Fig. 3

Schematic shows the possible technique options for returning the needle into the ultrasound plane in the LAX-IP approach when the needle leaves the plane as it advances. c and d may be more suitable for pediatric settings because the ultrasound plane does not move away from the “best plane.” a The needle is on the ultrasound plane. b The probe is slightly rotated toward the catheter. c The catheter is slightly moved toward the center line of the probe. d The catheter is withdrawn to the near skin, and the procedure is restarted. Side-lobe and slice-thickness are possible explanations for cases when the catheter appears to be placed successfully into the vessel in the LAX-IP approach, but no back flow is observed in the catheter hub. The two artifacts are very similar [40]. e When a strong reflector occurs in the side-lobe beam, the ultrasound machine mixes the reflected signals of the main and side-lobe beam, and structures these signals into the same ultrasound image (side-lobe artifact). f The ultrasound machine assumes that the emitted beam is extremely thin. However, the beam actually has a measurable thickness that varies with depth. Thus, when the needle and the vessel are in the same beam width, even if the needle is not inserted into the vessel, they are structured into the same ultrasound image (slice-thickness artifact)