Performance testing of medical ultrasound equipment: fundamental vs. harmonic mode

Assessment of the performance of medical ultrasound equipment is generally based on the image quality in fundamental mode. Recent development of the so-called tissue harmonic imaging (THI) mode induces the need for assessment of differences in the quality of imaging in THI vs. fundamental imaging mode. Quality features to be tested are sensitivity (penetration depth), spatial resolution, contrast resolution, lesion signal-to-noise ratio, and tissue-to-clutter ratio (TCR). These features are explained and examples are shown. The main conclusion from a comparison of the results for the two imaging modes might be that when using THI improvement of TCR, in particular in the near field, is obtained at the expense of a loss in axial resolution. Furthermore, lesion detection is not significantly improved.