Figure 3. Schematic shows study design for an empirical RCT to compare CT angiography (CTA) with intraarterial DSA (Angio) for pretreatment diagnostic imaging work-up of peripheral arterial disease. After randomization, either CT angiography or intraarterial angiography (in a few cases followed immediately by percutaneous transluminal angioplasty or stent placement [+/-PTA/stent]) is performed. The imaging findings are discussed at the vascular conference. The imaging work-up is required to help determine the optimal treatment: percutaneous transluminal angioplasty, stent placement, bypass surgery, or exercise therapy. The dotted arrows indicate where subjective experience is expected to influence the clinical process. duplex = duplex ultrasonography, +/- = with or without.