Pertains to high intensity therapeutic ultrasound (HITU) devices, specifying: - relevant parameters for quantifying the field; - measurement methods at relatively low output levels and methodology for extrapolating these to higher therapeutic level fields; - consideration of sidelobes and pre-focal maxima; - parameters relevant to HITU transducers of different construction and geometry, including non-focusing, focusing with or without lenses, collimated, diverging and convergent transducers, multi-element transducers, scanning transducers and multiple sources.