Figure 4. Accuracy of the tip of the needle from all subjects.

The origin represents the midline of the nerve (target). The x-axis corresponds to lateral distance, in which a positive integer means the needle is placed to the right of the target from the view of the subject. The y-axis corresponds to the depth of the needle placement, in which a negative integer means the needle is placed deeper than the target. The effective range of 5 mm is shown by the dashed circle and dashed lines.