Fig. 5From: Use of ultrasound guidance to improve the safety of percutaneous dilatational tracheostomy: a literature reviewTransverse view at the level of the suprasternal notch (SSN) showing the trachea and the thyroid gland. A-M, air-mucosal interface; CTA, comet tail artefact; Is, isthmus; TG, thyroid gland; Trc, tracheal cartilage (ring). Reprinted with permission from Wolters Kluwer [42]Back to article page