The Impact of Analog Front-end Filters on Ultrasound Harmonic Imaging

Ultrasound (US) harmonic imaging has shown advantages in better spatial resolution and contrast compared to classic fundamental imaging, but it suffers from more attenuation due to the increased frequency. To achieve more penetration, high dynamic range (DR) front-end electronics is required to receive the weak harmonic components. Typical US front-ends use a variable gain amplifier (VGA) to compensate part of the required DR, in order to avoid using a highly sensitive analog-to-digital converter (ADC). However, in harmonic imaging, the received signal amplitude is dominated by the fundamental component, thus the VGA is less efficient for these small harmonics. An analog front-end filter can be used before the VGA to mitigate this issue but this has an impact on spatial resolution by changing the dominant frequency component and spatial pulse length of the received signal. In this work, a combined acoustic-and-electronic model is made to understand the impact of the use of an analog front-end filter in US harmonic imaging applications in terms of imaging resolution, contrast, and hardware requirements.