DVT Protocols

• Leg swelling
• Trauma patient
• Post-op from orthopedic surgery
• Non-diagnostic ultrasound for DVT
• Suspect pelvic DVT (e.g. during pregnancy)
• Evaluate proximal extent of known DVT
• Evaluate for free-floating thrombus
• Pre-op for venous reconstructive surgery

• Valium (5-10 mg po) or Xanax (1-2 mg po) if patient is claustrophobic
• Place respiratory bellows
• Keep legs warm with lots of blankets to maximize flow to legs; consider elevating ankles to enhance venous return

Coil: Body coil is best because of its large uniform field-of-view. If using the torso array, consider rotating 90 degrees for greater S/I coverage.

Patient Positioning: Supine, feet first, feet taped together to remind patient to hold still. Consider velcro strips to assist un-cooperative patients in holding still.

Landmark: Public Symphysis

Use axial 2D TOF to image from above the iliac crest down to below the knee. Do this in at least two stations to avoid acquiring poor quality images at the inferior and superior extend of the image volume. Any region that has an intraluminal filling defect should be further imaged with 2D Phase Contrast MRA with superior-to-inferior flow encoding. This helps determine if a filling defect on TOF is real or simply a flow artifact. To distinguish between acute and chronic venous thrombosis, axial T2 and Axial T1 fat sat post gadolinium are helpful. Acute Thrombosis stimulates a peri-venous inflammatory response that is T2 bright and enhances with gadolinium contrast. Finally if the saphenous vein is being considered for a venous bypass, it may be necessary to verify saphenous vein patency into the CFV. This requires an additional TOF sequence using 3mm contiguous slices (no gap) from the level of the lesser trochantor to above the top of the pubic symphysis.

• Measure from Landmark to just above the iliac crest. Set the scan location beginning at a superior offset of at least this distance to ensure including distal IVC.
• Use thin slices (3 mm) with a long TR (40-50 msec) to maximize time-of flight effect .
• Use large gaps between slices (5-7 mm) to avoid taking an excessively long time.
• Do not use any saturation pulses. It is important to see the arteries as a marker to help find the veins.

• Measure from landmark (pubic symphysis) down to 50mm below patella. Use this for the most inferior distance to ensure coverage of the entire popliteal artery.
• No sat pulses.
• Thin slices (3mm), long TR (40-50 msec) to maximize TOF effect, use large gaps (5-7 mm) in between slices to it does not take forever.

Series 3: 2D phase contrast (optional)

• This sequence helps for evaluating areas of suspected DVT seen on series 1 or 2.
• Use 5 mm slices with no gap to ensure complete coverage of every mm of vein in these suspicious regions.
• Adjust Venc: Pelvis 40cm/sec
                       Thigh 30cm/sec
                       Calf 20cm/sec

Additional Parameters:

• Vascular Screen
• Flow Recon Type: Phase Diff.
• Velocity Encoding 40
• Acq. Flow Direction S/I
• Collapse on
• Flow Quantitation off
• Additional Images Mag

• Series 1 & 2: 12 on 1 format with images doubled up to put 24 slices per sheet of film
• Adjust window/lead so background is dark and veins are bright
• Series 3:
  • Try to fit on 1 sheet of film
  • Double-up images with magnitude image on top, phase image on bottom
  • Use narrow window for magnitude image (<500)
  • Use very wide window for phase image (>2000) so background is grey while arteries and veins are black and white.

Billing:

ICD9 Codes:

Sample normal dictation:

The patient was imaged with axial 2D time-of-flight with 5 mm gaps from the distal IVC down to below the knee joint. Areas of intraluminal filling defect were further evaluated using 2D PC to discriminate between acute thrombus, sennechiae and flow artifact.

The distal IVC, iliac veins, common femoral, profunda femoral and femoral veins and popliteal vein are all widely patent bilaterally with no intraluminal filling defects.

Impression: No deep venous thrombosis.