Ultrasound-guided three-dimensional needle steering in biological tissue with curved surfaces

Abstract

In this paper, we present a system capable of automatically steering a bevel-tipped flexible needle under ultrasound guidance toward a physical target while avoiding a physical obstacle embedded in gelatin phantoms and biological tissue with curved surfaces. An ultrasound pre-operative scan is performed for three-dimensional (3D) target localization and shape reconstruction. A controller based on implicit force control is developed to align the transducer with curved surfaces to assure the maximum contact area, and thus obtain an image of sufficient quality. We experimentally investigate the effect of needle insertion system parameters such as insertion speed, needle diameter and bevel angle on target motion to adjust the parameters that minimize the target motion during insertion. A fast sampling-based path planner is used to compute and periodically update a feasible path to the target that avoids obstacles. We present experimental results for target reconstruction and needle insertion procedures in gelatin-based phantoms and biological tissue. Mean targeting errors of 1.46±0.37 mm, 1.29±0.29 mm and 1.82±0.58 mm are obtained for phantoms with inclined, curved and combined (inclined and curved) surfaces, respectively, for insertion distance of 86-103 mm. The achieved targeting errors suggest that our approach is sufficient for targeting lesions of 3mm radius that can be detected using clinical ultrasound imaging systems.

Keywords: Computer-assisted surgery; Minimally invasive procedures; Needle steering; Ultrasound.

Fig. 1

The experimental setup used for needle insertion into a soft-tissue phantom that includes biological tissue (chicken breast tissue) with a curved surface. The inset shows an ultrasound transducer moving over a curved surface.

Fig. 2

Ultrasound transducer positioning device with a 2 degrees-of-freedom rotational mechanism. The positioning device provides movements in x-, y- and z-axis and the rotation mechanism allows for pitch (θ) and roll (ϕ) movements. The force/torque sensor is attached to the rotational mechanism to measure the contact force (f_c) and the torque (t_x) round the x-axis. The geometry of the curved phantom consists of different inclination angles. The dimensions of the cuboidal flat phantom are 230 mm × 148 mm × 48 mm.

Fig. 3

Target localization and reconstruction. (a) The image is inverted and the contrast is enhanced by transforming the values using contrast-limited adaptive histogram equalization. (b) The image is converted to a binary image based on threshold. (c) Small pixel groups are removed and the image is morphologically closed resulting in the final segmented image. (d) The binary images are staked together based on the position and orientation of the probe while acquiring each image frame. (e) The centroid of the target volume is calculated using all image frames that include the target. (f) The target surface is reconstructed using the contour points of the segmented images.

Fig. 4

Effect of system parameters (Table 1) on the absolute displacement of the target during needle insertion. (a) Needle insertion speed and bevel angle. (b) Skin thickness and needle diameter. (c) Target size and target distance.

Fig. 5

Experimental cases. The steering algorithm controls the needle to avoid an obstacle reach a 3 mm radius target in a soft tissue phantom. (a) Case 1: the phantom is placed on an inclined surface. (b) Case 2: the phantom has an curved surface. (c) Case 3: the target is embedded in biological tissue. The biological tissue is embedded into a curved gelatin phantom placed on an inclined surface.