![]() This value will increase as the ICA becomes more occluded.ĬHARACTERIZING ICA STENOSIS: SOCIETY OF RADIOLOGISTS IN ULTRASOUND (SRU) CONSENSUS ICA/CCA PSV ratio: this compares the ratio of blood flow in the ICA and CCA.It is measured in both the ICA and CCA as well to characterize stenosis of the ICA. End diastolic velocity (EDV): this measurement is made at the end of diastole to evaluate how quickly the blood is moving in the vessel in question.It is measured in both the internal carotid (ICA) as well as the common carotid artery (CCA) so that they may be compared to one another. Peak systolic velocity (PSV): this refers to how quickly the blood is traveling in the targeted vessel during systole.There are a number of quantitative measurements that are made during this study that help characterize the degree of stenosis later on. This page is dedicated providing useful information that can help aid in the interpretation of a carotid ultrasound study. 4 CHARACTERIZING ICA STENOSIS: THE NORTH AMERICAN SYMPTOMATIC CAROTID ENDARTERECTOMY TRIAL (NASCET INDEX).3 CHARACTERIZING ICA STENOSIS: SOCIETY OF RADIOLOGISTS IN ULTRASOUND (SRU) CONSENSUS.propylene glycol peak: resonates at 1.13 ppm.N-acetylaspartate (NAA) peak: resonates at 2.0 ppm.glutamine-glutamate peak: resonates at 2.2-2.4 ppm.gamma-aminobutyric acid (GABA) peak: resonates at 2.2-2.4 ppm.2-hydroxyglutarate peak: resonates at 2.25 ppm.arterial spin labeling (ASL) MR perfusion.dynamic contrast enhanced (DCE) MR perfusion.dynamic susceptibility contrast (DSC) MR perfusion.metal artifact reduction sequence (MARS).turbo inversion recovery magnitude (TIRM).fluid attenuation inversion recovery (FLAIR).diffusion tensor imaging and fiber tractography.MRI pulse sequences ( basics | abbreviations | parameters).iodinated contrast-induced thyrotoxicosis.iodinated contrast media adverse reactions.clinical applications of dual-energy CT.as low as reasonably achievable (ALARA).In this setting, a significant reduction in post-stenotic flow velocity is termed “trickle flow” 5. In complete occlusion, PSV and EDV are absent 4. To an extent, an increased degree (%occlusion) of stenosis corresponds to increased PSV and EDV 4. In near occlusion (>99%), flow velocity indices become unreliable (may be high, low or absent) 4. High flow velocity causes Reynolds number to increase beyond a critical point, resulting in turbulent flow which manifests as spectral broadening on Doppler ultrasound 3. In stenosis, a localized reduction in vascular radius increases resistance, causing increased PSV and EDV distal to the stenosed site 3,4. external carotid artery, limb arteries) are characterized by early reversal of diastolic flow, and low or absent EDV 4. In contrast, high resistance vessels (e.g. These vessels exhibit high diastolic flow and EDV 4. internal carotid artery, renal artery) supply end organs which require perfusion throughout the entire cardiac cycle. At angles >60 o, the cosine function curves much more steeply, leading to a significant reduction in the accuracy of angle correction, and thus the accuracy of blood velocity indices such as PSV and end-diastolic velocity (EDV) 1.įactors that influence flow velocity indicesįlow velocity may vary based on vessel properties and pathological changes 3,4. Since the trigonometric ratio that relates these values is the cosine function, it follows that the angle of insonation should be maintained at ≤60 o 1,2. The spectral Doppler system utilizes Fourier analysis and the Doppler equation to convert this shift into an equivalently large velocity, which appears in the velocity tracing as a “peak” 2.īy the Doppler equation, it is noted that the magnitude of the Doppler shift is proportional to the cosine of the angle (of insonation) formed between the ultrasound beam and the axis of blood flow 2. during systole), red blood cells exhibit their greatest magnitude of Doppler shift. When traveling with their greatest velocity in a vessel (i.e. Factors that influence flow velocity indices.
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