Kiyoshi Yoshinaka

Robotic needle insertion: effects of friction and needle geometry

Two experiments were performed to determine the effects of friction and needle geometry during robotic needle insertion into soft tissues. In Experiment I, friction forces along the instrument axis were characterized during needle insertion into bovine liver under CT fluoroscopic imaging. Because the relative velocity of the tissue and needle affect viscous and Coulomb friction, the needle insertion process was segmented into several phases of relative motion: none, partial and complete. During the complete relative motion phase, it was found that Coulomb friction accounts for the majority of needle force. In Experiment II, insertion forces along and orthogonal to the needle axis were measured during insertion into a silicone rubber phantom with a consistency similar to liver. The effects of needle diameter and tip type (bevel, cone, and triangle) on insertion force were characterized. A bevel tip causes more needle bending and is more easily affected by tissue density variations. Forces for larger diameter needles are higher due to increased cutting and friction forces. These results may be used in the control of needle insertion for robot-assisted percutaneous therapies.

The final stage of the collapse of a cloud of bubbles close to a rigid boundary.

The final stage of the collapse of a hemispherical cloud of bubbles close to a rigid boundary was investigated by ultra high-speed photography with up to 200 million frames/s. Our investigations reveal two types of secondary shock wave emission during cloud rebound. In the first case, the secondary shock wave emission is a consequence of the free collapse of a bubble within the cloud by the ambient pressure in the fluid. In the second case, it is a consequence of the interaction of the cloud-collapse-induced shock wave with microbubbles situated close to the collapse site of the cloud. The latter can be very powerful, resulting in a secondary shock wave emission with a maximum amplitude of about 0.5 GPa.

Low invasive propulsion of medical devices by traction using mucus

This paper presents a new low invasive method to drive a medical device in an organic tube. The device has a spiral ribbed impeller which converts rotation to axial motion hydrodynamically using mucus. Generated thrust and drag were estimated according to linearized hydrodynamic lubrication theory. The optimum rib shape which makes thrust force maximum is predicted theoretically. As the proposed method of driving does not require direct contact against living tissue, injury may be prevented by keeping good lubrication conditions. Principles of designing a medical device are discussed such that reliable driving is compatible with low invasive operations.

Focus Control Aided by Numerical Simulation in Heterogeneous Media for High-Intensity Focused Ultrasound Treatment

A focus control method based on time reversal aided by numerical simulation was implemented to correct focal errors in heterogeneous media by using a 56-element phased array transducer at a frequency of 2 MHz. Two types of acrylic phantom were employed to mimic the acoustic heterogeneities in the human body. Focal errors were significantly reduced by applying the phase correction. Moreover, the effects of amplitude correction, array configuration of the transducer, and transverse wave propagation in an elastic body were examined to improve the focal quality. The results suggested that the ultrasound was effectively converged on the target by correcting the amplitude of the ultrasound, and the accuracy of the focus control was enhanced by changing the array configuration and taking into account the shear elasticity of the elastic body in the simulation.

Robust kidney stone tracking for a non-invasive ultrasound theragnostic system-Servoing performance and safety enhancement-

We propose a non-invasive ultrasound theragnostic system that tracks movement in an affected area (kidney stones, in the present study) by irradiating the area with high-intensity focused ultrasound (HIFU). In the present paper, the concept behind a novel medical support system that integrates therapy and diagnostics (theragnostics) is illustrated. The required functions for the proposed system are discussed and an overview of the constructed system configuration is illustrated. The problems associated with kidney stone motion tracking by ultrasonography are described. In order to overcome these problems, we consider two approaches. The first approach is to minimize the servoing error so as to enhance both the efficiency of the therapy and the safety of the patient. The second approach is to reduce the effect of the servoing error. With respect to the first approach, we propose a robust detection method of the stone position based on shape information. With respect to the second approach, we propose a solution for controlling the HIFU irradiation power in accordance with the servoing error, primarily in order to enhance the safety of the patient.

A control framework for the non-invasive ultrasound theragnostic system

The non-invasive ultrasound theragnostic system, we propose, tracks and follows movement in an affected area —kidney stones here—, while High-Intensity Focused Ultrasound (HIFU) is irradiated onto the area. In this paper, the concept of the novel medical support system, which integrates the therapy and diagnostics, is illustrated at first. Secondly, structuring the required functions for the proposed system is discussed. Third, the overview of the constructed system configuration is illustrated. Fourth, the problem of the stone motion tracking by ultrasonography is clarified. To cope with this problem, the respiratory motion of a human kidney is analyzed and a controller, by utilizing the quasi-periodical motion of the respiratory kidney motion, is proposed. Finally, the result of the servoing and HIFU irradiation experiments of the model stone, which moves based on the real human kidney motion data, is reported to confirm the effectiveness of the proposed controller and the constructed system.

Visual servoing for a US-guided therapeutic HIFU system by coagulated lesion tracking: a phantom study.

Applying ultrasound (US)‐guided high‐intensity focused ultrasound (HIFU) therapy for kidney tumours is currently very difficult, due to the unclearly observed tumour area and renal motion induced by human respiration. In this research, we propose new methods by which to track the indistinct tumour area and to compensate the respiratory tumour motion for US‐guided HIFU treatment.

Feed-Forward Controller for the Integrated Non-Invasive Ultrasound Diagnosis and Treatment

The integrated non-invasive ultrasound diagnosis andtreatment we propose tracks and follows movementin an affected area –kidney stones here– while High-Intensity Focused Ultrasound (HIFU) is irradiatedonto the area. High-speed CCD camera cannot beused in non-invasive diagnosis and treatment becausewe must avoid damaging healthy tissue. Servoing er-ror mainly due to ultrasound imaging and its deadtime become serious problems, unlike when a high-speed camera is used. We propose feed-forward con-trol using semi-regular kidney movement focusing onenhancing servoing performance.Keywords: non-invasive ultrasound diagnosis and treat-ment, motion tracking, feed-forward control, High Inten-sity Focused Ultrasound, medicalsupport system

A Novel High Intensity Focused Ultrasound Robotic System for Breast Cancer Treatment

High intensity focused ultrasound (HIFU) is a promising technique for cancer treatment owing to its minimal invasiveness and safety. However, skin burn, long treatment time and incomplete ablation are main shortcomings of this method. This paper presents a novel HIFU robotic system for breast cancer treatment. The robot has 4 rotational degrees of freedom with the workspace located in a water tank for HIFU beam imaging and ablation treatment. The HIFU transducer combined with a diagnostic 2D linear ultrasound probe is mounted on the robot end-effector, which is rotated around the HIFU focus when ablating the tumor. HIFU beams are visualized by the 2D probe using beam imaging. Skin burn can be prevented or alleviated by avoiding long time insonification towards the same skin area. The time cost could be significantly reduced, as there is no need to interrupt the ablation procedure for cooling the skin. In addition, our proposed robot control strategies can avoid incomplete ablation. Experiments were carried out and the results showed the effectiveness of our proposed system.

A Framework of the Non-invasive Ultrasound Theragnostic System

The authors have developed an Non-Invasive Ultrasound Theragnostic System to decrease the strain of patients and medical doctors. The system we propose tracks and follows movement in an affected area ---kidney stones here--- while High-Intensity Focused Ultrasound (HIFU) is irradiated onto the area. In this paper, a framework of the non-invasive ultrasound theragnostic system is proposed and illustrated. Specifically, the concept of the system is proposed at first. Secondly, decomposing and reconstructing (structuring) of the functional requirements are discussed. Third, the constructed system, which is based on those structured functional requirements, is illustrated. Fourth, the result of the servoing experiments of the model stone is reported to confirm the effectiveness of the proposed construction methodology and constructed system.