Table 1 Needle design specifications.

DOF

Rotational degrees of freedom

1

2

d_sheath

Sheath diameter (mm)

2.60

–

d_cannula

Cannula diameter (mm)

1.65

1.80

d_stylet

Stylet diameter (mm)

1.30

1.30

EI_stylet

Stylet flexural rigidity (10^–3 N m²)

6.8

6.1

EI_joint

Joint flexural rigidity (10^–3 N m²)

6.6

2.4

–

Hydrophilic sheath

✓

–

–

Echogenic tip

✓

✓