Verasonics Announces Application Scripts to Enhance Research
Application Scripts are a new offering from Verasonics that will benefit both new and experienced users looking to reduce start-up time when embarking on efforts in developing ultrasound research areas. These scripts, developed by the Verasonics Ultrasound Science team, are designed to allow new users to learn about, then integrate, ultrasound imaging or ultrasound therapy algorithms or techniques that may be quite complicated.
For experienced Verasonics customers, Application Scripts may demonstrate lesser-known features of the Vantage® and Vantage NXT platforms or provide examples of how to optimize system performance.
Each Application Script package includes the MATLAB®-based Verasonics sequence files plus any external functions or data required. Additionally, the package will contain documentation providing a summary of the MATLAB sequence and theory of operation, how to run the sequence on the Vantage or Vantage NXT platform, and any other experimental details needed to exercise the Application Script.
These scripts will be available free of charge to Vantage and Vantage NXT platform owners via the Verasonics Community Portal and will focus on the research areas noted below. Photoacoustics and TSI scripts will be added to the portal by end January, CEUS scripts by end February.
- Photoacoustics – Vantage and Vantage NXT enhanced example scripts for getting started in photoacoustic imaging
- Tissue Strain Imaging (TSI) – Vantage example script and functions for TSI in ablation monitoring
- Contrast Enhanced Ultrasound (CEUS) – Vantage NXT example scripts for CEUS imaging
Additional scripts will be added in the coming year; Verasonics also welcomes customer feedback on application script topics. Please send topic suggestions to [email protected].
Remember – all customers have 24/7, no cost access to the Verasonics Community Portal. This customer service and support portal includes introductory training videos, training webinars resource and accessory documentation, and now, application scripts! For questions related to portal access, please contact [email protected].
Verasonics Announces New 3 MHz Matrix Array Transducer
The M3dV 3 MHz Matrix Array Transducer features a new monolithic design over current versions of the 3 MHz Matrix Array transducer, as noted in Figure 4 below. Users will appreciate a uniformity of element position across the array, which enhances image reconstruction and offers improved image quality while reducing a calibration requirement.
Utilizing 1024 elements in a 32×32 grid, the M3dV is compatible with the Vantage NXT and Vantage 256 Research Ultrasound Systems. Verasonics systems will include example scripts for multiplexed acquisition sequences, as well as scripts for direct acquisition for one-to-one channel-to-element connections in Q1 2025 software releases for both platforms.
Figure 4: Comparison of existing transducer design to new 3MdV transducer design.
Enhanced Photoacoustic Imaging Capabilities with the Vantage NXT Research Ultrasound System – Case Examples
Photoacoustic (PA) imaging is a hybrid imaging technique that uses light, typically from a laser source, to generate ultrasound waves by converting optical energy absorption to heat the medium, resulting in abrupt thermal expansion that launches an ultrasound wave during the optical burst. This modality utilizes optical absorption contrast in combination with ultrasound resolution to image biological chromophores, such as hemoglobin, collagen, melanin or lipids; these chromophores have structured absorption spectra and specific optical wavelengths can be used to tune the effect to constituents of particular biological interest. For example, photoacoustics can image the hemoglobin content and oxygen saturation in blood, as well as detailed biochemical characterization through spectroscopy of tissue components. Non-absorbing structures may be visualized with the aid of exogenous contrast agents such as molecular dyes and by antibody-targeted absorbing particles or molecules to identify the location of specific receptors. Thus, the PA imaging technique has diverse applications, including molecular imaging for oncology, therapy monitoring, cardiac imaging for the detection of atherosclerotic plaques, and the detection of hematological diseases.
Despite its extensive applications, the modality faces a few limitations that hinder clinical translation. Due to the combined effects of superficial scattering and absorption, the optical fluence drops sharply with depth in biological tissues. As a result, photoacoustic signals that are generated from deep-seated chromophores are often more than an order of magnitude weaker than typical pulse-echo signals. Optimal signal-to-noise ratio of the received signals along with a large analog and digital dynamic range receiver is of key importance to accurately represent these weak target signals. Therefore, a high-performance acquisition system is essential.
In this context, the Verasonics Vantage NXT Research Ultrasound System can provide enhanced detection of PA signals over the prior Vantage System due to a number of hardware improvements, foremost among them higher ADC bit depth (16 vs. 14 bits) and increased sampling rate (125 vs. 62.5 MHz), delivering improved dynamic range and SNR (Signal-to-Noise Ratio) of received signals in the same band. The noise figure of the signal path, including the passive circuitry around the AFE (Analog Front End) is 2.7 dB at 50 Ω input impedance in the Vantage NXT System and slightly better than the 3 dB in the Vantage System (Application Note – Vantage/Vantage NXT analog signal path gain). Furthermore, the possibility to accumulate raw RF data in Vantage NXT hardware using the new half-precision (16-bit float) datatype also contributes to improved dynamic range, and thus the overall SNR, while minimizing the amount of data to be transferred to the host controller. Finally, the receive frequency operating range of the Vantage NXT high frequency system is much wider (0.25 MHz to 60 MHz) than that of the Vantage System (1MHz to 50 MHz for the high frequency configuration and 0.5MHz to 27MHz for the standard frequency configuration). This wide receive operating band allows for higher resolution imaging capability limited only by transducer design and sensitivity.
In addition to the detection of weak acoustic signals, a key requirement in PA imaging is having an acquisition system that is well synchronized with the laser source. As a wide variety of laser systems are used for PA imaging each with different synchronization characteristics, flexibility in trigger configuration is critical in the acoustic acquisition hardware. The Vantage NXT System was designed to have 4 programmable trigger connections that can be used as either trigger inputs or trigger outputs. The output trigger capability of the older Vantage System only included one connector delivering a 3.3V, 1 μs duration Active Low pulse with programmable delay. The output triggers from Vantage NXT can produce pulses with:
- 3.3-Volt or 5-Volt signal level
- Active Low or Active High pulse polarity
- Output pulse duration set to 1 μsec, 100 μsec, 1 msec, or 10 msec
- Programmable delay from 0 to 4.2 μsec (delay from the start of the associated event to the leading edge of the trigger out pulse)
This flexibility simplifies adapting the Vantage NXT acquisition sequence to suit the triggering needs of the different types of laser systems that the customer may use. The programmable output trigger eliminates the need for a function generator in most cases. Repeatability is greatly enhanced when Vantage NXT triggers the laser (usually its Q-Switch) instead of being triggered by the laser; this approach greatly reduces jitter for coherent summation using multiple laser firings.
A collaborative project has been undertaken with Prof. Gijs van Soest, Erasmus University Medical Center (Erasmus MC, Rotterdam, The Netherlands) to compare photoacoustic image quality between the Vantage NXT 256 High Frequency System and the Vantage 256 High Frequency System. All the images were acquired using a pulsed laser diode at wavelength 808 nm (Quantel Laser, France) pulsed at 1 kHz PRF, with 1.18 mJ pulse energy, delivered through a fiber bundle. Results obtained from printed phantoms (Courtesy of Dr Francis Kalloor Joseph, Erasmus MC, Rotterdam, The Netherlands) shows increased sensitivity and contrast in the data acquired with the Vantage NXT System, for all transducers consistently.
Figure 1: Comparison between PA images obtained with a Verasonics L11-4v probe using (a) Vantage and (b) Vantage NXT System. (c) A plot of the depth profiles along the dotted lines in figures (a) and (b). The white arrows marked in figure b point to vessels that are present in deeper locations which are hardly visible with Vantage but are visible with Vantage NXT. These figures were obtained by averaging 5 laser firings.
Figure 2: Comparison between PA images obtained with a Verasonics L11-5v probe using (a) Vantage and (b) Vantage NXT system. (c) A plot of the depth profiles along the dotted lines in figures (a) and (b). These figures were obtained by averaging 5 laser firings.
The images shown above in Figure 1 and Figure 2 demonstrate improved SNR and increased photoacoustic signal amplitude with Vantage NXT. The SNR in Figure 1 and Figure 2 was measured at 25 dB vs 19 dB for Vantage NXT vs Vantage respectively. Additionally, due to weak signals close to the noise floor in Vantage, gain settings often must balance PA signal detection versus near-field saturation. This is specifically noticeable in Figure 1a. The lower noise floor in Vantage NXT is therefore useful in detecting superficial targets and weak targets present at larger depths as pointed out by the arrows in Figure 1b.
Figure 3: Comparison between photoacoustic images obtained with a Vermon L22-14vx probe using a) Vantage and b) Vantage NXT System. c) shows a picture of the phantom used for imaging and the portion within the red circles indicate the region illuminated using a round fiber bundle. These figures were obtained by averaging 35 laser firings.
Figure 3 shows the photoacoustic images acquired with a phantom (Figure 3c) from Vantage NXT and Vantage using a high-frequency linear array for detection. Some of the targets with weaker absorption remain undetected in the Vantage, whereas they are clearly visible with better contrast in Vantage NXT.
Overall, the results of the collaboration demonstrate that the new Vantage NXT hardware features and specifications improve performance in PA imaging for researchers. Many existing PA researchers face challenges in synchronizing their laser systems with Vantage without the aid of external circuitry. Now, the programmability feature of the triggers in Vantage NXT offers great flexibility for customers to directly synchronize ultrasound acquisition with different laser models. Further, the improved ADC bit depth from 14 to 16 bit in addition to the higher ADC sampling rate of 125 MHz in Vantage NXT in comparison to 62.5 MHz in Vantage contributes to improved detection of weaker photoacoustic signals. Customers can also accumulate raw RF data using half (16-bit float) datatype in Vantage NXT hardware to further improve dynamic range and reduce the amount of data transferred to the host controller to a minimum.
These features of Vantage NXT will help existing customers improve PA research and allow new PA researchers to get up to speed more rapidly.
For questions on Verasonics solutions, contact [email protected].