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Here the flow is either modulated by the respiratory rhythm or is continuous in cases where the flow is high. The thinner veins do not have a spontaneous flow. Vein valve and spontaneous contrast. However, in some circumstances the blood flow is so slow that it can be seen as some echogenic material moving within the vein, in "spontaneous ...
In "retrograde" flow, the flow would reverse (e.g. veins flow away from heart or arteries flow towards the heart). However, "retrograde" flow can be both abnormal or normal. For example, in portal hypertension, there is an abnormal portal venous flow where it flows away from the liver (hepatofugal flow) instead of the normal flow towards liver ...
Intravascular ultrasound image of a coronary artery (left), with color-coding on the right, delineating the lumen (yellow), external elastic membrane (blue) and the atherosclerotic plaque burden (green). The percentage stenosis is defined as the area of the lumen (yellow) divided by the area of the external elastic membrane (blue) times 100.
Apical four chamber ultrasound view of heart. Transthoracic echocardiography (TTE) uses ultrasonic waves for continuous heart chamber and blood movement visualization. It is the most commonly used imaging tool for diagnosing heart problems, as it allows non-invasive visualization of the heart and the blood flow through the heart, using a technique known as Doppler.
ICE catheters are limited in size as they must be introduced inside the blood vessels. Limitation of the size of the catheter limits the ultrasound crystal and the image quality obtainable. However, because the catheter can be readily moved into close proximity of the desired structure, the quality limitation can be reduced. [citation needed]
Echocardiography, also known as cardiac ultrasound, is the use of ultrasound to examine the heart. It is a type of medical imaging , using standard ultrasound or Doppler ultrasound . [ 1 ] The visual image formed using this technique is called an echocardiogram , a cardiac echo , or simply an echo .
A dilated portal vein (diameter of greater than 13 or 15 mm) is a sign of portal hypertension, with a sensitivity estimated at 12.5% or 40%. [18] On Doppler ultrasonography, a slow velocity of <16 cm/s in addition to dilatation in the main portal vein are diagnostic of portal hypertension. [19]
The human hepatic portal system delivers about three-fourths of the blood going to the liver.The final common pathway for transport of venous blood from spleen, pancreas, gallbladder and the abdominal portion of the gastrointestinal tract [2] (with the exception of the inferior part of the anal canal and sigmoid colon) is through the hepatic portal vein.