Effect of skin thickness on target motion during needle insertion into soft-tissue phantoms

Small breast lesions are increasingly detected by medical imaging modalities. However, a biopsy of the lesion is required to make a definitive diagnosis. During the biopsy, displacement of the target (lesion) occurs as the needle indents and punctures the skin layer, and penetrates further into the breast soft tissue. Target displacement during the needle insertion process makes it difficult to reach the lesion. In this study, the elastic properties of a soft-tissue phantom were estimated, and the effects of skin thickness on target motion and insertion force during needle insertion were investigated. The elastic properties of the target, skin, and the surrounding tissue were estimated in vivo using an ultrasound-based approach which uses Acoustic Radiation Force Impulse technique to determine the elastic moduli of tissue. Ultrasound images were used to track target motion during needle insertion into soft-tissue phantoms. Target displacement was computed using digital image correlation. The experimental results show that the insertion force rate increases by 90.2% and the rate of target displacement increases by 275.9%, when the skin thickness is increased from 0 mm to 2.5 mm. Studying the effect of skin thickness on the target motion during needle insertion will help in pre-operative planning and thus, improve the clinical outcomes of the biopsy procedure.