[Quantifying stenosis of the internal carotid artery: which ultrasound criteria are relevant?]

[Color duplex sonography of extracranial brain-supplying arteries]

Ultrasound examination of extracranial blood-supplying arteries allows the simultaneous acquisition of morphologic and hemodynamic information with high spatial and temporal resolution. For detection and quantification of stenoses in the carotid and vertebral arteries, an intrastenotic peak systolic velocity of more than 120 cm/s is the threshold value for a diameter reduction of >50%. In addition there are further direct and indirect stenosis parameters (intrastenotic and poststenotic circulation disturbance, increased pulsatility in the prestenotic common carotid artery, intracranial or extracranial collateral pathways) which together with diameter and area reduction in the B-scan, lead to a high reliability of color duplex sonography for stenoses of the internal carotid artery (ICA). Sonographic and patho-anatomic comparative studies have shown a high agreement (r >0.9) by using a battery of several ultrasound criteria. Following stenting of the ICA the blood flow velocity in the stent is generally increased so that a > or =70% in-stent restenosis is present in case of a peak systolic velocity of 300-450 cm/s. For the description of arteriosclerotic plaques in the B-scan, ultrasound terminology but not histological terms should be used to describe the internal, surface and motion structure of plaques as well as the sonic shadow formation.

[Ultrasound in vascular surgery]

Diagnosing vascular diseases by ultrasound is of major interest to vascular surgeons and now regarded as the primary noninvasive technique. This paper presents developments in four different fields: stenoses of the carotid arteries, peripheral artery occlusive diseases (PAOD) including surveillance programs, diseases of the veins, and abdominal aortic aneurysm. Calculating the extent of a carotid artery stenosis is now accurate, but plaque imaging remains complex. Examination by ultrasound should precede any invasive techniques in PAOD. Duplex surveillance on a routine basis is no longer recommended after infrainguinal bypass. In future vascular diseases will be diagnosed primarily by ultrasound. Diagnosis of abdominal aneurysm is now absolutely reliable, whereas planning and follow-up of endoluminal techniques are quite restricted.

Color Doppler, power Doppler and B-flow ultrasound in the assessment of ICA stenosis: Comparison with 64-MD-CT angiography

The purpose of this study is to investigate the diagnostic potential of color-coded Doppler sonography (CCDS), power-Doppler (PD) and B-flow ultrasound in assessing the degree of extracranial internal carotid artery (ICA) stenosis in comparison to CT-angiography (MD-CTA). Thirty-two consecutive patients referred for CTA with 41 ICA-stenoses were included in this prospective study. MD-CTA was performed using a 64 row scanner with a CTDIvol of 13.1 mGy/cm. In CTA, CCDS, PD and B-flow, the degree of stenosis was evaluated by the minimal intrastenotic diameter in comparison to the poststenotic diameter. Two radiologists performed a quantitative evaluation of the stenoses in consensus blinded to the results of ultrasound. These were correlated to CTA, CCDS, PD and B-flow, intraoperative findings and clinical follow-up. Grading of the stenoses in B-flow ultrasound outperformed the other techniques in terms of accuracy with a correlation coefficient to CTA of 0.88, while PD and CCDS measurements yield coefficients of 0.74 and 0.70. Bland-Altman analysis additionally shows a very little bias of the three US methods between 0.5 and 3.2 %. There is excellent correlation (coefficient 0.88, CI 0.77-0.93) with 64-MD-CTA and B-flow ultrasound in terms of accuracy for intrastenotic and poststenotic diameter. Duplex sonography is useful for screening purposes.

Diagnostics and characterisation of preocclusive stenoses and occlusions of the internal carotid artery with B-flow

The purpose was to evaluate whether B-flow can improve the ultrasonographic diagnosis of preocclusive stenosis and occlusion of the internal carotid artery (ICA) compared with colour-coded Doppler and power Doppler. Ninety patients with occlusions or preocclusive stenoses of the ICA suspected by Doppler sonography were examined with B-flow in comparison with colour-coded Doppler sonography (CCDS), power Doppler (PD) and intra-arterial digital subtraction angiography (DSA). Intrastenotic flow detection and lengths of stenoses were the main criteria. Ulcerated plaques found by surgery in 42/90 patients were compared by ultrasonography (US). Diagnosis of ICA occlusion with CCDS, PD and B-flow was correct in all 42 cases. A preocclusive ICA stenosis in DSA was detected correctly in all 48/48 cases (100%) for B-flow, in 44/48 (92%) for PD and in 39/48 (81%) for CCDS. Surgical findings showed in 17/42 cases ulcerated plaques; 15/17 (89%) of these cases were detected with B-flow, 12/17 (71%) with PD, 10/17 (59%) with CCDS, and 8/17 (47%) with DSA. With B-flow the extent of stenosis was appraised more precisely than with PD and CCDS (P<0.0001). In conclusion, B-flow is a reliable method for preocclusive stenosis of the ICA with less intrastenotic flow artefacts. B-flow facilitates the characterization of plaque morphologies.

[Significance of Doppler ultrasound procedures for diagnosis of carotid stenoses]

Determining degree and morphology of stenoses is important for surgical planning or stent implantation. Vascular ultrasound is usually the first modality to evaluate carotid artery stenosis. Due to rapid development various methods of vascular ultrasound are applied including continuous wave (CW) Doppler, duplex Doppler, colour-coded duplex sonography (CCDS), power Doppler and B-flow technique. For quantitative assessment of the degree of stenosis the most frequently used parameters are peak systolic velocity (PSV), end-diastolic velocity (EDV) in the internal carotid artery (ICA), as well as ICA to CCA ratios of PSV and EDV. Different results reported in the literature may reflect differences in defining the degree of stenosis and methodological differences in protocol or imaging techniques. Differences in defining the degree of stenosis, advantages and disadvantages of the different Doppler techniques and future developments are discussed in detail.