An experimental study of force field control under water using acoustic holography for ultrasound therapy

Abstract

Low-intensity pulsed ultrasound (LIPUS) is commonly used for bone fracture healing to mechanically stimulate a fracture site and accelerate the repair process. Recent studies reported that LIPUS stimulation could have various effectiveness such as not only fracture healing but also regenerative medicine of articular cartilage and cognitive dysfunction improvement. However, conventional LIPUS devices stimulate both affected and unaffected sites. To promote healing effects at an affected site and enhance therapeutic applications, LIPUS devices should employ acoustic holography, which can control force fields and provide the desired ones to an affected site. However, conventional control algorisms cannot form desired force fields and have not been used in vivo for therapy. In this study, we experimentally investigate the feasibility to control force fields by acoustic holography using an ultrasound transducer array under water for therapy. First, we designed and prototyped a simple device for generating force fields using a 4×4 ultrasound transducer array under water for therapy. Then, we introduced a force field control algorithm developed in our previous study into the prototype force field generator to experimentally verify the controllability to achieve desired force fields for therapy. The findings show that the prototype force field generator meets acoustic intensity enough for fracture healing by focused ultrasound and that the developed control algorism applied to the prototype force field generator forms a two-dimensional force field similar to a rectangular shape assuming a fracture line as a target area and suppresses the acoustic intensity outside the target area.

Keywords

• ultrasound therapy
• low-intensity pulsed ultrasound
• acoustic holography
• ultrasound transducer array
• bone fracture healing
• force field