3D RA vs 2D DSA in Brain Arteriovenous Malformations

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The brain arteriovenous malformations (BAVM) are an important cause of nontraumatic intracranial hemorrhage, especially in the younger population. Detailed angioarchitecture evaluation is prerequisite for management planning of these vascular malformations. Digital subtraction angiography (DSA) being the gold standard in the evaluation of intracranial vascular pathologies including BAVM, aneurysms, and arteriovenous fistulas (AVF) and 2D DSA in multiple projections is being used for years for evaluation of BAVM, aneurysms, and AVFs. In the present article, the authors have shown that the use of 3D rotational angiography (RA) for BAVM and have done a critical evaluation of this technique over 2D DSA.[1] Vascular angiographic evaluation of BAVM includes features like the number of arterial feeders, nidus characteristics, presence of arterial aneurysms (flow-related or nidal), direct fistulous connections, venous sacs, venous stenosis, and drainage, these help in the understanding of its natural history and assists in deciding most suitable ways to deal with these complicated vascular pathologies.[2] Conventional 2D DSA because of complex anatomy, high flow, and vascular overlaps give a suboptimal angioarchitectural depiction of these malformations. To overcome this suboptimal evaluation done with 2D DSA, 3D RA came into existence which partially overcame this limitation. 3D RA technique was primarily used for evaluation of intracranial aneurysms in defining aneurysmal morphology, neck evaluation, and its relation and angle with afferent and efferent arteries. 3D RA has revolutionized the way endovascular management is being done for aneurysms with advanced interventional armamentarium which includes flowdivertor and intrasaccular devices like WEB. Relatively less work has been done for assessment of the role of 3D RA in BAVM evaluation. Use of 3D RA significantly increases the chances of picking up nidal aneurysms, fistulous connections, venous stenosis, and venous sacs besides providing better details of arterial feeders and venous drainage. Since all these factors predict the risk of hemorrhage in BAVM so these are considered important angiographic predictors influencing the natural history of the disease thereby helping the interventionist in terms of therapeutic decision making.[1,3] In our experience, we have found that 3D RA is superior to 2D DSA when it comes to detection of nidal aneurysms and venous stenosis. There is no significant advantage of 3D RA in the depiction of numbers of major arterial feeders and draining veins. One major limitation of 3D RA is its inability to provide information about BAVM hemodynamics in real-time, to overcome this limitation a concept of 4D DSA came where vascular reconstruction can be done at any time and at any desired projection angle you want for better depiction of the vascular angioarchitecture.[4,5] Angiographic evaluation of any brain AVM begins with 2D DSA but in large vascular malformations there is very high flow obscuring the angioarchitectural details of the malformation and to overcome this, DSA is done at higher frame rate (6-10 frame/sec) at multiple projections but then also vascular overlaps hide much strategic information. To evaluate further microcatheter angiograms of different feeding vessels at various projections is being done to understand the complex anatomy of many brain AVM. 3D RA overcomes the requirement of various projections but the vascular overlap is there as it is not time-resolved. Time-resolved 3D RA is practically 4D DSA which gives 3D information at the desired time and projection.[4,5] Identifying fistulous component by 3D RA as reported by the author is to be more than with 2D angiogram but we feel micro catheter selective angiogram is best for it. 2D DSA scores over 3D RA when evaluating dural AVM in terms of assessing cortical venous reflux and also blood redistribution through collaterals whereas 3D RA better depicts structural details like feeding artery aneurysms and dysplastic changes in the feeding artery, presence of nidal aneurysms, direct fistulous connections and venous stenosis in the evaluation of pial BAVM. Nidal angioarchitecture details can be evaluated by 3D RA when nidus is small or slow vascular shunts are there but in large and high flow shunts 4D RA would be better but is still underutilized. Whereas 2D DSA in addition to structural details, also provides information about hemodynamics that is a functional part of BAVM, which helps the interventionist to realize the degree of venous stenosis and in turn estimate the risk hemorrhage. Thus, both these modalities (2D DSA and 3D RA) are complementary to each other for a more detailed evaluation of BAVM. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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