Reusable Phantom With Feedback Signal for Ultrasound Needle Tip Control Accepted for Publication: 17 June 2011 To the Editor: P recise dexterity is an essential techni- cal skill to properly align and track the block needle when performing ultrasound- guided regional anesthesia. This skill is most effectively acquired through hands-on practice. 1 Several training phantoms 2 have been developed to shorten the learning curve and provide learners with the oppor- tunity to refine their needle guidance skills. However, most phantoms do not provide feedback for learners to help distinguish whether the needle tip or the shaft is con- tacting the target. We have developed a simple and eco- nomical phantom that allows learners to practice maneuvering the needle tip un- der ultrasound guidance. This model uses a common commercial nerve stimulator to provide immediate feedback when the tipVnot the needle shaftVcomes in contact with the target wire. The phantom on its own is an incomplete electrical circuit made up of metal wire embedded in a liquid gel. When the tip of the needle comes in contact with the target wire, the circuit is complete. This triggers a signal that lets the learner know that they have contacted their target with the appropriate part of the needle. To construct this phantom (Fig. 1), we obtained a heat-resistant glass con- tainer and suspended a metal wire, formed into the appropriate shape, in an empty container with one end of the wire posi- tioned outside the area of the container. Melted gel (Gel Wax; Yaley Enterprises, Redding, Calif) colored with dye (Blue Liquid Candle Dye; Yaley Enterprises) to achieve the desired opacity was poured into the container to cover the suspended wire, leaving one end of the wire ex- posed. The ground electrode was then connected to the exposed wire while the insulated needle (Sonoplex Needle; Pajunk Medizintechnologie, Geisingen, Germany) was connected to the nerve stimulator (Stimuplex HNS 12; B-Braun, Melsugen, Germany). This system uses a similar setup to that of the nerve stimulator used in practice. Using ultrasound visualiza- tion, the embedded metal appears predom- inantly hyperechoic, round in short axis, and cable-like in long axis (Fig. 2). The target size can be varied by chang- ing the diameter of the wire, providing a challenge appropriate to the skill level of the learner. This phantom can then be seated with a lid and stored for an extended period. This nonorganic phantom has the following advantages over other training models 3,4 : (1) it is affordable and simple to maintain; (2) after repeated needle punctu- res, needle-track artifacts can be easily re- moved by remelting the phantom in any conventional oven; (3) the gel can be dyed to a desired opacity to allow the learner to visualize the target under different condi- tions; and (4) there is immediate feedback for the learner when the needle tip touches the target, which is independent from the ultrasound image. However, the model has disadvantages, one of which is that the gel medium does not accurately represent hu- man tissue because of different echogenic properties when visualized using ultra- sound. This may result in the needle ap- pearing to be of different brightness in the gel when compared with actual human tissue. 5 Nevertheless, the described setup, using metal wire in conjunction with a nerve stimulator, can be inserted into other tissue types, such as pork, to provide a more realistic simulation. Ban C.H. Tsui, MD, MSC Jenkin Tsui Department of Anesthesiology and Pain Medicine University of Alberta Edmonton, Canada REFERENCES 1. Xu D, Abbas S, Chan VW. Ultrasound phantom for hands-on practice. Reg Anesth Pain Med. 2005;30:593Y594. 2. Hocking G, Hebard S, Mitchell CH. A review of the benefits and pitfalls of phantoms in ultrasound-guided regional anesthesia. Reg Anesth Pain Med. 2005;36:162Y170. 3. Patel AS, Harrington TJ, Saunt KS, Jones WK. Construction of an ultrasound FIGURE 2. Phantom in use. FIGURE 1. Phantom materials and setup. LETTERS TO THE EDITOR 630 Regional Anesthesia and Pain Medicine & Volume 36, Number 6, November-December 2011 Copyright © 2011 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.