Akinori Onishi

Development of an integrated needle insertion system with image guidance and deformation simulation

OBJECTIVE The purpose of our work was to develop an integrated system with image guidance and deformation simulation for the purpose of accurate needle insertion. METHODS We designed an ultrasound-guided needle insertion manipulator and physical model to simulate liver deformation. We carried out an in vivo experiment using a porcine liver to verify the effectiveness of our manipulator and model. RESULTS The results of the in vivo experiment showed that the needle insertion manipulator accurately positions the needle tip into the target. The experimental results also showed that the liver model accurately reproduces the nonlinear increase of force upon the needle during insertion. DISCUSSION Based on these results, it is suggested that the needle insertion manipulator and the physical liver model developed and validated in this work are effective for accurate needle insertion.

Deformation simulation using a viscoelastic and nonlinear Organ model for control of a needle insertion manipulator

This paper shows the viscoelastic and nonlinear organ deformation model for organ model-based control of needle insertion, in which the deformation of an organ is calculated intraoperatively and the needle is manipulated with organ deformation taken into consideration. An organ model including such detailed material characteristics is important to achieve the control method in question. Firstly, the material properties of the liver are modeled from the measured data and its viscoelastic characteristics are represented by differential equations, including the term of the fractional derivative. Nonlinearity in terms of the fractional derivative was measured, and modeled using the quadratic function of strain. Next, a solution of an FE model using such material properties is shown. We use sampling time scaling property as the solution for the viscoelastic system. The solution for a nonlinear system using the Modified Newton-Raphson method is also shown. Finally, the organ deformation, assuming the needle is inserted, is simulated using an organ model and the overall deformation and distribution of the strain is computed in these simulations.

In vitro validation of viscoelastic and nonlinear physical model of liver for needle insertion simulation

Needle insertion treatments require accurate placement of the needle tip into the target cancer. However, it is difficult to insert the needle into the cancer because of cancer displacement due to the organ deformation. Then, a path planning using numerical simulation to analyze the deformation of the organ is important for the accurate needle insertion. The objective of our work is to develop and validate a viscoelastic and nonlinear physical liver model. First, an overview is given of the development of the physical liver model. Second, the experimental method to validate the model is explained. In-vitro experiments that made use of a pigpsilas liver were conducted for comparison with the simulation using the model. Results of the in-vitro experiment showed that the liver model reproduces (1) the relationship between needle displacement and force during needle insertion; (2) velocity dependence of needle displacement and force when a puncture occurs; and (3) nonlinear and viscoelastic response of displacement at an internally located point displacement, with high accuracy.

Viscoelastic and Nonlinear Organ Model for Control of Needle Insertion Manipulator

This paper shows the viscoelastic and nonlinear organ deformation model for organ model-based control of needle insertion, in which the deformation of an organ is calculated intraoperatively and the needle is manipulated with organ deformation taken into consideration. An organ model including such detailed material characteristics is important to achieve the control method in question. Firstly, the material properties of the liver are modeled from the measured data and its viscoelastic characteristics are represented by differential equations, including the term of the fractional derivative. Nonlinearity in terms of the fractional derivative was measured, and modeled using the quadratic function of strain. Next, a solution of an FE model using such material properties is shown. We use sampling time scaling property as the solution for the viscoelastic system. The solution for a nonlinear system using the Modified Newton-Raphson method is also shown. Finally, the organ deformation, assuming the needle is inserted, is simulated using an organ model and the overall deformation and distribution of the strain at each element is computed in these simulations.

Developing a planning method for straight needle insertion using probability-based condition where a puncture occurs

Needle insertion treatments require accurate placement of the needle tip into the target cancer. However, it is difficult to insert the needle accurately because of cancer displacement caused by organ deformation. Therefore, a path planning using numerical simulation to analyze the deformation of the organ is important for accurate needle insertion. The problem in developing a planning method is that puncture conditions, such as the force applied to the needle, is difficult to be decided deterministically, because the experimental data of puncture conditions have variations. Therefore, the purpose of this research was to develop a novel planning method to decide the robust paths of straight needle insertion for various puncture points. The basic idea of this planning method is to consider the puncture condition probabilistic and to evaluate the expected value of needle placement accuracy. First, a probability-based puncture condition was introduced, and then the expected value of needle placement accuracy was defined. Next, the optimization method was developed to search the insertion path in a way that minimizes the expected values of needle placement accuracy. Then, a numerical simulation and evaluation of the planning method was conducted, using a liver-shaped 2D model. Furthermore, an in-vitro experiment was carried out to measure needle placement accuracy from the optimized path. Experimental results show that the planning method realizes needle insertion with a mean accuracy of 1.5 mm.

Modeling of conditions where a puncture occurs during needle insertion considering probability distribution

Needle insertion treatments require accurate placement of the needle tip into the target cancer. However, it is difficult to insert the needle into the cancer because of cancer displacement due to the organ deformation. Then, a path planning using numerical simulation to analyze the deformation of the organ and the timing of puncture is important for the accurate needle insertion. In this study, we have explained the modeling of conditions where the puncture occurs. Firstly, this paper shows needle insertion experiments for the hog liver in order to measure the needle force and displacement where the puncture occurs. According to the experimental results, significant variations in puncture force were observed. Accordingly, we proposed a novel condition of the force causing a puncture considering probability distribution. We summarized variations of the puncture force in the experimental data and represented conditions where a puncture occurs with probability distribution models where the force is random variable. In addition, the boundary conditions and liver shapes are considered by analyzing the stress status near the needle. Then, we derived the conditions of the puncture with probability distribution models where the stress is random variable.

Validation of Viscoelastic and Nonlinear Liver Model for Needle Insertion from in Vivo Experiments

This paper shows the viscoelastic and nonlinear liver model for organ model based needle insertion, in which the deformation of an organ is estimated and predicted, and the needle trajectory is decided with organ deformation taken into consideration. An organ model including detailed material characteristics is important in order to achieve the proposed method. Firstly, the material properties of the liver are modeled from the measured data and its viscoelastic characteristics are represented by differential equations, including the term of the fractional derivative. Nonlinearity in terms of the stiffness was measured, and modeled using the quadratic function of strain. Next, a solution of an FE(Finite element) model using such material properties is shown. We use the sampling time scaling property as the solution for the viscoelastic system, while the solution for a nonlinear system using the Euler method and the Modified Newton-Raphson method is also shown. Finally, the deformation of liver model is calculated and pig liver of in vivo situation is obtained from medical ultrasound equipment. Comparing the relationship between needle displacement and force on real liver and liver model, we validate the proposed model.

Developing a method to plan robotic straight needle insertion using a probability-based assessment of puncture occurrence

Needle-based treatments for cancer require accurate placement of the needle tip into the target tissue. However, it is often difficult to insert a needle accurately because of the cancer displacement caused by organ deformation. Therefore, developing a planning method based on a numerical simulation that analyzes organ deformation is important for accurate needle insertion. However, predicting the puncture conditions, including the force applied to the needle is not trivial owing to marked variations in the experimental data. The purpose of this research is to develop a novel method for predicting a robust path for straight needle insertion with various puncture points. The method is based on the probabilities of the various puncture conditions and evaluates the expected accuracy of needle placement. First, a probability-based puncture condition was established and the expected accuracy of needle placement was defined. We also performed in vitro needle insertion experiments using a porcine liver. Significant variations in puncture force were observed. Accordingly, we established a probability distribution for the tissue stress caused by the puncture. An in vitro experiment was performed to measure needle placement accuracy using the optimized path. Experimental results show that the proposed method achieves a mean accuracy of 1.5 mm.