Ultrasonic B-Mode Imaging
Ultrasonic B-mode imaging is one of the most common and widely used techniques in the biomedical industry. My job duties at eSonic Image are mainly transmitting and receiving beamforming algorithm development and verification using experimental phantom data for various probes and modes.
TX Beamforming
Transmitting (TX) beamforming is the first step performed, which aims to form a focused beam at a given depth underneath the probe surface.
In order to form a wanted beam at a focal, a time delay calculation is performed, which aims to determine when to excite piezos on the probe.
The right video shows an example of a curved array (i.e., a convex probe) for forming focused beams. There are two figures, with the first one showing the calculated delayed time for each ultrasonic piezo and the second one highlighting the excited piezos in yellow, the focal in red point, and the focal trajectory of the formed beams in magenta.
Note: the beam focus is moving from left to right with the same depth periodically, so the trajectory is a circular arc.
TX Beam Pattern
The right video shows TX beam pattern of the formed focused beams of a curved array.
Note: both main lobe and side lobe can be seen from the video. For some probes and modes, even grating lobes can be observed, which would hurt the B-mode image quality. Therefore, additional processing and imaging steps are needed to suppress this effect.
RX Beamforming
Receiving (RX) beamforming aims to process raw waveform data from each piezo element and produce the beamformed image. There are a series of processing steps, which include transmitting/ receiving path calculation, receiving apodization, phase rotation, and delay-and-sum algorithm.
The right figure shows the geometry relation of a curved array, which includes the transmitting path in blue, receiving path in red, and an image pixel in black point on the beamformed line.
Please search other published materials for more details.
Beamformed Images
The gallery below presents beamformed images from different probes and modes, which include linear/ curved/ phased arrays with focused beams, linear arrays with trapezoid expansion, linear and curved arrays with steering angles (compound), and linear arrays with plane waves for ultrafast imaging.
