ANSWER KEY FOR UNFILLED KEY TERMS DOCUMENT. Perfect for ultrasound instructors!! This study tool will help the students understand the basics of sonographic principles. Includes: a. Ultrasound Definition b. Pulse-Echo Technique. c. Echogenicities d. Echotextures e. Body planes f. Directional Terms g. Image Orientation. Downloadable PDF comes with actual answers and free of "Do Not Copy".