A team of researchers at Gwangju Institute of Science and Technology has developed a new ultrasound imaging method using random wave interference. The proposed method can image nylon wires as small as 0.08-mm in diameter.
Diagnostic ultrasound systems are used in hospitals to produce images of the internal organs. Ultrasound is a pulse-echo imaging modality. The initial ultrasound wave is transmitted into the human body. The ultrasound wave partially reflects from the tissue of the human body. Reflected back ultrasound wave is sampled and saved as digital signals. The final ultrasound image is generated by processing the digital signals.
Compared to other diagnostic methods such as MRI, CT the Ultrasound is a most affordable imaging tool, however it has a lowest spatial resolution. Our goal is to enhance spatial resolution of ultrasound systems.
From the inception of ultrasound imaging the researches have extensively used a beamforming method. The beamforming is a term referred to focusing the ultrasound waves into a narrow beam. By scanning the area of interest with the focused beam, researchers can obtain the image of the internal organs such as liver, heart, and kidney. In our research, we developed a new imaging method called random interference imaging which does not require beamforming as well as scanning. Surprisingly, replacing traditional focusing and scanning with unfocused random interference we were able to achieve a higher spatial resolution.
We propose using unfocused transmission of excitation signals coded with pseudorandom sequences that yields an incident wavefront of random interference (RI). In our method, we represent the image as group of scatterers that can be identified by its spatial impulse responses. The received echo signals are the result of multiple reflections of the incident ultrasound wavefront from the scatterers. High-resolution ultrasound images are reconstructed using the a priori measurements of spatial impulse responses of individual point scatterers and sparse estimation.
The new findings show that ultrasound images can be successfully reconstructed by using an ultrasound wavefront of random interference. In the simulation study, the proposed method achieved a resolution of 0.25 mm, representing a four-fold improvement over conventional beamforming-based methods. In the real phantom experiment, we demonstrated that the proposed method can successfully reconstruct ultrasound images of nylon wires as small as 0.08-mm in diameter using a tissue-mimicking phantom.