The polony phantom: a cost-effective aid for teaching emergency ultrasound procedures
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- Wells, M. & Goldstein, L. Int J Emerg Med (2010) 3: 115. doi:10.1007/s12245-009-0156-1
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Central venous access and nerve blockade are essential skills in the practice of emergency medicine, and the utility of emergency ultrasound to guide these procedures has been well demonstrated.
A phantom is a valuable tool to learn and develop the dexterity for ultrasound-guided techniques.
To date, the time and cost required to produce or purchase such models has somewhat limited their use.
A time- and cost-effective alternative using polony and common household items is presented.
KeywordsImaging phantoms Ultrasonography central venous catheterisation Nerve block Emergency ultrasound
The use of emergency ultrasound (EUS) to assist with vascular access techniques is advocated by many organisations across the world including the American College of Emergency Physicians, the College of Emergency Medicine in the UK, the Australasian College of Emergency Medicine and the College of Emergency Medicine of South Africa. EUS has been shown to increase the success rate and decrease the complication rate of central venous cannulation  as well as plexus and peripheral nerve blockade.  These techniques should therefore be included in the instruction of basic and intermediate EUS. A phantom is generally used for the practical component of this teaching to encourage the development of appropriate hand-probe-eye co-ordination, but commercial phantoms are expensive and previously described home-made phantoms require time, skill and the availability of the necessary materials to assemble. [3, 4, 5, 6]
We have developed a simple vascular access/nerve block phantom made from a polony (bologna) roll that can be constructed within 5 minutes with minimal skill and without the need for other materials.
To create the nerve phantom, we inserted a thin wire from one end of the polony to the other. We then attached a 600-mm woven nylon shoelace to the end of the wire and pulled the lace back through the polony. This was done with the polony submerged underwater to prevent air entry into the tract. Tape was put on each end of the shoelace tract in order to create a watertight seal.
In order to give a “hands-on” feel when learning to cannulate vessels and perform nerve blocks via ultrasound guidance, various alternatives have been suggested to maintain the realism of the training model. Existing designs for training aids have varied from gelatine-based recipes for phantoms (home-made and commercially available) to the use of a number of different animal tissues. The dexterity required to juggle the ultrasound probe whilst performing procedures needs to be taught and practised prior to its application on a real patient. The ideal phantom should be inexpensive, simple to construct, not be time-consuming to produce and have a sonographic appearance similar to human tissue.
Most recipes for home-made phantoms are gelatine-based and require several hours of preparation time prior to use. Although animal tissue phantoms can allow for the practical feel of human tissue, they are expensive and very time-consuming to construct. Commercially produced phantoms are generally expensive in comparison to the cost of the polony phantom (the equivalent of US$2 in South Africa).
Since not all polonies produce the same quality of ultrasound images, it may be necessary to experiment with several products until an ultrasound-friendly brand is identified.
The polony phantom is a solution to the problem of lengthy preparation times or the expense of other types of phantoms, while still fulfilling the other requirements of an acceptable ultrasound teaching aid.