Uniform pulsed fields for ultrasonic bioeffect experimentation

The rationale and methods are presented for producing high amplitudes of pulsed ultrasound distributed uniformly over several square centimetres. Pulsed fields (p = 1 MPa, 1-9 pulses per burst, up to 10(4) bursts per second, pulse-average intensity up to 39 W cm-2, centre frequencies 1, 2.5 and 3.5 MHz) were produced using high power pulsers and minimally damped 3.8 cm diameter transducers. Wave-forms and negative pressure distributions in water are displayed for these transducers. The lateral distributions of pressure amplitudes were uniform within +/- 15% over areas up to 4 cm2. These fields are suitable for use in bioeffect experiments to investigate possible health hazards of diagnostic pulsed ultrasound, as well as for possible therapeutic applications.