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	Image-Based 3D Navigation of the Ultrasound Probe

	1.Background 2.Method 3.Evaluation test 4.Acknowledgment/Link Papers Takanishi Laboratory Home

1.Background

Introduction

Among all medical imaging modalities, echography examination offers various merits such as no radiation exposure, minimally invasive, low-cost． However, it is a poorly-reproducible diagnosis. A technique to solve this problem is useful for repeating inspection such as tumor observation．

Purpose

　The purpose of this study is to develop a system which can reproduce the ultrasound image of the previous diagnosis.
　Target organ in this study is liver, which observation is relatively easy compared with other abdominal organs．

2.Method

Template matching based probe guiding algorithm

　In this method uses only the B-mode image data is used. During the first examination, the sonographer obtains 3D data including the target region by scanning with a 2D probe.
　In the following examination, obtained 2D B-mode images are compared with the stored 3D data, and template-matching determines the right position of the probe.
　Since the organ is deformable, we divided the image into small parts to make up multiple templates.

Method of template matching

（1）Position detection in z axis

　The frame with the minimum D (difference of images) is the current position of the probe.

Position detection in z axis

Difference of images D

（2）Position detection in x axis

The probe’s x axis movement is defined by median of x movements of all templates
The graphical user interface guides the probe towards the right target area.

Position detection in x axis

GUI

3.Evaluation test

（1）Intrasession test

　To evaluate the effectiveness and usability of the probe navigation algorithm by sonographers
　i）Sonographer decides a target object (bifurcation of the vessel, etc)
　ii）Scan and record 3D data including the target image
　iii）Sonographer moves probe to the target area according to GUI
　iv）If the goal image contains the target object, it is counted as “success”
　Success rate was 17/18 cases.

Parameters

（2）Intersession test

　The same experiment has been carried out with minimum 10 days between 3D data recording and probe navigation
　Success rate was 2 out of 6cases. In one case the probe was close to the target but postone was wrong.

　　Click here to view the movie
　　GUI navigation

（3）Consideration

　Proposed algorithm has been validated by in-vivo experiments. Intrasession experiment shows high success rate.
　In order to increase success rate in intersession, especially guiding probe in 3 rotational axes might be required.

4.Acknowledgment/Link

　We would like to express our thanks to Prof. Saito of Tokyo Women's Medical Univ.,Prof. Sugawara of Himeji Dokkyo Univ., Prof. Niki of Tokyo City Univ. and Hitachi Aloka Medical,Ltd. for their daily suggestions and supports. And also thanks to SolidWorks Corp., for their support of CAD software.
　This study has been carried out under the permission of the Ethics Committee on Human Research　of Waseda University.

Himeji Dokkyo University

Tokyo City University

Tokyo Women's Medical University.

Hitachi Aloka Medical,Ltd.

SolidWorks Corp.

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