Modeling of flexible needle insertion in moving tissue

Ankara : The Department of Computer Engineering and the Graduate School of Engineering and Science of Bilkent University, 2012.Thesis (Master's) -- Bilkent University, 2012.Includes bibliographical references.Steerable needles can be used for minimally invasive surgeries to reach clinical targets which were previously inaccessible by rigid needles. Using such flexible needles to plan an insertion for these procedures is difficult because of the nonholonomic motion of the bevel-tip needles and the presence of anatomical obstacles. In this work, we take into consideration another property of such procedures being the tissue motion as well as these. For instance in a minimally invasive cardiac surgery one should take into account the effect of the heart’s beating motion on the needle during its insertion or in any other procedure the effect of human breathing. In this thesis, we develop a motion model for a bevel-tip needle such that it can be inserted within in any tissue under a motion which can be characterized by a time-dependent diffeomorphism. We then explore motion planning under periodic motion of a homogeneous, planar tissue where we use the Rapidly-exploring Random Trees (RRTs) method with the developed model to explore the tissue. While we perform the planning, we aim that the needle reaches a target area in the tissue while avoiding obstacles which are actually tissue segments that we want to avoid getting in contact with and intuitively follow the same motion of the tissue.Güven, Aslı DenizM.S

Closed-Loop Planning and Control of Steerable Medical Needles

Steerable needles have the potential to increase the effectiveness of needle-based clinical procedures such as biopsy, drug delivery, and radioactive seed implantation for cancer treatment. These needles can trace curved paths when inserted into tissue, thereby increasing maneuverability and targeting accuracy while reaching previously inaccessible targets that are behind sensitive or impenetrable anatomical regions. Guiding these flexible needles along an intended path requires continuously inserting and twisting the needle at its base, which is not intuitive for a human operator. In addition, the needle often deviates from its intended trajectory due to factors such as tissue deformation, needle-tissue interaction, noisy actuation and sensing, modeling errors, and involuntary patient motions. These challenges can be addressed with the assistance of robotic systems that automatically compensate for these perturbations by performing motion planning and feedback control of the needle in a closed-loop fashion under sensory feedback. We present two approaches for efficient closed-loop guidance of steerable needles to targets within clinically acceptable accuracy while safely avoiding sensitive or impenetrable anatomical structures. The first approach uses a fast motion planning algorithm that unifies planning and control by continuously replanning, enabling correction for perturbations as they occur. We evaluate our method using a needle steering system in phantom and ex vivo animal tissues. The second approach integrates motion planning and feedback control of steerable needles in highly deformable environments. We demonstrate that this approach significantly improves the probability of success compared to prior approaches that either consider uncertainty or deformations but not both simultaneously. We also propose a data-driven method to estimate parameters of stochastic models of steerable needle motion. These models can be used to create realistic medical simulators for clinicians wanting to train for steerable needle procedures and to improve the effectiveness of existing planning and control methods. This dissertation advances the state of the art in planning and control of steerable needles and is an important step towards realizing needle steering in clinical practice. The methods developed in this dissertation also generalize to important applications beyond medical needle steering, such as manipulating deformable objects and control of mobile robots.Doctor of Philosoph