Other Imaging Modalities

Other less frequent imaging modalities include:

Impedance plethysmography

• Impedance plethysmography  is a non-invasive test that measures small changes in electrical resistance of the calf. These measurements reflect blood volume changes, and can indirectly indicate the presence or absence of venous thrombosis.
• Insensitive for non-occluding thrombus, calf thrombus, or thrombus above the inguinal ligament

MRI

• Approaching venography for sensitivity and specificity
• Highly sensitive for calf thrombus, also for thrombus above the inguinal ligament when CT not practical
• Particular benefit in pregnancy when Doppler flow characteristics change with the gravid uterus
• Limited availability of scanners

CT

• Limited trials report similar results to ultrasonography
• Effective in diagnosis of ileofemoral and more proximal thrombus
• Problems arise with contrast reactions, radiation exposure and presence of metal implants

Venography

• Previously the gold standard, this has now been replaced with non-invasive and less harmful techniques such as ultrasound.