title: Effect of beam steering on the visibility of echogenic and non-echogenic needles: a laboratory study.
abstract: OBJECTIVE
  During peripheral nerve block procedures, needle visibility decreases as the angle of needle insertion relative to skin increases due to loss of reflective signals. The primary aim of our study was to compare the effect of beam steering on the visibility of echogenic and non-echogenic block needles.
  
  
  METHODS
  PAJUNK non-echogenic and echogenic needles were inserted into pork meat at 20°, 40°, 60°, and 70° angles, and electronic beam steering was applied at three different angles (shallow, medium, and steep) to obtain the best possible needle images. Eleven anesthesiologists blinded to the type of needle or use of beam steering scored the images obtained (0 = needle not visible; 10 = excellent needle shaft and tip visibility). Mean scores were used to classify the needles as poor visibility (mean score 0-3.3), intermediate visibility (mean score 3.4-6.6), or good visibility (mean score 6.7-10).
  
  
  RESULTS
  At 20°, the visibility scores were intermediate to good in all groups. At 40°, the mean (SD) visibility score for the non-echogenic needle improved significantly from 3.1 (1.4) to 7.9 (1.8) with application of beam steering (difference = 4.8; 95% confidence interval [CI]: 3.1 to 6.6; P < 0.001). At 60°, the mean (SD) visibility score for the non-echogenic needle was poor 0.6 (0.7) and remained poor 2.4 (1.1) with beam steering. One the other hand, the echogenic needle without beam steering 6.5 (1.8) scored significantly better than the non-echogenic needle with beam steering 2.4 (1.1) (difference = 4.2; 95% CI: 2.7 to 5.6; P < 0.001). At 70°, the mean needle visibility score was poor for the non-echogenic needle with or without beam steering. In contrast, the echogenic needle attained an intermediate visibility score with or without beam steering. Beam steering did not significantly change the visibility scores of either the echogenic or the non-echogenic needle (P = 0.088 and 0.056, respectively) at a 70° angle.
  
  
  CONCLUSIONS
  The PAJUNK echogenic needle, with or without beam steering, was more visible when compared with the non-echogenic needle at 60° and 70° angles of insertion. In contrast, at a 40° angle of needle insertion, the non-echogenic needle with beam steering was more visible compared with the echogenic needle.
authors: Department of Anesthesiology and Perioperative Medicine, London Health Sciences Centre, University of Western Ontario, 339 Windermere Road, London, ON, N6A 5A5, Canada, vishal.uppal3@gmail.com.
authors: Vishal
authors: V
authors: Uppal
authors: Rakesh V
authors: RV
authors: Sondekoppam
authors: Sugantha
authors: S
authors: Ganapathy
mesh_terms: D000776:Anesthesiology / Q000379:methods; D000818:Animals; D006801:Humans; D009339:Needles; D009407:Nerve Block / Q000295:instrumentation / Q000379:methods*; D010525:Peripheral Nerves / Q000000981:diagnostic imaging*; D013552:Swine; D018084:Ultrasonography, Interventional / Q000379:methods* / Q000639:trends