Quantification and assessment of carotid artery lesions: Degree of stenosis and plaque volume

Abstract

Various methods were developed for the quantification of the degree of stenosis: B-mode imaging, CW Doppler with spectral analysis, PW-duplex, and color-flow imaging. The degree of stenosis can be evaluated using transverse views of the carotid in conventional B-mode imaging. The diameters of the residual lumen (Ds) and the external diameter (De) of the artery at the same level are measured and the degree of stenosis (in area) is calculated. Two different Doppler methods have been designed and validated for the quantification of the stenosis degree. The first one is based on the determination of the maximal velocity inside the stenosis and requires the use of a duplex device. The second one, based on the quantification of the hemodynamic disturbances at the outlet of the stenosis, can be used either with a duplex system or with a continuous-wave Doppler system (pencil probe). The color display mode facilitates the determination of the residual lumen and therefore contributes to making the B-mode method more accurate. Moreover, it provides a visualization of the blood flow which avoids most of the misinterpretations of B-mode or Doppler data. Several classification systems based on subjective or semi-quantitative criteria (morphological or hemodynamic) were used to identify different grades of stenosis (< 40%, 40% to 60%, 60% to 90%, etc.) These classifications provide an evaluation of the degree of stenosis accurate enough to discuss the possibility of performing an endarterectomy on a symptomatic patient. When the surgical treatment seems to be inappropriate, the patient is treated medically; the follow-up of the lesion (ie, every 6 months) requires a more precise evaluation of the plaque changes than does stenosis classification. Several parameters have been designed and validated for the quantification of the degree of stenosis by ultrasound. These parameters, whether measured with the B-mode and color image or with the Doppler spectrum, allow quantification of the stenosis degree in percentage of lumen reduction with a precision of approximately +/- 10%. Such a quantitative assessment of carotid lesions for a long period of time may be very helpful in evaluating the beneficial effects of medical treatment or in detecting any significant increase of the stenosis that could lead to surgical treatment. A new method for the plaque volume assessment has been recently validated. The plaque volume index expressed in mm3 is calculated from longitudinal and transversal B mode views of the bifurcation.

Clinically underdetected asymptomatic and symptomatic carotid stenosis as a late complication of radiotherapy in Chinese nasopharyngeal carcinoma patients

“…21 Doppler ultrasonography of the neck is a noninvasive, rapid, and easily available imaging modality for assessing carotid stenosis and evaluating risk and selecting patients for further investigation or treatment. [22][23][24] The carotid intimamedia thickness and carotid plaques can be used as markers for increased risk of stroke. 25,26 The progression of internal carotid artery stenosis was also found to correlate with ischemic neurologic events but not baseline stenosis, and hence serial duplex scans are justified for following carotid stenosis.…”

Impact of Infectious Burden on Extent and Long-Term Prognosis of Atherosclerosis

“…In accordance with previous reports, peak velocities of Ͼ1.4 m/s were assumed to indicate a Ͼ50% diameter lumen stenosis. 17 Peripheral vascular status was investigated by Doppler flow velocity study with the use of a 4-MHz transducer for the femoral and popliteal arteries and an 8-MHz transducer for the foot arteries. Clinically manifest peripheral artery disease was diagnosed after a previous peripheral revascularization or if an ankle-arm index (systolic blood pressure ankle/arm) of Ͻ0.9 could be detected in at least one pedal artery with pathological monophasic Doppler waves.…”

Impact of Infectious Burden on Progression of Carotid Atherosclerosis

“…In accordance with previous reports, a peak systolic velocity of Ͼ1.4 m/s and a ratio of peak velocity of the common carotid artery to peak velocity of the internal carotid artery of Ն2 were assumed to indicate Ն60% diameter lumen stenosis. 14,20 The development of a new Ն60% stenosis or an increase in a previous stenosis (increase in peak velocity ratio of at least 0.5) was defined as progression of stenosis (new stenosis, nϭ32; increase in previous stenosis, nϭ26; total progression of stenosis, nϭ58; 13.5%). Follow-up IMT and progression of stenosis were assessed in all 427 patients with completed follow-up.…”