Regional Anesthesia Concepts
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Strategies
Needle-beam angle
The angle at which the needle shaft and US beam intersect (needle-beam angle) greatly affects needle visibility (Fig 3). The smooth metallic surface of a standard needle is a specular (mirror-like) reflector of US waves, hence a greater number of echoes will return to the transducer as the needle-beam angle approaches 90°.36 B.D. Sites, R. Brull, V.W. Chan, B.C. Spence, J. Gallagher, M.L. Beach, V.R. Sites and G.S. Hartman, Artifacts and pitfall errors associated with ultrasound-guided regional anesthesia Part I: Understanding the basic principles of ultrasound physics and machine operations, Reg Anesth Pain Med 32 (2007), pp. 412418. Article | PDF (1295 K) | View Record in Scopus | Cited By in Scopus (3)36 As a result, in plane needle tip and shaft visibility is better at larger needle-beam angles;[10], [13], [14], [16] and [17] the optimal angle appears to be >55°.[10], [16] and [17] Interestingly, out of plane needle tip visibility is better at smaller needle-beam angles (≤30°); however, the reason for this is not clear.[17] and [18]
