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Therapeutic use of ultrasound (US) has a great potential for minimally invasive therapy. We have studied acoustic microbubble delivery for effective sonoporation and thermal therapy. To apply the techniques in vivo, a navigation system for US field positioning is indispensable. To address this issue, we have developed an intuitive navigation system using augmented reality (AR) technology. The system consists of an optical tracking device, a linear US probe, a focused US field source (US transducer) with 2.0-mm focal spot, a USB video camera, and navigation software. The probe was calibrated accurately using US probe calibration technique. Also, the transducer was calibrated using a three-dimensional sound field measurement device. Finally, the camera was calibrated using a chess board. The system we developed provides two kinds of augmented information : 1) therapeutic US field visualization on echogram, and 2) echogram plane and sound field visualization on video frame. In this study, the respective calibration accuracies were validated and microbubble trapping experiments using the focused US transducer and artificial blood vessel with 2.0-mm diameter were conducted. In the experiments, microbubbles were trapped inside the artificial blood vessel using the navigation system, implying that the focus position could be located in the blood vessel. The results demonstrated that the system we developed has adequate accuracy for microbubble control in 2.0-mm blood vessels.

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Image guided procedures such as percutaneous needle insertion or high intensity focused ultrasound, have become quite widespread. In images acquisition, ultrasound (US) is convenient to use in a conventional operating room, and inexpensive compared to CT and MRI. However, US requires to handle an US probe and do not have the base coordinate system. Therefore, intraoperative image position is unclear and cannot position to interested area. To address the issues, we have developed a robotic system based on US calibration and a probe scanning robot. In this study, to validate the implement system, positioning accuracy of an image plane was evaluated. Moreover, we developed an automated US guidance system with a conventional US probe. The system enables image plane positioning to visualize a therapeutic tool automatically. From the results, positioning accuracy of the image plane was 1.6 mm and 1.5 deg, maximally. In the phantom test, the error between the positions of the image plane and the mock needle was 2.5 mm and 0.9 deg. We have confirmed that the proposed system is greatly applicable for an intraoperative US guidance.

Pneumatic actuator is low-weight, high-power and has backdrivability. In applications of the field of medicine, mechanisms using pneumatic actuators are studied for images acquisition. In images acquisition, ultrasound is non-invasive and enables to present the relative position between a therapeutic tool and organ etc. to physician in quasi-real-time. However, an ultrasound probe has individual specificity. Therefore, the relative position between the probe and an echogram was unclear and acquiring optional images of target object was difficult. Thus, we address the problem by 3-D image plane positioning method. In this study, we develop a probe scan mechanism for echography using pneumatic actuators and evaluate that basic performance of a position control accuracy of an image plane.