Norihiro Koizumi

Ultrasound image based visual servoing for moving target ablation by high intensity focused ultrasound: US image based visual servoing for moving target ablation by HIFU

Although high intensity focused ultrasound (HIFU) is a promising technology for tumor treatment, a moving abdominal target is still a challenge in current HIFU systems. In particular, respiratory‐induced organ motion can reduce the treatment efficiency and negatively influence the treatment result. In this research, we present: (1) a methodology for integration of ultrasound (US) image based visual servoing in a HIFU system; and (2) the experimental results obtained using the developed system.

A new device for fiducial registration of image-guided navigation system for liver RFA

PurposeRadiofrequency ablation for liver tumors (liver RFA) is widely performed under ultrasound guidance. However, discriminating between the tumor and the needle is often difficult because of cavitation caused by RFA-induced coagulation. An unclear ultrasound image can lead to complications and tumor residue. Therefore, image-guided navigation systems based on fiducial registration have been developed. Fiducial points are usually set on a patient’s skin. But the use of internal fiducial points can improve the accuracy of navigation. In this study, a new device is introduced to use internal fiducial points using 2D US.Methods3D Slicer as the navigation software, Polaris Vicra as the position sensor, and two target tumors in a 3D abdominal phantom as puncture targets were used. Also, a new device that makes it possible to obtain tracking coordinates in the body was invented. First, two-dimensional reslice images from the CT images using 3D Slicer were built. A virtual needle was displayed on the two-dimensional reslice image, reflecting the movement of the actual needle after fiducial registration. A phantom experiment using three sets of fiducial point configurations: one conventional case using only surface points, and two cases in which the center of the target tumor was selected as a fiducial point was performed. For each configuration, one surgeon punctured each target tumor ten times under guidance from the 3D Slicer display. Finally, a statistical analysis examining the puncture error was performed.ResultsThe puncture error for each target tumor decreased significantly when the center of the target tumor was included as one of the fiducial points, compared with when only surface points were used.ConclusionThis study introduces a new device to use internal fiducial points and suggests that the accuracy of image-guided navigation systems for liver RFA can be improved by using the new device.

An automatic templates selection method for ultrasound guided tumor tracking

In this report, we propose a novel robust tumor tracking method for ultrasound guided RFA (radiofrequency ablation) treatments. Organ deformations seriously deteriorate the tracking performance. To cope with this problem, we propose a novel motion tracking method using dynamic templates. Our method achieves stable tracking by selecting templates automatically based on the texture features of ultrasound diagnostic images. On the other hand, the conventional method is unstable due to the variation to select templates manually. Experimental results show the effectiveness of our proposing motion tracking method concerning the robustness and accuracy.

A study for tracking focal lesions in non-invasive ultrasound theragnostic system

In recent years, HIFU (High Intensity Focused Ultrasound) therapy, which is one of the non-invasive therapies utilizing focused ultrasound, have attracted a great attention as a novel treatment method for a focal lesion, such as a tumor and a stone. However, the focal lesion moves in accordance with respiration, which may cause the damage for the surrounding normal tissues. To cope with this problem, we have developed a non-invasive ultrasound theragnostic system (NIUTS). In this report, we propose a novel tracking method, which is implemented in NIUTS, based on “Partial Active Shape Model” to enhance the servo performance for the focal lesion. Experimental results shows the effectiveness of the proposed servo method concerning the precision and robustness for a kidney phantom.