NEUROSONOLOGY

Intima-media thickness (IMT)

Created 01.08.2019 , last update 05.11.2021

  • carotid intima-media thickness (IMT) measurement can quantify atherosclerosis burden in asymptomatic patients, which may need a more aggressive approach to managing the vascular risk factors
  • the standard measurement is performed in B-mode on the far wall of CCA, 10 mm proximal from the bifurcation
    • use high-resolution images
    • optimize the angle of insonation (90° to the vessel wall)
  • distance of 2 echogenic lines is measured
    • the 1st line is the lumen-intima interface
    • the 2nd line is the media-adventitia interface
  • get at least five measurements on each side and get an average value (“average IMT”); specialized software can be helpful  Automated IMT measurement (GE LOGIQ) [Baldassare, 2000]
  • avoid atherosclerotic plaques when measuring IMT (lesions > 1.5 mm are already evaluated as plaque)
  • echogenicity, especially of the media, can increase in the presence of fatty infiltration and thickening
  • IMT > 95th. percentile for age and sex is taken as abnormal (usually IMT >1 mm is abnormal)
Intima-media thickness (ultrasound image)
Intima-media thickness (IMT) on ultrasound imaging
Female (P95)
Male (P95)
45 y
55 y
65 y
45 y 55 y
65 y
0.73
0.91 1.04
0.89
1 1.3

95.th percentile  [Howard, 1993]

Age
P25 P50
P75
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 IMT as well can quantify atherosclerosis burden in asymptomatic patients
  • IMT should be assessed in each extracranial ultrasound exam
    • an increase in the intima-media thickness is the first stage of atherosclerosis, and if untreated, it is followed by plaque formation
    • clinical and epidemiologic studies showed an association of IMT with coronary artery disease (CAD), stroke, and peripheral vascular disease (PAD) (ROTTERDAM, ACAPS trials ) [Lorenz, 2007]
    • thickening of IMT correlates with the occurrence of traditional vascular risk factors (BMI, hypertension, hypercholesterolemia, diabetes, smoking)
    • some authors recommend including IMT and the AS plaques presence among the classic vascular risk factors [Chambless, 2010]
    • some publications question the importance of IMT in the CV events predictions [Costanzo, 2010] [Ruijter, 2012]
  • detection of subclinical atherosclerosis is important in patients with borderline risk and multiple risk factors, as it moves the patient to the high-risk category (≥ 5% by SCORE) with all therapeutic consequences
  • pharmacological studies have shown a reduction in the rate of progression of IMT on hypolipidemic therapy and antihypertensives (ACAPS, METEOR)
    • rosuvastatin did not induce disease regression
  • on the other hand, a meta-analysis of 41 randomized trials showed regression of cardiovascular events on hypolipidemic drugs but did not show a relationship between a decrease in CV events and regression of the IMT [Costanzo, 2010]
  • an increase in IMT can also be found in non-atherosclerotic diseases (e.g., Takayasu arteritis)
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