Low frequency ultrasounds in medicine

Ultrasound energy at frequency lower than 200 kHz has been used recently in medical field for transdermal drug transport and therapy with experimental results better than high frequency ultrasound at few MHz. As a consequence, the low frequency ultrasounds are gained more interest in the medical field. In the paper we review the most promising application of low frequency ultrasounds with emphasis on technology transducers and measurements. Furthermore, we propose a piezopolymer transducer, originally aimed to emulate the bat bio-sonar, that has low acoustic impedance to match biological tissue. It is light, small and low cost and could be used for medical application.