title: Modeling, Production, and Testing of an Echogenic Needle for Ultrasound-Guided Nerve Blocks.
abstract: We have designed, produced, and tested an echogenic needle based on a sawtooth pattern where the height of the tooth was 1.25 times the wavelength of the ultrasound transducer. A numeric solution to the time-independent wave equation (Helmholtz equation) was used to create a model of backscattering from a needle. A 21-gauge stainless steel prototype was manufactured and tested in a water bath. Backscattering from the needle was compared to theoretical predications from our model. Based on these results, an 18-gauge prototype needle was fabricated from stainless steel and tested in a pig cadaver. This needle was compared to a commercial 18-gauge echogenic needle (Pajunk Medical Systems, Tucker, GA) by measuring the brightness of the needle relative to the background of sonograms of a needle in a pig cadaver. The backscattering from the 21-gauge prototype needle reproduced the qualitative predictions of our model. At 30° and 45° of insonation, our prototype performed equivalently to the Pajunk needle. At 60°, our prototype was significantly brighter than the Pajunk needle (P = .017). In conclusion, we chose a model for the design of an echogenic needle and modeled it on the basis of a solution to the Helmholtz equation. A prototype needle was tested in a water bath and compared to the model prediction. After verification of our model, we designed an 18-gauge needle, which performed better than an existing echogenic needle (Pajunk) at 60° of insonation. Our needle will require further testing in human trials.
authors.affiliation: Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, Maryland USA pbigeleisen@anes.umm.edu.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Bigeleisen
authors.affiliation: Department of Anesthesiology, University of Wisconsin School of Medicine, Madison Wisconsin USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Hess
authors.affiliation: Department of Anesthesiology, Yale University, New Haven, Connecticut USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Zhu
authors.affiliation: Department of Anesthesiology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Annelot
authors.initials: A
authors.lastname: Krediet
mesh_terms: D000818:Animals; D004867:Equipment Design; D008954:Models, Biological; D009339:Needles; D009407:Nerve Block / Q000295:instrumentation*; D013552:Swine; D018084:Ultrasonography, Interventional / Q000379:methods*
keywords: Helmholtz equation; echogenic needle; ultrasound; ultrasound-guided nerve blocks