Localising an ultrasound beam travelling within the scan plane of a diagnostic ultrasound imager

A technique has been developed to localise the path of an ultrasound pulse, launched from a transmitting transducer and travelling within a scattering medium, utilising a separate receiving transducer to detect off-axis scatt ered energy. The operation of the two transducers enables a locus of the si tes of detected signals, across a range of angles, to be generated. Two dif ferent mathematical approaches were investigated for the analysis of these data, and their relative success quantified. It was found that it was possi ble to determine the parameters defining the orientation of the beam, by fi tting the data to an appropriately formed equation. A clinical application of the technique would be the visualisation of a therapeutic beam, operatin g initially at relatively low intensity, on a B-mode image. This would enab le accurate positioning of its focus in the region of interest, prior to th e application of therapeutic intensity levels and the formation of lesions. Similarly, a guidance system for the insertion of a biopsy needle into sof t tissues could be developed with this technique and a low intensity path-f inding beam. (C) 1999 Elsevier Science B.V. All rights reserved.