University of Twente Student Theses


Real-time three-dimensional tracking and steering of flexible needles using two-dimensional ultrasound images

Vrooijink, G.J. (2012) Real-time three-dimensional tracking and steering of flexible needles using two-dimensional ultrasound images.

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Abstract:Needle insertion is one of the most commonly performed minimally invasive surgical procedures. Such needle insertions are often performed either for diagnosis (e.g., biopsy) or therapy (e.g., brachytherapy), both of which require accurate needle placement. Needle insertions are frequently performed under ultrasound image-guidance which provides visual feedback. Clinicians usually use rigid bevel-tipped needles that easily cut and penetrate the soft tissue. The steering capabilities of rigid bevel-tipped needles are limited. Thin and exible bevel-tipped needles offer steering capabilities which allow the needle to be steered around sensitive organs and obstacles to reach a target. Accurate steering of a exible needle in three-dimensional (3D) space is a demanding task which requires needle visualization during the insertion. In this study, real-time 3D needle tip pose feedback is obtained by a novel technique which uses a two-dimensional (2D) ultrasound transducer. The 2D transducer is positioned at the needle tip, and orientated perpendicular to the direction of needle insertion. Position measurement of the needle tip in the out-of-plane direction of the transducer cannot be obtained directly. Therefore, the transducer needs to be repositioned at the needle tip during insertion, which is done by a positioning device. The required out-of-plane motion of the transducer is determined by the needle insertion velocity which is corrected by the tip velocities. Positioning of the transducer at the needle tip allows for computation of the tip pose, which is required for needle steering. Experiments show that maximum mean errors in needle tip positions are 0.64 mm, 0.25 mm and 0.27 mm along the insertion-, horizontal- and vertical-axes, respectively. The determined needle tip orientation errors are 2.68° and 2.83° about horizontal- and vertical-axes, respectively. The needle tip pose is used in path planning in order to compute a needle trajectory to reach a desired target while avoiding an obstacle. The planner uses a customized Rapidly-exploring Random Trees (RRTs)-based path planner to determine feasible trajectories. The needle trajectory is determined by optimizing clinically motivated criteria in order to minimize tissue damage, or to maximize safety. The needle is controlled along such a trajectory by duty-cycled spinning of the needle during insertion. Experiments show needle steering with maximum targeting error of 3.5 mm (RMS) for the case with both a moving obstacle and target. Improved needle steering can be achieved by combining visualization with path planning and duty cycling, which offers the clinician an increase in targeting accuracy during minimally invasive procedures.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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