Welcome to the second issue of PLANE WAVE, Verasonics’ Newsletter through which we share information about new products and technologies, emerging applications, conferences, training opportunities, and collaborations with researchers in ultrasound and ultrasonic technologies.  We hope you find these newsletters informative and interesting, and welcome your suggestions for future topics.

Volume Imaging with High Channel Counts
and High Element Counts

Background

As scientists and researchers explore new ways to use ultrasonics, there is an increasing need to employ more elements and more channels. This is particularly true in the field of diagnostic medical ultrasound, where physicians have utilized 3D imaging to better understand complex anatomical structures, and 4D ultrasound (3D in real-time) to depict moving structures such as the valves in the heart.

For imaging moving structures, or to acquire a volume of data at high-speed, the optimal transducer is an electronically-steered phased array that uses a two-dimensional grid of elements. This type of transducer is often called a matrix array and may utilize hundreds or even thousands of elements. Several transducer manufacturers are now making matrix arrays in 8×8, 16×16, 32×32 and even higher element configurations.

There are some clinical ultrasound systems that employ matrix arrays, however these typically utilize only 192 or 256 channels. The transducers are multiplexed, and use “micro-beamforming” techniques to reduce the programming complexity and data volume that these probes can acquire. Many scientists and researchers, however, would prefer to have a direct connection to every element for maximum flexibility, absolute control and complete data acquisition.

Verasonics’ Vantage 256 research ultrasound system, with UTA 1024-MUX adapter and 1024-element matrix array transducer

The UTA 1024 MUX adapter can be removed and replaced with another adapter in a few minutes, to provide maximum flexibility for the researcher.

The Vantage Solution

Vantage systems by Verasonics are capable of various configurations that support high-element-count matrix arrays, using one or multiple systems. For example, a single 256 channel Vantage system with a 4-to-1 multiplexer adapter has the ability to multiplex up to 1,024 elements. The same 1,024-element transducer can also be direct connected to four Vantage systems, or to two Vantage systems with two multiplexers. A researcher can start with one Vantage system and later acquire additional systems to implement a full 1024-channel system that can connect directly to every one of the 1024 elements in the array. Other custom combinations of systems and transducer element counts may be considered for special configurations to accommodate specific research and exploration needs.

One of the challenges in combining multiple systems for research or product development is the synchronization of transmit and receive clocks for each system. Verasonics has developed a Multi-System Synchronization Module that can synchronize up to 8 Vantage systems for a total of 2048 channels. Multi-System clocks are synchronized to within 2ns by simply connecting via HDMI cables to the Multi-System Synchronization Module.

The Multi-System Vantage configurations define one system as the master, with one or more slave systems. Scripts are run on each system, and these scripts are synchronized using the input/output triggers. RF data is transferred from the slave system to the master through a serial interface. Data is collected in the master system and then can be processed and displayed by the master system.

The unique Pixel-Oriented Processing software of the Vantage system makes it possible to create transmit and receive beamforming delays for virtually any transducer geometrical configuration and element positions, enabling the implementation of novel transducers and systems. The software is extremely flexible and allows for each element to have a separate geometric orientation from other elements in the same experiment or system. This flexibility is compatible with any shape, size or combination of transducers. For example, Vantage enables the user to implement 3D concave (bowl-shaped) transducers, ring arrays, 1D and 1.5D arrays, 2D matrix arrays, multiple simultaneous arrays and sparse arrays, as well as through-transmission ultrasound techniques. Experiments can be simulated using Vantage software before running the experiment on the Vantage hardware and transducer.

To see a video clip of a 3D volume acquired with this product configuration, click here.

Applications of High Element and Channel Count Imaging:

High-element-count transducers and high-channel-count beamforming have many applications, including the rapid acquisition of a data set for a volume of tissue or material. Whereas conventional ultrasound imaging only acquires information along a single line or plane, matrix arrays enable volume imaging to characterize changes in structural properties or physiological events. For example, the deformation of a structure under stress can be better understood if the visualization is not limited to a single plane. Likewise, quantitative analysis of perfusion within tissue (wash-in, wash-out processes) may require that the entire volume be evaluated.  Researchers doing functional imaging want to be able to characterize the blood flow changes throughout the area of interest, not only in a single plane.

Another application is in therapeutic ultrasound. Researchers in the field of HIFU not only want to direct the delivery of energy in multiple planes, but also want to know how the tissues adjacent to the treated tissue are responding to that energy. A matrix array, controlled by a high-channel-count system, can facilitate these objectives.

Finally, there is another potential for high-channel-count systems in the area of aberration correction. With conventional 2D imaging there is often image degradation due to echoes produced by out-of-plane structures. These structures are not visible, but the artifacts they produce can create confusing and misleading information. Current techniques for aberration correction can address artifacts that arise from in-plane structures, but not those from structures that lie out of the scan plane. A matrix array transducer, controlled by a high-channel-count system, provides opportunity for the researcher to detect and mitigate these artifacts.

See Verasonics at these upcoming conferences:

JSUM Ultrasonic Week
26-28 May – Utsunomiya, Japan

International Society of Therapeutic Ultrasound
31 May–2 June – Nanjing, China

Ultrasonic Imaging and Tissue Characterization
5-7 June – Arlington, VA, USA

Contact us for more information
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