![]() Two studies included healthy people who had no previous vascular diseases or other risk factors. Some studies have identified the normal IMT values in the Korean population. Although normal IMT values among Koreans have been reported, large-scale studies are needed to predict cardio-cerebrovascular disease risk. They can also differ according to the type of measurement method used. Normal IMT values depend on age, sex, and race. However, waveform oscillations induced by temporal tapping can be found beyond the ECA in the CCA and ICA, especially in diseased ICAs. This so-called temporal tapping is a useful method for differentiating between the ICA and ECA ( Fig. This temporal artery tapping-induced artifact is generally not observed in the normal ICA Doppler spectrum. Another method for differentiating the ECA from the ICA involves placing the fingertips on the ipsilateral temporal artery when obtaining the ECA Doppler spectrums, which generates a serration-like artifact. The velocity difference between the systolic and diastolic phases of the blood is smaller in the ICA than in the ECA. The Doppler spectrums of the ICA indicated lower resistance patterns ( Fig. The proximal ICA does not have branches, while the ECA does. In contrast, the ECA is located superficially and is directed toward the face. The ICA has a larger diameter, is located deeper than the ECA, and is directed toward the mastoid process. ![]() Then, observe the shape of the carotid artery in the longitudinal view. 5 The flow direction is generally the same as the vessel direction, but it can differ from the vessel direction when eccentric atherosclerotic plaques are present.įirst, in the cross-sectional view, trace the carotid artery from the proximal CCA to the distal internal carotid artery (ICA) and then the external carotid artery (ECA), or vice versa. Angle correction is crucial for measuring the actual flow velocity, which should be performed along the flow direction instead of the vessel wall. The peak velocity is measured to detect significant stenosis. 1 Pulse-wave Doppler is needed to precisely measure flow velocity, and uses a small sample volume from the vessel center to assess the velocity at that segment. This is called the heel-and-toe technique, and is a method for steering probes. Pushing the head- or foot-side edge creates an angle between the probe surface and the vessel, which can achieve the optimal Doppler angle. 1 In most patients, the probe surface runs parallel to the common carotid artery (CCA) in its usual position, which allows scanning of the carotid artery without applying pressure. However, to accurately record velocity using color Doppler ultrasonography, the angle must be between 30° and 60°. The ultrasound beam should be perpendicular to the skin, with a linear probe generating a grayscale image. Placing a pillow induces a poor evaluation window for the carotid artery and therefore normally should not be used.Īn adequate acoustic angle is important in obtaining an accurate color Doppler image. The neck of the patient should be relaxed and the chin should be slightly raised. Tilting the face too far from the test site can distort the anatomy or compress blood vessels, especially veins. The optimal position for tilting the head of the patient is approximately 45° away from the relevant artery. However, obtaining right-posterior projections is difficult. This position makes it easy to control the ultrasound probe. The examiner generally uses their right hand to evaluate both carotid arteries. A lateral sitting position is used for most ultrasonography examinations. ![]() However, the examiner should be familiar with the practice of using both hands. This position provides an expanded sonic window with a clear view of the carotid artery and allows many ultrasound probing positions. 1 In the overhead position, the examiner sits behind the head of the patient beside the end of the bed and uses both hands in the test. ![]() The examiner can observe the carotid artery from either an overhead or a lateral sitting position.
0 Comments
Leave a Reply. |