A 55-year-old man with a 12-year history of type 2 diabetes mellitus and hypertension presents to the emergency department with sudden onset of left lower limb pain and coldness. On examination, the left foot is pale and pulseless distal to the femoral artery. Digital subtraction angiography (DSA) is performed and reveals a focal, eccentric, irregular narrowing of the superficial femoral artery with overhanging edges and a contrast-filled ulceration. Which of the following angiographic findings is MOST specific for the underlying pathology?