1. 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

2. Disclosures
No financial disclosures to report.

3. 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

4. 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.

5. General Diagnostic Pitfalls
Normal anatomic variants: Right, left and codominant transverse sinuses. Sinus asymmetry should not be confused for occlusion.
2. Ayanzen et al.

6. 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.

7. 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.

8. General Diagnostic Pitfalls
Venographic phase of a cerebral angiogram demonstrates preserved flow where MRV demonstrated a flow gap
2. Ayanzen et al.

9. 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 in-flow 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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

15. 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.

16. 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.

17. Phase Contrast
Phase contrast images are not dependent on imaging plane and demonstrate excellent image quality with proper VENC selection

18. 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.

19. 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.

20. 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.

21. 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

22. References
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):
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):
Lotz, Joachim, et al. "Cardiovascular Flow Measurement with Phase-Contrast MR Imaging: Basic Facts and Implementation 1." Radiographics 22.3 (2002):
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):
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):
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.