ANGIOGRAPHY


DEFINITION

A medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins and the heart chambers. The word itself comes from the Greek words angeion, "vessel", and graphein, "to write" or "record".

HOW IT WORKS

This is traditionally done by injecting a radio-opaque contrast agent into the blood vessel and imaging using X-ray-based techniques such as fluoroscopy.

Depending on the type of angiogram, access to the blood vessels is gained most commonly through the femoral artery, to look at the left side of the heart and at the arterial system; or the jugular or femoral vein, to look at the right side of the heart and at the venous system. Using a system of guide wires and catheters, a type of contrast agent (which shows up by absorbing the X-rays), is added to the blood to make it visible on the x-ray images.

The X-ray images taken may either be still, displayed on an image intensifier or film, or motion images.

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 other organs so only the vessels filled with contrast agent can be seen. The heart images are taken at 15–30 frames per second, not using a subtraction technique. Because DSA requires the patient to remain motionless, it cannot be used on the heart. Both these techniques enable the interventional radiologist or cardiologist to see stenosis (blockages or narrowings) inside the vessel which may be inhibiting the flow of blood and causing pain.

WHEN ITS USED

  • Coronary Angiography (to visualize the blood in the coronary arteries)

  • Microangiography (to visualize tiny blood vessels)

  • Neuro-vascular digital subtraction angiography (o visualise the arterial and venous supply to the brain, Intervention work such as coil-embolisation of aneurysms and AVM gluing can also be 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

  • Placement of a PICC (peripherally inserted central catheter)

  • Placement of a weighted feeding tube (e.g. Dobhoff) into the duodenum after previous attempts without fluoroscopy have failed.

  • Urological surgery – particularly in retrograde pyelography.

  • Cardiology for diagnostic angiography, percutaneous coronary interventions, (pacemakers, implantable cardioverter defibrillators and cardiac resynchronization devices)

  • Discography, an invasive diagnostic procedure for evaluation for intervertebral disc pathology.

RISKS AND BENEFITS

  • The contrast medium that is used usually produces a sensation of warmth lasting only a few seconds, but may be felt in a greater degree in the area of injection.

  • The patient may be allergic to the medium.

  • Damage to blood vessels can occur at the site of puncture/injection, and anywhere along the vessel during passage of the catheter (If digital subtraction angiography is used instead, the risks are considerably reduced because the catheter does not need to be passed as far into the blood vessels; thus lessening the chances of damage or blockage).

CORONARY ANGIOGRAPHY

One of the most common angiograms performed is to visualize the blood in the coronary arteries. A long, thin, flexible tube called a catheters ram is used to administer the X-ray contrast agent at the desired area to be visualized. The catheter is threaded into an artery in the forearm, and the tip is advanced through the arterial system into the major coronary artery. X-ray images of the transient radiocontrast distribution within the blood flowing inside the coronary arteries allows visualization of the size of the artery openings. Presence or absence of atherosclerosis or atheroma within the walls of the arteries cannot be clearly determined.

To detect coronary artery disease, Computed Tomography (CT) Scan is better than Magnetic Resonance Imaging (MRI). The sensitivity and specificity between CT and MRI were (97.2 percent and 87.4 percent) and (87.1 percent and 70.3 percent), respectively. Therefore, CT (mainly multislice CT) is more accepted, more widely available, more favored by patients, and more economic. Moreover, CT requires shorter breath-hold time than MRI.

A fluorescein angiography is a medical procedure in which a fluorescent dye is injected into the bloodstream. The dye highlights the blood vessels in the back of the eye so they can be photographed. This test is often used to manage eye disorders.

https://en.wikipedia.org/wiki/Angiography

#imaging #RADIOGRAPHY

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