This procedure is similar to the techniques used in arteriography but uses the image intensifier and computers to obtain rapid digital information as the contrast medium passes through the arteries. The computer is able to subtract the bones and other tissues, leaving only the vessels filled with contrast medium in the image, thus improving greatly the clarity and detail of the examination.
These angiographies can be performed only in highly sophisticated and dedicated vascular catheterization laboratories. Intra–arterial DSA reduces drastically the dose / volume of contrast and the radiation exposure to the patient and permits use of smaller and safer catheters. Intravenous DSA can be performed as a screening procedure on an OPD basis for lesions such as carotid stenosis / renal artery thrombosis. It is also useful for left ventriculography and for postoperative angiography to check grafts and follow–up of angioplasty.