Intima-media thickness (IMT) is an indirect sonographic assessment of the degree of atheromatous vascular disease of end organs. The thickness of the media and the intima of the vessels changes following many conditions and it can be easily and reliably assessed with ultrasound on B mode in the common carotid arteries (CCA) 1,2.
Measurement
There are different protocols for assessment of CCA-IMT. Foci of atheromatous plaques need to be avoided when measuring IMT. The measurement is made between the two bright lines made by blood-intima interface and media-adventitia junction as the far and near-wall respectively 4:
- the patient should be kept on supine position and head turned away from the side of the examination
- sagittal imaging of the CCA has to be used and take at least five measurements on each side to obtain an average value ("average IMT")
- measure on the posterior wall of the common carotids on the right and on the left, 1 cm from the carotid bifurcation
Interpretation
The average IMT value is calculated for each common carotid artery and >1 mm is taken as abnormal 4.
The CCA-IMT has a linear relationship with systemic atherosclerosis burden 1,2. It predicts the risk of developing future cerebrovascular or cardiac thrombotic and can be used as a screening tool 2. The CCA-IMT in patients with metabolic syndrome is significantly increased with or without abdominal obesity 3.
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