Design of an ultrasonic physiotherapy system with pulse wave feedback control.

<bold>Background: </bold>Due to different physical and biological mechanisms behind ultrasound hyperthermia and phonophoresis, the requirement for ultrasound power, frequency and control modes varies.<bold>Objective: </bold>This paper introduces an adaptive ultrasonic physiotherapy system based on real-time surveillance over physiological characteristics of the patients, which in turn assists the individual treatment and dose limitation in auxiliary rehabilitation.<bold>Methods: </bold>The method essentially takes advantage of distinctive characteristics of two different phases (systole and diastole) of the human cardiac cycle as a medium for modulation. The abundance of blood flow during systole enables energy exchange for hyperthermia while blood flow insufficiency caused by diastole assists in drug penetration. Said method could improve the adjuvant therapy as it provides partial drug penetration and therapeutic dosage control.<bold>Results: </bold>By adjusting time window and intensity of multi-frequency ultrasound, it is possible to reduce the irradiation dosage to around 22% of that during continuous irradiation at 1 MHz. The method shows high potential in clinical practice.<bold>Conclusion: </bold>Frequency-tuning ultrasound therapy would be more efficient regarding drug penetration and improve the therapeutic efficacy of hyperthermia. [ABSTRACT FROM AUTHOR]