What is MRV (Magnetic Resonance Venography)?

Magnetic Resonance Venography (MRV): Definition and Clinical Applications

Magnetic Resonance Venography (MRV) is a specialized non-invasive imaging technique that generates detailed images of veins using magnetic resonance technology, allowing for visualization of venous structures and detection of pathologies such as thrombosis, stenosis, and compression without requiring ionizing radiation. 1

Technical Aspects of MRV

• MRV can be performed using both contrast and non-contrast techniques:

  • Non-contrast techniques rely on intrinsic properties of flowing blood with sensitivity of 91.5-93% and specificity of 94.8-96% for detecting deep vein thrombosis (DVT) 2
  • Contrast-enhanced techniques use intravenous gadolinium-based agents to produce bright signal in patent vessels 1

• Common MRV techniques include:

  • Time-of-flight (TOF) MRV - most commonly used 2D technique that is highly sensitive to slow flow 1
  • Contrast-enhanced MRV - provides improved visualization of venous structures 1
  • Phase-contrast MRI - less frequently used due to difficulty in defining velocity encoding parameters 1

• Image acquisition typically requires a 90-120 second delay after contrast injection to allow the bolus to enter the venous or equilibrium phase 1

Clinical Applications

• MRV is particularly valuable for evaluating central venous structures that cannot be directly imaged by ultrasound 1

• Key applications include:

  • Detection of deep vein thrombosis in upper and lower extremities 1, 3
  • Evaluation of cerebral venous thrombosis 1
  • Assessment of chronic venous disease 1
  • Identification of venous anatomical variants important for treatment planning 1
  • Visualization of extrinsic venous compression from masses or other structures 2

• MRV can detect specific venous pathologies:

  • Thrombus appears as filling defects in contrast-enhanced studies 1
  • Venous stenosis, occlusion, and atresia 1
  • Webs, trabeculations, and vein wall thickening 1
  • Collateral venous pathways 1

Advantages of MRV

• Does not use ionizing radiation, making it safer for repeated studies 4

• Provides high-resolution images of soft tissues surrounding vessels, helping identify:

  • Mimics of DVT 2
  • Potential sources of extrinsic venous compression 2
  • Signs of soft-tissue inflammation around veins 1

• Can distinguish between acute and chronic DVT in many cases 2, 5

• High diagnostic accuracy with sensitivity of 100% and specificity of 96% when compared to contrast venography in some studies 3

Limitations and Considerations

• Not routinely accessible for DVT diagnosis in most centers 2

• More expensive and time-consuming than ultrasound, which remains the first-line imaging modality for suspected DVT 2, 6

• Potential risks associated with gadolinium-based contrast agents, particularly in patients with renal failure 1

• Technical challenges including:

  • Breathing artifacts may impair imaging quality 1
  • Flow artifacts can affect image interpretation 1
  • Variability in techniques between institutions 2

Current Diagnostic Algorithm

• Ultrasound duplex Doppler is recommended as the initial imaging examination for suspected DVT due to its high sensitivity, non-invasive nature, and widespread availability 2, 6

• MRV should be considered when:

  • Ultrasound is inadequate or non-diagnostic 2
  • Evaluation of central venous structures is needed 1
  • Assessment of pelvic or abdominal vein thrombosis is required 2

• Catheter venography remains the reference standard but is rarely used as the first imaging modality due to its invasive nature 1

Special Considerations

• In cerebral venous thrombosis, 2D TOF is the most commonly used MRV technique due to its excellent sensitivity to slow flow 1

• For chronic venous disease, gadolinium-enhanced MRV with contrast is preferred due to high intravascular enhancement and acquisition of isotropic voxels with high spatial resolution 1

• In patients with suspected upper extremity DVT, MRV is particularly useful for evaluating central veins that cannot be adequately assessed with ultrasound 1