Real-Time High-Frame-Rate Cardiac B-Mode and Tissue Doppler Imaging Based on Multiline Transmission and Multiline Acquisition.

Cardiovascular diseases, the leading cause of death in the world, are often associated with the dysfunction of the left ventricle. Even if, in clinical practice, the myocardial function is often assessed through visual wall motion scoring on B-mode images, quantitative techniques have been introduced, e.g., ultrasound tissue Doppler imaging (TDI). However, this technique suffers from the limited frame rate of currently available imaging techniques that needs to be balanced with the field of view. High-frame-rate (HFR) cardiac imaging has been recently tested off-line by simultaneously transmitting multiple focused beams into different directions and acquiring raw channel data into a PC. Several image lines were then reconstructed from the echoes of each transmission (TX) event. The same approach has been used to increase the TDI frame rate without restricting the field of view. This paper demonstrates the real-time feasibility of multiline TX and acquisition methods for both HFR cardiac B-mode and TDI. These approaches have been implemented on the ULA-OP 256 research scanner, by taking care that the related resources were optimally exploited for these new applications. The obtainable performance in terms of image quality and frame rate has also been investigated. Experiments performed with a 128-element phased array probe show, for the first time, that real-time B-mode imaging is feasible at up to 1150 Hz without significant reduction in image quality or field of view. The implementation of a real-time TDI algorithm allowed obtaining TDI images with a frame rate of 288 Hz for a 90°-wide field of view. Finally, in vivo examples demonstrate the feasibility and the suitability of the method in clinical studies.

Real-Time Blood Velocity Vector Measurement Over a 2-D Region.

Quantitative blood velocity measurements, as currently implemented in commercial ultrasound scanners, are based on pulsed-wave (PW) spectral Doppler and are limited to detect the axial component of the velocity in a single sample volume. On the other hand, vector Doppler methods produce angle-independent estimates by, e.g., combining the frequency shifts measured from different directions. Moreover, thanks to the transmission of plane waves, the investigation of a 2-D region is possible with high temporal resolution, but, unfortunately, the clinical use of these methods is hampered by the massive calculation power required for their real-time execution. In this paper, we present a novel approach based on the transmission of plane waves and the simultaneous reception of echoes from 16 distinct subapertures of a linear array probe, which produces eight lines distributed over a 2-D region. The method was implemented on the ULAO-OP 256 research scanner and tested both in phantom and in vivo. A continuous real-time refresh rate of 36 Hz was achieved in duplex combination with a standard B-mode at pulse repetition frequency of 8 kHz. Accuracies of -11% on velocity and of 2°on angle measurements have been obtained in phantom experiments. Accompanying movies show how the method improves the quantitative measurements of blood velocities and details the flow configurations in the carotid artery of a volunteer.

Architecture of an Ultrasound System for Continuous Real-Time High Frame Rate Imaging.

High frame rate (HFR) imaging methods based on the transmission of defocused or plane waves rather than focused beams are increasingly popular. However, the production of HFR images poses severe requirements both in the transmission and the reception sections of ultrasound scanners. In particular, major technical difficulties arise if the images must be continuously produced in real-time, i.e., without any acquisition interruption nor loss of data. This paper presents the implementation of the real-time HFR-compounded imaging application in the ULA-OP 256 research platform. The beamformer sustains an average output sample rate of 470 MSPS. This allows continuously producing coherently compounded images, each of 64 lines by 1280 depths (here corresponding to 15.7 mm width and 45 mm depth, respectively), at frame rates up to 5.3 kHz. Imaging tests addressed to evaluate the achievable speed and quality performance were conducted on phantom. Results obtained by real-time compounding frames obtained with different numbers of steering angles between +7.5° and -7.5° are presented.

ULA-OP 256: A 256-Channel Open Scanner for Development and Real-Time Implementation of New Ultrasound Methods.

Open scanners offer an increasing support to the ultrasound researchers who are involved in the experimental test of novel methods. Each system presents specific performance in terms of number of channels, flexibility, processing power, data storage capability, and overall dimensions. This paper reports the design criteria and hardware/software implementation details of a new 256-channel ultrasound advanced open platform. This system is organized in a modular architecture, including multiple front-end boards, interconnected by a high-speed (80 Gb/s) ring, capable of finely controlling all transmit (TX) and receive (RX) signals. High flexibility and processing power (equivalent to 2500 GFLOP) are guaranteed by the possibility of individually programming multiple digital signal processors and field programmable gate arrays. Eighty GB of on-board memory are available for the storage of prebeamforming, postbeamforming, and baseband data. The use of latest generation devices allowed to integrate all needed electronics in a small size ( 34 cm ×30 cm ×26 cm). The system implements a multiline beamformer that allows obtaining images of 96 lines by 2048 depths at a frame rate of 720 Hz (expandable to 3000 Hz). The multiline beamforming capability is also exploited to implement a real-time vector Doppler scheme in which a single TX and two independent RX apertures are simultaneously used to maintain the analysis over a full pulse repetition frequency range.

Real-time vector velocity assessment through multigate Doppler and plane waves.

Several ultrasound (US) methods have been recently proposed to produce 2-D velocity vector fields with high temporal and spatial resolution. However, the real-time implementation in US scanners is heavily hampered by the high calculation power required. In this work, we report a real-time vector Doppler imaging method which has been integrated in an open research system. The proposed approach exploits the plane waves transmitted from two sub-arrays of a linear probe to estimate the velocity vectors in 512 sample volumes aligned along the probe axis. The method has been tested for accuracy and reproducibility through simulations and in vitro experiments. Simulations over a 0° to 90° angle range of a 0.5 m/s peak parabolic flow have yielded 0.75° bias and 1.1° standard deviation for direction measurement, and 0.6 cm/s bias with 3.1% coefficient of variation for velocity assessment. In vitro tests have supported the simulation results. Preliminary measurements on the carotid artery of a volunteer have highlighted the real-time system capability of imaging complex flow configurations in an intuitive, easy, and quick way, as shown in a sample supplementary movie. These features have allowed reproducible peak velocity measurements to be obtained, as needed for quantitative investigations on patients.

Prevalence, characterization and antimicrobial susceptibility of Salmonella enterica and Yersinia enterocolitica in pigs at slaughter in Italy.

In 2005-2008, 1152 samples (451 faecal samples, 451 carcass swabs and 250 tonsils) were collected from 451 finishing pigs slaughtered in three abattoirs of northern Italy. In two abattoirs, 34 scalding water samples were collected. The aim of this study was to investigate the faecal and palatine tonsil carriage rate of Salmonella enterica and Yersinia enterocolitica in pigs at slaughter and the degree of carcass contamination by these bacteria. Typing of the isolates, virulence characterization and antimicrobial testing were also performed. S. enterica was isolated from 21.5% of the faecal samples, 10.9% of the carcasses and 10.4% of the tonsils, but not from scalding water. Nineteen different serovars were identified among 172 S. enterica isolates. The prevalent serovars were Derby (41.3%), Rissen (12.2%), Typhimurium (11%), 4,[5],12:i:- (8.7%) and Give (4.1%). S. enterica ser. Typhimurium and S. enterica ser. 4,[5],12:i:- isolates were phage-typed and PT DT120 was the most common (23.5%). Y. enterocolitica was detected in 17.1% of the faecal samples, 2.4% of the carcasses, 10.8% of the tonsils and 11.8% of the scalding water samples. A total of 119 isolates were found, four of them in water. Of the 115 Y. enterocolitica isolates of pig origin, 24 (20.9%) were 4/O:3 and 4 (3.5%) were 2/O:9. Y. enterocolitica 4/O:3 represented 85.7% of the pathogenic isolates found in all types of samples and 100% of those found in tonsils. In 4/O:3 isolates the most common virulence-associated genes were ystA (100%), inv (95.8%), ail (87.5%) and yadA (54.2%). In 2/O:9 isolates the prevalent genes were ail (100%), inv (100%) and ystA (100%), followed by ystB (25.0%). The majority (75.7%) of Y. enterocolitica isolates was biotype 1A, belonging to 13 serotypes (O:3; O:5; O:4,32-4,33; O:6,30-6,31; O:7,8-8; O:7,8-8-8,19; O:7,13; O:8; O:9; O:13; O:16-16,29; O:41,42-41,43; O:52). The most common virulence genes in 1A isolates were inv (95.4%) and ystB (72.4%). The antimicrobial resistance test showed that all Salmonella isolates were susceptible to cefotaxime, ciprofloxacin, cefalothin, gentamicin and enrofloxacin. Resistances to tetracycline (56%), sulphonamide compounds (42%) and streptomycin (34%) were the most common. All Y. enterocolitica isolates were susceptible to ciprofloxacin, ceftazidime, cefotaxime, chloramphenicol, enrofloxacin, gentamicin, kanamicin and neomycin. Most isolates were resistant to cefalothin (92%) and ampicillin (89%). Apparently, carcass contamination by S. enterica and Y. enterocolitica was more likely attributable to cross-contamination than to self-contamination, suggesting that good hygienic measures and slaughtering procedures can control transmission of these pathogens to pork meat.

A reconfigurable and programmable FPGA-based system for nonstandard ultrasound methods.

The availability of programmable and reconfigurable ultrasound (US) research platforms may have a considerable impact on the advancement of ultrasound systems technology; indeed, they allow novel transmission strategies or challenging processing methods to be tested and experimentally refined. In this paper, the ULtrasound Advanced Open Platform (ULA-OP), recently developed in our University laboratory, is shown to be a flexible tool that can be easily adapted to a wide range of applications. Five nonstandard working modalities are illustrated. Vector Doppler and quasi-static elastography applications emphasize the real-time potential and versatility of the system. Flow-mediated dilation, pulse compression, and high-frame-rate imaging highlight the flexibility of data access at different points in the reception chain. For each modality, the role played by the onboard programmable devices is discussed. Experimental results are reported, indicating the relative performance of the system for each application.

ULA-OP: an advanced open platform for ultrasound research.

The experimental test of novel ultrasound (US) investigation methods can be made difficult by the lack of flexibility of commercial US machines. In the best options, these only provide beamformed radiofrequency or demodulated echo-signals for acquisition by an external PC. More flexibility is achieved in high-level research platforms, but these are typically characterized by high cost and large size. This paper presents a powerful but portable US system, specifically developed for research purposes. The system design has been based on high-level commercial integrated circuits to obtain the maximum flexibility and wide data access with minimum of electronics. Preliminary applications involving nonstandard imaging transmit/receive strategies and simultaneous B-mode and multigate spectral Doppler mode are discussed.

A critique to the European regulatory system.

The establishment of the European Medicines Evaluation Agency (EMEA) has resulted in 15 states of the European Union (EU) sharing a common system for the evaluation of new medicinal products, with important implications for both industry and patients including (1) the time and effort saved by member states in the evaluation of new drug applications; (2) more consistent and quicker availability of medicines in EU countries; and (3) the establishment of a homogeneous regulatory policy throughout the EU. However, there are some inconsistencies between the EMEA objective "to promote the protection of human health" (Council Regulation, 1993) and the current system. This article reviews the organization and procedures of the EMEA and makes some proposals for substantial modifications to the present system.

European regulatory policies on medicines and public health needs.

The establishment of the EMEA has been a revolutionary step in the European pharmaceutical system. The 15 Member States of the European Union now share a common system for the evaluation of new medicinal products entering the European market. The decisions taken apply to the whole EU, with important implications for both industry and patients who may benefit from new therapies. The main immediate consequences of this system are: i) the time and effort saved by Member States in the evaluation of new drug applications; ii) more consistent and quicker availability of medicines in EU countries; iii) the establishment of a homogeneous regulatory policy throughout the EU. Public health has been presented as the fundamental concern of the EMEA, the mission statement of which is 'to promote the protection of human health ... and of consumers of medicinal products'. However, we note that there are some inconsistencies with this objective and the current system, such as those regarding drug trial requirements and the institutional location and financing of the EMEA. In this paper, some aspects of the new system are reviewed and consideration given as to how they relate to public health needs. Proposals are made for debate alternatives and improvements to the present system that would better respond to patients' health needs.