This is an angiogram of the arteries of the forearm. The contrast was injected via a catheter in the axillary artery/subclavian artery junction. The bolus of contrast is observed under flouroscopy and sequential images of the arm are taken to see the various arteries of the arm.
Note that the common, anterior and posterior interosseous arteries are not visualized. They are either not present or are diminutive. Normal arterial anatomic variants such as this exist.