Katsuhiko Fujimoto

Method and apparatus for ultrasonic wave medical treatment using computed tomography

An ultrasonic wave medical treatment in which the position of the focal point of the ultrasonic waves, the temperature in a vicinity of the object to be treated, and the effect of the treatment can be determined easily and accurately. The three-dimensional image information of the object to be treated obtained by a computed tomography device is utilized in locating the focal point. In case of using a nuclear magnetic resonance imaging device as the computed tomography device, the T2 weighted image and the chemical shift data can be used in checking the effect of the treatment and the temperature in a vicinity of the object. The endocavitary probe equipped with temperature and intensity sensors may also be used. The ultrasound tomographic images obtained by the ultrasound tomographic imaging device may also be used in conjunction with the three-dimensional image information. Sequential shifting of the focal point of the ultrasonic waves may be employed to reduce adverse influence due to the cavitation.

A new cavitation suppression technique for local ablation using high-intensity focused ultrasound

When soft tissues are coagulated instantaneously during a high temperature local heating therapy for cancer using high-intensity focused ultrasound, it is extremely important to have good control over the heated area. However, scattering of the ultrasonic energy by cavitation bubbles generated by sonication degrades the heating performance at the focal spot, and there is an undesirable rise in temperature along the ultrasonic path due to the absorption of ultrasonic energy. To overcome this problem, the authors developed a new method called Cavitation Suppression Technique (CAST) to promote cavitation collapse and remove gas bubbles by sweeping the driving frequency rapidly. In this study, best conditions for CAST were obtained by comparing the effect of cavitation suppression on various driving parameters. The cavitation suppression effect and control of the heating due to field overlap (near-field heating) during focus scanning were confirmed in in vitro and in vivo experiments.

Navigation of High Intensity Focused Ultrasound Applicator with an Integrated Three-Dimensional Ultrasound Imaging System

A three-dimensional ultrasound imaging system was integrated in a HIFU applicator. This makes it easy to register the focal position of the HIFU applicator in the obtained three-dimensional volume data by three-dimensional ultrasound imaging system. The applicator was mounted on a mechanical manipulator with three degrees of freedom. The HIFU probe was positioned according to the volume data of the tissue around the target obtained by the ultrasound imaging system. A phantom study was conducted to evaluate the accuracy of navigation. Navigation errors were within 3 mm. It could also detect the monitor the change in acoustic properties of tissue due to HIFU application. The system uses history of HIFU application during therapy can be recorded in the system to assist appropriate manipulation of the probe by surgeons. The developed system is a simple, a cost-effective, and compact device for minimally invasive liver surgery.