This e-book is intended to supplement education and training of vascular vessel mapping protocols for creation of an endovascular arteriovenous fistula (endoAVF) utilizing the approach with dual magnetic catheters and application of radiofrequency energy to create an endoAVF (dual catheter system) anastomosis. Vessel mapping is an important step in identifying patients who can successfully receive an endoAVF (dual catheter system). Sonographers play a vital role in this process by accurately screening and communicating results to the physician to determine which patients are potential candidates.