Definition: Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.
Input: Abstract: Digital subtraction angiography is a new imaging technique that uses a computer to subtract background distractions and to enhance contrast and density. The intravenous administration of contrast material permits safe outpatient screening for arterial disease. The exact role of intravenous digital subtraction angiography in cerebrovascular disease is still in evolution and remains the subject of debate. The value of intravenous digital subtraction angiography in screening for renovascular hypertension is less controversial, but selection of patients remains a subject for further study. Intra-arterial digital subtraction angiography has become a standard imaging technique that offers both the inherent safety produced by reduction of the volume of contrast material and the added safety afforded by reduction of both the size of the catheter and the time required to perform complex arterial interventional procedures. With the evolution of more sophisticated computed technology and radiographic equipment, the impact of both intravenous and arterial digital subtraction angiography will become even more dramatic.

Digital subtraction angiography.