Pulsed Ultrasonic Fields

Numeric Methods and Measurements

Abstract

This report is a summary of the medical ultrasound activity at Oslomet over several years. The modelling of pulsed field propagation and generation is based on the method of the spatial impulse response method. A novel numeric algorithm for calculating the spatial impulse response has been developed and tested. The novel algorithm uses weighted binning to reduce the numeric noise in the calculation and the computation time can therefore be reduced. The method can be used for any source function. The method has been tested by comparison to piecewise analytic solutions and measurements. The measurements have been done in a water tank with several transducers as sources. Some of the transducer’s impulse responses were modified by digital inverse filtering. Measurements of pulse responses and beam profiles have verified the calculation method. Measurements of harmonic generation and propagation has been demonstrated, showing a narrower beam profile. Depth resolution was measured by applying deconvolution and the theoretical minimum of one-half period was achieved.