Iterative trace reconstruction of aliased radio-frequency data obtained using harmonic imaging: A feasibility study

It is critical to use a proper spatial sampling, otherwise images suffer from grating lobes. However, the cost of a medical ultrasound scanner is strongly related to the channel count of the receive electronics. This has led to channel reduction using multiplexing or in-probe pre-beamforming methods at the cost of image quality or frame rate. An alternative is to reduce the receive channel count and reconstruct the non-aliased data from spatially aliased data. Last year we reported on a wavenumber frequency domain mapping based iterative trace reconstruction method developed for fundamental imaging. However, harmonic imaging is often used in medical imaging to further improve the image quality. As the reconstruction method assumes linearity, it is not a-priori clear whether the reconstruction will work satisfactory in combination with harmonic imaging. Here, the feasibility of using the method for harmonic imaging is investigated using in-vivo linear array data. The reconstruction algorithm operates by iteratively focusing and defocusing of the data using an imaging algorithm and uses intermittent thresholding to suppress the aliasing artifacts in the imaging domain. Properly sampled plane wave transmission datasets were recorded of the right common carotid artery of a healthy volunteer using a linear array transducer attached to a research system. The reconstruction technique significantly improved the image quality of all aliased datasets for both the fundamental and second harmonic imaging modalities. In fact, the reconstruction quality was slightly better for the second harmonic imaging case.