Yuki Sugano

An accurate calibration method of ultrasound images by center positions of a metal ball

This paper provides a novel method for three-dimensional tracking of ultrasound images. One of the issues to determine the position of a ultrasound image plane is the thickness of the image plane. The proposed methodology address the issue by the calibration phantom using a fiducial sphere with the diameter of 5.5 mm because comet-trail artifact can be observed in the image plane through the center of the sphere. Meanwhile, to measure the sphere center accurately by a tracking device, a pointer tool with the same sphere at the tip is also proposed. To validate the feasibility of the method, simulation and phantom tests were conducted. From the results of the phantom test, the accuracy of the calibration was 0.65, 0.40, and 0.42 mm in 10, 50, 100 points calibration. The results demonstrate that the proposed method has a great potential for accurate US probe calibration.

Image plane positioning by pneumatic actuators for ultrasound guidance

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.

Reconstruction and error detection of blood vessel network from ultrasound volume data

Recently, we described a reconstruction method of the blood vessel network by 3D thinning to detect vessels bifurcations, which is applied to the control of microbubbles in vivo. However, that method did not include error detections and was only verified on a very simply shaped artificial blood vessel. In this paper we propose a system including an abstraction method for the blood vessel network. Such a model is then analyzed through graph theory and error patterns in the reconstructed network. We proceeded in vitro by acquiring volume data from an artificial capillary with multi-bifurcations whose diameter ranges from 0.5 to 2.0mm and with different flow velocities. We were able to reconstruct the blood vessel network of an in vitro artificial capillary with multi-bifurcations. Results show that our system successfully reconstructed the corresponding networks as much as the limitation of resolution of echography.