Curving Clinical Biopsy Needles: Can We Steer Needles and Still Obtain Core Biopsy Samples?1

Needle-based procedures, such as biopsy, thermal ablation, brachytherapy, and drug delivery, provide a minimally invasive means for diagnosis or treatment. The success of the procedure relies on the needle reaching the physician’s desired target (typically identified on a medical image) accurately. However, due to tissue deformation and the accuracy limits of human hand–eye coordination, the needle may go off course. To aid in targeting, steerable needles have been developed (see, e.g., Refs. [1–3]). They offer the possibility of controllably deflecting the needle during insertion to enhance final tip accuracy, while also providing a means for obstacle avoidance (see Ref. [4] for a review). Harnessing the bending forces that arise during insertion of a bevel tipped needle is one popular way to steer needles (see, e.g., Refs. [1,5]). A fixed bend or “kinked tip” has also been employed to amplify steering [6,7]. While the kinked tip provides high curvature, when it is axially rotated (which must be done continuously to achieve a straight path), the tip cuts a locally helical track through tissue [8]. Recently, a new needle tip design that utilizes a flexure located between the needle shaft and bevel tip has been shown to provide high curvature with reduced tissue damage [8]. While the flexure-tip needle has been tested on the benchtop to evaluate curvature and tissue damage, it has yet to be incorporated into a device with either a diagnostic or interventional clinical payload. Indeed, nearly all the bevel tip steerable needle research to date, regardless of tip design, has left the incorporation of diagnostic or interventional tooling to future work. In this paper, we describe a new device that incorporates flexure-tip steering into an FDA approved commercial core biopsy needle, the Quick-Core from Cook Medical, Bloomington, IN. In addition to the use of a flexure-tip, we investigate the modification of the outer sheath of the biopsy needle to amplify steering. We show that the augmented Quick-Core can achieve appreciable curvature in tissue. We also show that the flexure-tip does not interfere with the needle’s ability to collect core biopsy samples. This work illustrates the potential of the flexure-tip to augment current clinical needles and demonstrates for the first time the delivery of a diagnostic payload in a hand-held bevel tipped steerable needle device. 2 Methods