Intima-media thickness (IMT)

David Goldemund M.D.
Updated on 29/02/2024, published on 26/03/2021

  • the measurement of carotid intima-media thickness (IMT, CIMT) can quantify atherosclerosis burden in asymptomatic patients, which may require a more aggressive approach to managing vascular risk factors
  • decades of silent arterial wall alterations precede atherosclerotic disease with clinically evident cardiovascular events
  • the first detectable morphological abnormalities (enlargement of intima-media) can be visualized using B-mode imaging
  • the intima-media extends from the luminal edge of the artery to the boundary between the media and the adventitia
How to measure IMT?
  • the standard measurement is performed in B-mode on the far wall of the common carotid artery (CCA), 10 mm proximal to the bifurcation
    • use high-resolution images and adjust depth of focus and gain settings to obtain optimal image quality
    • employ linear ultrasound transducers at frequencies above 7 MHz
    • optimize the insonation angle (90° to the vessel wall)
    • values obtained from different sites (such as distal ICA, bulb) should be documented separately
    • values from the near wall are dependent on gain settings and are thus less reliable
  • measure the distance between the 2 parallel echogenic lines
    • the first line represents the lumen-intima interface
    • the seond line represents the media-adventitia interface
  • obtain at least five measurements on each side and calculate the average value (“average IMT”); specialized software may be helpful  Automated IMT measurement (GE LOGIQ) [Baldassare, 2000]
    • automated systems can rapidly provide the mean maximal value of 150 measurements performed over a 10 mm segment of the CCA
  • perform IMT measurements in a region free of atherosclerotic plaque, which is defined as:
    • lesion ≥1.5 mm
    • structure encroaching into the arterial lumen by at least 0.5 mm or 50% of the surrounding IMT value
  • interadventitial and lumen diameter must also be obtained, as IMT correlates with arterial diameter
  • echogenicity, especially of the media, may be increased in the presence of fatty infiltration and thickening
Carotid intima-media thickness (CIMT)
What is normal IMT?
  • IMT > 75-95th percentile for age and sex is considered abnormal
  • some authors suggest simple cut-off values:
    • IMT < 0.8 mm – value associated with normal healthy individuals
    • IMT ≥ 1 mm – value associated with atherosclerosis and a significantly increased risk of cardiovascular disease (CVD) in any age group
Intima-media thickness (IMT) on ultrasound imaging
Women (95. percentile)
Men (95. percentile)
45 y
55 y
65 y
45 y 55 y
65 y
0.91 1.04
1 1.3 percentile  [Howard, 1993]

P25 P50
men <30 0.39 0.43 0.48
men 31-40  0.42 0.46 0.50
men 41-50 0.46 0.50 0.57
men >50  0.46 0.52 0.62
women <30 0.39 0.40 0.43
women 31-40 0.42 0.45 0.49
women 41-50 0.44 0.48 0.53
women >50 0.50 0.54 0.59

Prognostic value of IMT measurement

  • not only atherosclerotic plaques but also IMT can quantify atherosclerosis burden in asymptomatic patients
  • IMT should be assessed in each extracranial ultrasound examination
    • increased IMT represents the first stage of atherosclerosis and, if left untreated, is followed by plaque formation
    • clinical and epidemiological studies have shown an association between IMT and coronary artery disease (CAD), stroke, and peripheral vascular disease (PAD) (ROTTERDAM, ACAPS trials ) [Lorenz, 2007]
    • thickening of IMT correlates with the presence of traditional vascular risk factors (high BMI, hypertension, hypercholesterolemia, diabetes, smoking)
    • some authors recommend including both IMT and the presence of atherosclerotic plaquess among the classic vascular risk factors [Chambless, 2010]
    • some publications question significance of IMT in predicting cardiovascular events [Costanzo, 2010] [Ruijter, 2012]
  • detection of subclinical atherosclerosis is important in patients with borderline risk and multiple risk factors, as it shifts the patient into the high-risk category (SCORE ≥ 5%) with all therapeutic consequences
  • pharmacological studies have shown a reduction in the rate of progression of IMT with hypolipidemic therapy and antihypertensive drugs (ACAPS, METEOR)
  • on the other hand, a meta-analysis of 41 randomized trials showed regression of cardiovascular events with hypolipidemic drugs but did not show a relationship between a decrease in CV events and a regression of IMT [Costanzo, 2010]
  • an enlarged arterial wall can also be found in non-atherosclerotic diseases (e.g., Takayasu arteritis)

You cannot copy content of this page

Send this to a friend
you may find this topic useful:

Intima-media thickness (IMT)