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Atlas of Human Body Ultrasound Scanning_ Methods and Diagnostic Applications ( PDFDrive ).pdf
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7  Vascular System Scanning

129

 

 

1.5.1\ Scanning Method

The subject takes a supine position with the head slightly stretched to make a full extension of the neck. The probe is placed transversely on the lateral or the posterolateral neck, and scanning is performed from bottom to top. The transverse section of the bifurcation of the common carotid artery is shown. The internal carotid artery is located at the posteroexternal neck, and the external carotid artery is located at the anteromedial neck.

1.5.2\ Sectional Structure

Transverse section of the internal carotid artery and the external carotid artery. In general, the internal carotid artery is the wider one and located posterolateral to the neck; the external carotid artery is the finer one and located anteromedial to the neck.

1.5.3\ Measurement Methods

Measuring the intima-media thickness (IMT), diameter, and blood flow spectrum of the carotid artery.

1.5.4\ Clinical Significance

Showing the anatomic location and the situation of the wall and lumen of the carotid artery, which is used to observe the eccentric plaque and to calculate the stenosis rate.

1.5.5\ Note

It is reported that about 60% of the internal and external carotid artery can be displayed in the same plane in the level of bifurcation, and only one blood vessel can be displayed in the level of the common carotid artery. In general, the external carotid artery is fine and has branches, and the superior thyroid artery is the first branch which is easy to be observed. The internal carotid artery is usually wide and has no branches.

130

B. Su and Q. Yong

 

 

1.6\ Pulsed-Doppler Spectrum

of the Internal Carotid Artery

Fig. 7.6  Doppler spectrum of the internal carotid artery

1.6.1\ Scanning Method

The subject takes a supine position with the head slightly stretched to make a full extension of the neck. The probe is placed on the posterolateral neck behind the sternocleidomastoid and the sound beam directly from the anteromedial to the sternocleidomastoid muscle. The longitudinal section of the bifurcation of the common carotid artery is shown, and scanning is performed from bottom to top. The internal carotid artery is located posterolateral to the neck; the external carotid artery is located anteromedial to the neck. The pulse-Doppler sample volume is placed in the middle of the artery, and the Doppler beam correction angle θ line parallels to the beam flow line as far as possible; the angle should be no more than 60.

1.6.2\ Section Structure

A positive three-peak waveform. The resistance index of the internal carotid artery is lower.

1.6.3\ Measurement Methods

Measuring the peak velocity and resistance index of the blood flow spectrum.

1.6.4\ Clinical Significance

According to the spectrum shape, blood flow velocity, and resistance index, we can:

1\ .\ Distinguish the internal carotid artery from the external carotid artery. The blood flow pattern is the most effective index to identify the two arteries, especially to the internal carotid artery occlusion. If Doppler spectrum of two vessels is similar in carotid bifurcation, and the resistance index is the same or similar, the internal carotid artery may be in occlusion, while the two vessels may be the external carotid artery and its branch.

2\ .\ Determine whether there is an artery stenosis or not.

\3.\ Judge whether there is stenosis, occlusion, or arteriovenous fistula in the distal vessels.