Changes in ultrasonographic echogenicity and visibility of needles with changes in angles of insonation. 
To objectively compare the echogenicity of several types of needles at clinically important angles of insonation.  Four commercial needles (Echotip, Mini-Stick, Echo-Coat, Surflo) and a prototype dimpled needle were tested in a liver phantom at angles of insonation ranging from 90 degrees to 15 degrees.  Photodensity measurement determined echogenicity levels in arbitrary echogenicity units (EU).  At 90 degrees angles of insonation all needles were easily seen (60-76 EU) and echogenic levels were similar (P =.264).  All values decreased with angulation.  From the 35 degrees to 15 degrees angles, the prototype and Echotip needles were superior (P <.05).  At 15 degrees the values were 43 EU for the prototype needle, 40 EU for the Echotip needle, 9.0 EU for the Echo-Coat needle, and 5.0 EU for the Surflo needle.  With angulation, all needles drop in echogenicity, with prototype dimpled and Echotip best maintaining visibility at clinically important angles.