====== Digital subtraction angiography ======

Digital subtraction [[angiography]] ([[DSA]]) is a type of [[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 the mask from later images, once the contrast medium has been introduced into a structure. Hence the term 'digital subtraction angiography.

DSA identifies vascular pathology in 13% of patients with CTA-negative SAH. [[Intracranial aneurysm]]s or pseudoaneurysms are identified in an additional 4% of patients by repeat [[DSA]] following an initially negative DSA. All patients with CT-negative SAH should be considered for DSA. The pattern of SAH may suggest the cause of hemorrhage, and aneurysms should specifically be sought with diffuse or [[perimesencephalic subarachnoid hemorrhage]]
((Heit JJ, Pastena GT, Nogueira RG, Yoo AJ, Leslie-Mazwi TM, Hirsch JA, Rabinov 
JD. Cerebral Angiography for Evaluation of Patients with CT Angiogram-Negative
Subarachnoid Hemorrhage: An 11-Year Experience. AJNR Am J Neuroradiol. 2015 Sep
3. [Epub ahead of print] PubMed PMID: 26338924.
)).

===== 3D-DSA =====

see [[3D-DSA]].