Ultrasound probe tilt impedes the needle-beam alignment during the ultrasound-guided procedures.

The objective of this study was to identify the factors that complicate the needle visualization in ultrasound-guided in-plane needling procedures. Forty-nine residents were recruited and randomized to insert the simulated blood vessel with four different views including Neutral (the long axis of the probe along the visual axis and the ultrasonic beam vertical to the surface of gel phantom), 45°-rotation (45° angle between the long axis of probe and the operator's visual axis), 45°-tilt (45° angle between the ultrasonic beam and the surface of gel phantom) and 45°-rotation plus 45°-tilt of probe. Number of needle redirections, insertion time, and needle visibility were documented and compared for each procedure. When the residents faced with 45°-tilt view, the needle redirections (2 vs 0) and insertion time increased significantly (39 vs 16) compared with that of the Neutral view. When faced with 45°-rotation plus 45°-tilt view, the residents' performance decreased further as compared with that of the 45°-tilt view and the Neutral view. However, there was no performance difference between the Neutral view and 45°-rotation view. In conclusion, during ultrasound-guided in-plane procedures, tilting the ultrasound probe may increase the difficulty of needle-beam alignment.