.
Lotz, Joachim, et al. "Cardiovascular Flow Measurement with Phase-Contrast MR Imaging: Basic Facts
and Implementation 1." Radiographics 22.3 (2002): 651-671.
Fera, Francesco, et al. "Comparison of different MR venography techniques for detecting transverse
sinus stenosis in idiopathic intracranial hypertension."Journal of neurology 252.9 (2005): 1021-1025.
Liang, Luxia, et al. "Evaluation of the intracranial dural sinuses with a 3D contrast-enhanced MP-RAGE
sequence: prospective comparison with 2D-TOF MR venography and digital subtraction
angiography." American journal of neuroradiology 22.3 (2001): 481-492.
Leach, James L., et al. "Imaging of Cerebral Venous Thrombosis: Current Techniques, Spectrum of
Findings, and Diagnostic Pitfalls 1." Radiographics26.suppl_1 (2006): S19-S41.