A sterile, small-diameter, single-lumen, flexible tube designed for the controlled infusion of fluids (e.g., thrombolytics, diagnostic contrast media) into superselective small vessels (including intracranial, peripheral, or occluded coronary vasculature) for angiography/treatment, and typically also for the delivery of devices (e.g., embolization implants, guidewires) into tortuous vessels or across tight lesions. It may include an ultrasound transducer, a thermal sensor, and a hole for guidewire placement located at the distal tip. It is not a guide-catheter (i.e., is not intended to deliver other catheters or therapeutic leads directly through its lumen). This is a single-use device.