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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.
Angiography is also commonly performed to identify vessels narrowing in patients with leg claudication or cramps, caused by reduced blood flow down the legs and to the feet; in patients with renal stenosis (which commonly causes high blood pressure) and can be used in the head to find and repair stroke. These are all done routinely through the ...
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 ...
The physician steers the guidewire from outside the body, through angiography catheters and into the blood vessel branch to be imaged. The ultrasound catheter tip is slid in over the guidewire and positioned, using angiography techniques so that the tip is at the farthest away position to be imaged. The sound waves are emitted from the catheter ...
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 ...
Angiography: Sometimes referred to as traditional angiography, catheter angiography or digital subtraction angiography (DSA). A small needle is inserted into a blood vessel, then exchanged for a catheter over a wire. The catheter is directed at the vessel to be studied, and contrast is directly injected to evaluate the lumen under video X-ray.
A scanning fiber endoscope is a technology that uses a flexible, small (< 6Fr) peripheral or coronary catheter to provide wide-field, high-quality, full-color, laser-based video imaging. These differences distinguish SFE applications from current imaging approaches such as IVUS and Intracoronary OCT .
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 ...