The retreating-stop needle guide as an alternative to variable-angle needle guides

A new type of needle guide, a retreating-stop needle guide, is proposed and compared with existing variable-angle style needle guides. Compared to existing designs, this design gives the user finer control over the depth of needle insertion as well as preventing excessive needle advancement. For a subset of ultrasound guided procedures, particularly those that may benefit from out-of-plane approaches, retreating-stop needle guides could potentially improve needle placement. A prototype retreating-stop needle guide was constructed which has measurement resolution of 5mm and a depth range of 3.0-7.5 cm, which is superior to commonly available existing needle guides. Resolutions of 2-3mm are theoretically possible with this technique.