Needle geometry effect on vibration tissue cutting

Abstract

Needle vibration tissue cutting is a method that has been shown to reduce tissue cutting force and thereby improve needle position accuracy inside the body. Needle accuracy is crucial for minimally invasive needle operations such as the radiation cancer treatment of brachytherapy. This article uniquely determines the importance of needle geometry in minimizing cutting force in needle vibration tissue cutting. This article also determines how vibration specifically affects cutting force. This new information was found by performing needle cutting experiments with five varying conical tipped needles being inserted into ex vivo bovine liver as well as a polyurethane sheet at varying vibratory amplitudes and frequencies. Results show that applying vibration to sharper needles greatly reduced the insertion force by up to 67%, where the blunter needles saw diminishing benefits. The tissue phantom experiments showed that vibration reduced the force needed to propagate the created crack but showed no improvement over the initial puncture force. This greater understanding of needle vibration tissue cutting can lead to improved needle geometry designs that work with vibration to reduce tissue cutting force.