  It has been recently demonstrated that use of ultrasound increases the tissue
yield in ultrasound-enhanced fine-needle aspiration biopsy (USeFNAB) as
compared to conventional fine-needle aspiration biopsy (FNAB). To date, the
association between bevel geometry and needle tip action has not been widely
explored. In this study, we studied the needle resonance characteristics and
deflection magnitude of various needle bevel geometries with varying bevel
lengths. With a conventional lancet, having a 3.9 mm long bevel, the tip
deflection efficiency in air and water was 220 and 105 micrometres per Watt,
respectively. This was higher in comparison to an axi-symmetric tip, having a
bevel length of 4 mm, which achieved a deflection efficiency of 180 and 80
micrometres per Watt in air and water, respectively. This study emphasised the
importance of relationship between flexural modulus of bevel geometry in the
context of various insertion media and, thus, could provide understanding on
approaches to control post-puncture cutting action by modifying the needle
bevel geometry, essential for the USeFNAB application.
