Waveform index evaluation using an electronic injection phantom

A portable all electronic Doppler phantom is described. Use of a commercially obtainable wide-band audio phase shifting board allows the injection of realistic waveforms, a facility allowing novel quality assurance techniques such as the accuracy of waveform index calculation packages to be assessed. The use of this phantom results in exceptionally high sideband suppression and a highly linear power spectral density injection characteristic at a discrete number of scanner operating frequencies in the range of 2-10 MHz. The Edinburgh ESI phantom can also inject any of 12 internally generated discrete simulated Doppler shift audio frequencies for fast testing of the Doppler frequency mapping operation of ultrasonic scanners. Such tests are free from large angle-induced measurement errors, as the Doppler shift is created electronically. The phantom has been used to demonstrate that waveform index calculation package checking is quite feasable and can obtain highly reproduceable results as demonstrated using the PI package on a Doptek CW scanner. Although the realistic waveform was produced by a flow phantom, such phantoms have difficulty in maintaining waveform integrity (average power spectral density, envelope etc.) over time and are almost completely unportable. The ESI phantom, therefore, also provides an essential link enabling the same 'captured' flow phantom waveform to be used again and again on many different scanners with the typical ease of use (portability, speed of setup) of an electronic device.<
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