I. Introduction
Ultrasound guided procedures are increasingly being used for the diagnosis and treatment of disease. In current guided needle procedures, the practitioner first identifies the region of interest using an ultrasound probe. Once the desired anatomy is in view, the practitioner estimates a needle trajectory and insertion point. The needle is then inserted and the practitioner adjusts the ultrasound probe to achieve visualization of the needle. A challenge with ultrasound-guided procedures is continuous visualization of the needle during the entire procedure. The full length of the needle must be completely maintained within the lmm wide ultrasound beam. The inability to properly identify the needle tip, as depicted in Fig. 1, makes it dangerous to advance the needle. For example, improper needle placement has led to life threatening seizures, pneumothoraces, arterial dissections, and failed nerve blocks [1]. Once the practitioner achieves adequate needle visualization, he or she uses a “freehand” technique to complete the procedure. The term “freehand” is used to describe a technique where the practitioner has complete flexibility with insertion points and approach angles to avoid damaging important structures (such as arteries) and/or inject medication in different locations. Currently, many of these procedures are limited to more experienced practitioners mainly due to the fine motor skill needed to maintain needle imaging for safe placement [2].