CT cerebral venography (technique)
CT cerebral venography (also known as a CTV head) is a contrast enhanced examination with an acquisition delay providing an accurate detailed depiction of the cerebral venous system.
NB: This article is intended to outline some general principles of protocol design. The specifics will vary depending on CT hardware and software, radiologists' and referrers' preference, institutional protocols, patient factors (e.g. allergy) and time constraints.
Indications
Rapid diagnosis of cerebral venous thrombosis.
Contraindications
IV iodinated contrast contraindications, such as chronic renal failure
Technique
- patient position
- supine with their arms by their side
- scout
- CT to the vertex
- scan extent
- CT to the vertex
- scan direction
- caudocranial
- contrast injection considerations
- injection
- 75-100 ml of non-iconic iodinated contrast
- injection
- scan delay
- 45 seconds (see practical points)
- respiration phase
- suspended
Data acquisition and analysis
- images are analyzed on a dedicated workstation
- proper evaluation of the dural sinuses indicates proper inspection of the axial thin-section contrast-enhanced source images of a helical CT scan
- two-dimensional (2D) & three-dimensional (3D) multiplanar images, as well as rendering techniques such as maximum intensity projection (MIP), surface shaded displays (SSD) and volume rendering (VR) in a sagittal, coronal, and oblique planes
- an essential step in CT venography is the removal of bone from the images, by graded subtraction
Findings
Venous sinus abnormalities
- dural venous sinus thrombosis
- thrombosis recanalization, the sinus shows an irregular appearance with multiple intrasinus channels and dural collateral vessels
- sinus stenosis or occlusion secondary to tumor invasion (e.g. meningioma)
- vascular malformations (e.g. AVM, dural arteriovenous fistula or developmental venous anomaly)
- idiopathic intracranial hypertension: bilateral stenoses of the transverse sinuses, without definitive evidence of current or prior thrombosis
Parenchymal abnormalities
- cerebral parenchymal abnormalities such as hemorrhagic infarction
Variant anatomy
- sinus hypoplasia and aplasia
- arachnoid granulations
- sinus duplication or fenestration
- variant anatomy of the sinuses (e.g. occipital sinus or persistent falcine sinus)
Practical points
Caution must be taken to achieve a well-timed acquisition in CT cerebral venography, particularly in cases of intracranial hypertension which can cause delayed filling of the venous sinus. A premature acquisition may create a false impression of thrombosis, which is simply due to contrast not yet reaching the venous sinuses - if the cerebral veins are not opacified on a CT cerebral venogram, premature acquisition should be suspected.
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