DOPPLER TWINKLING ARTIFACT OBSERVATIONS: AN OPEN-ACCESS DATABASE OF RAW ULTRASONIC SIGNALS

Backgraund: Doppler twinkling artifact is a rapid change of colors seen in CFI-mode in the presence of kidney stones, calculi, etc. Therefore some try to use the twinkling artifact as a useful diagnostic sign; however this phenomenon is underresearched, because the majority of assumptions concerning its causes are made on the basis of pure visual observations of the scanners screen living the important steps of signal transformation hidden behind the black box curtains of ultrasound machines. Methods: Raw radiofrequency ultrasound signals were recorded in the phantom studies. The recorded echoes were received from objects which create the Doppler twinkling artifact and also from artificial blood vessels and soft tissues imitators. The data were collected between June 2016 and March 2021. Sonomed-500 with the 7.5 L38 and 3.4 C60 probes served as the research machine for the signal capture. Data records: We present the database containing raw radiofrequency ultrasound signals from the beamformer output of the research ultrasound machine. The dataset consists of CFI and B-mode echoes recorded from twinkling objects. Therefore, this database can be useful for those who test, develop and study ultrasound signal processing algorithms. The database is freely available online. The database consists of echoes received from five phantoms with the total size of 10.5 GB. Raw radiofrequency signals were stored in the binary files; scanning parameters were stored in text files. The database is available at: https://mosmed.ai/datasets/ultrasound_doppler_twinkling_artifact. Code availability: Anyone can study the database with the specially written program called TwinklingDatasetDisplay available at: https://github.com/Center-of-Diagnostics-and-Telemedicine/TwinklingDatasetDisplay.git. Usage notes: The database can be used to test and develop signal-processing algorithms, such as wall filtration, velocity estimation, feature extraction, speckle reduction, etc. Anyone is free to share (copy, distribute, and transmit) and to remix (adapt and make derivative works) the dataset as long as appropriate credit is given.

Optimizations for FPGA-Based Ultrasound Multiple-Access Spread Spectrum Ranging

Indoor localization based on ultrasound signals has been carried out by several research groups. Most of the techniques rely on a single ultrasound pulse ranging, where the Time of Flight between the ultrasound emitters and a receiver is computed. Ultrasound orthogonal modulation techniques have also been investigated and allow to compute the range between the receiver and multiple simultaneous emitters with increased accuracy. However, no comparative investigation on the possibilities of each of the modulation techniques, comprising Direct Sequence Spread Spectrum, Frequency Hopping Spread Spectrum, and Chirp Spread Spectrum, could be found. Also, common optimized demodulation and correlation techniques for FPGA ready implementations are not widely available. Moreover, the hardware requirements for capturing modulated ultrasound signals could not be found for all the techniques. In this work, the different modulation techniques are optimized and implemented on an FPGA. A dedicated custom ultrasound MEMS-based receiver hardware for broadband ultrasound signal capturing is developed. Several modulation parameters are developed and applied for optimized signal processing. The FPGA resource consumptions are evaluated for the implemented methods. All methods are compared against the regular pulse ranging method, in both single-access and multiple-access ranging mode. Results show that, on average, up to 8 ultrasound-modulated emitters with an orthogonal sequence of length 63 can be demodulated on a Zynq7020 FPGA. In most cases, ranging up to 8 m is demonstrated in both single- and multiple-access mode, with accuracies generally remaining at a centimeter level. The requirements and capabilities for each of the modulation schemes are highlighted in the conclusions.