Digital subtraction angiography
- Images are produced using contrast medium by subtracting a ’pre-contrast image’ or the mask from later images, once the contrast medium has been introduced into a structure.
- Applications: DSA, is primarily used to image blood vessels. It is useful in the diagnosis and treatment of:
* Arterial and venous occlusions, including carotid artery stenosis, pulmonary embolisms and acute limb ischaemia.
* Arterial stenosis, which is particularly useful for potential renal donors in detecting renal artery stenosis.
* Cerebral aneurysms and arterio-venous malformations (AVM).
- The future: DSA is being used less and less routinely in imaging departments. It is being taken over by Computed Tomography Angiography (CTA), which can produce 3D images through a test which is less invasive and stressful for the patient.

Plz visit: Digital subtraction angiography - Wikipedia

Computed Tomography Angiography
- Computed tomography angiography (CTA) is a computed tomography technique used to visualize arterial and venous vessels throughout the body. This ranges from arteries serving the brain to those bringing blood to the lungs, kidneys, arms and legs.
- Clinical Applications:
* Examine the pulmonary arteries in the lungs to rule out pulmonary embolism, a serious but treatable condition.
* Visualize blood flow in the renal arteries (those supplying the kidneys) in patients with high blood pressure and those suspected of having kidney disorders.
* Identify aneurysms in the aorta or in other major blood vessels.
* Identify dissection in the aorta or its major branches.
* Identify a small aneurysm or arteriovenous malformation inside the brain that can be life-threatening.
* Detect atherosclerotic disease that has narrowed the arteries to the legs.
* Detect thrombosis (clots) in veins, for example large veins in the pelvis and legs. Such clots can travel to the lungs and result in pulmonary embolism.
- Benefits
* CTA can be used to examine blood vessels in many key areas of the body, including the brain, kidneys, pelvis, and the lungs.
* This method displays the anatomical detail of blood vessels more precisely than magnetic resonance imaging (MRI) or ultrasound.
* CTA is a useful way of screening for arterial disease because it is safer and much less time-consuming than catheter angiography and is a cost-effective procedure.
- Risks
* There is a risk of an allergic reaction.
* CTA should be avoided in patients with kidney disease or severe diabetes, because x-ray contrast material can further harm kidney function.
* If a large amount of x-ray contrast material leaks out under the skin where the IV is placed, skin damage can result.

Plz visit: Computed tomography angiography - wikipedia.