Search results
Results from the WOW.Com Content Network
Magnetic resonance angiography (MRA) is a group of techniques based on magnetic resonance imaging (MRI) to image blood vessels. Magnetic resonance angiography is used to generate images of arteries (and less commonly veins) in order to evaluate them for stenosis (abnormal narrowing), occlusions, aneurysms (vessel wall dilatations, at risk of rupture) or other abnormalities.
For all structures except the heart, the images are usually taken using a technique called digital subtraction angiography or DSA. Images in this case are usually taken at 2–3 frames per second, which allows the interventional radiologist to evaluate the flow of the blood through a vessel or vessels. This technique "subtracts" the bones and ...
Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a "pre-contrast image" or mask from subsequent images, once the contrast medium has been introduced into a ...
See also: Digital variance angiography. The diagnostic value of radiographic images is limited by image quality, which can be measured through signal-to-noise ratio (SNR) calculations. The higher the value of SNR, the better the image. The SNR can be increased initially by enhancing the "signal" or "contrast", which is the intensity difference ...
Baseline color and black and white red-free filtered images are taken prior to injection. The black and white images are filtered red-free (a green filter) to increase contrast and often gives a better image of the fundus than the color image. A 6-second bolus injection of 2-5 cc of sodium fluorescein into a vein in the retina; Local injection
Flow-mediated dilation (FMD) refers to dilation (widening) of an artery when blood flow increases in that artery. [1] [2] The primary cause of FMD is release of nitric oxide by endothelial cells. [1] To determine FMD, brachial artery dilation following a transient period of forearm ischemia is measured using ultrasound. [3]
Comparison of kinetic images(KIN) and DSA images in abdominal (top row) and iliac regions (bottom row). Digital variance angiography (DVA) is a novel image processing method based on kinetic imaging, which allows the visualization of motion on image sequences generated by penetrating radiations. DVA is a specific form of kinetic imaging: it ...
Initial efforts to measure blood flow using OCT utilized the Doppler effect. [41] [42] By comparing the phase of successive A-mode scans, the velocity of blood flow can be determined via the Doppler equation. This was deemed Optical Doppler Tomography; the development of spectral domain OCT (SD-OCT) and swept-source OCT (SS-OCT) greatly ...