Marco Scabia

Hardware and software platform for real-time processing and visualization of echographic radiofrequency signals

In this paper the architecture of a hardware and software platform, for ultrasonic investigation is presented. The platform, used in conjunction with an analog front-end hardware for driving the ultrasonic transducers of any commercial echograph, having the radiofrequency echo signal access, make it possible to dispose of a powerful echographic system for experimenting any processing technique, also in a clinical environment in which real-time operation mode is an essential prerequisite. The platform transforms any echograph into a test-system for evaluating the diagnostic effectiveness of new investigation techniques. A particular user interface was designed in order to allow a real-time and simultaneous visualization of the results produced in the different stages of the chosen processing procedure. This is aimed at obtaining a better optimization of the processing algorithm. The most important platform aspect, which also constitutes the basic differentiation with respect to similar systems, is the direct processing of the radiofrequency echo signal, which is essential for a complete analysis of the particular ultrasound-media interaction phenomenon. The platform completely integrates the architecture of a personal computer (PC) giving rise to several benefits, such as the quick technological evolution in the PC field and an extreme degree of programmability for different applications. The PC also constitutes the user interface, as a flexible and intuitive visualization support, and performs some software signal processing, by custom algorithms and commercial libraries. The realized close synergy between hardware and software allows the acquisition and real-time processing of the echographic radiofrequency (RF) signal with fast data representation.

A Doppler system for dynamic vector velocity maps.

The aim of the vector Doppler technique is the quantitative reconstruction of a velocity field independently of the ultrasonic probe axis to flow angle. In particular, vector Doppler is interesting for studying vascular pathologies related to complex blood flows. A problem of vector Doppler is data representation in real-time that should be easy to interpret for the physician. In this work, we present a technique for dynamic display of vector velocity maps and some experimental results obtained in vitro with 2-D vector Doppler on flow phantoms reproducing complex flow conditions. An improvement in the map presentation was obtained by using velocity vector field interpolation. In this work, we considered the problem of spatial sampling for vector Doppler, establishing a relationship between sampling steps and scanning system characteristics. Finally, we developed a novel multimedia solution that uses both interpolated images and sound to discriminate between laminar and turbulent flows.

A real-time two-dimensional pulsed-wave Doppler system

An experimental system was developed to acquire and visualise in real-time two-dimensional (2-D) velocity maps. Data acquisition is performed by using a modified commercial echograph based on a 5-MHz, 128-element linear-array transducer with electronic focussing and beam steering. Additional electronics were integrated into the echograph to implement a 2-D Doppler system capable of measuring the velocity component on the scanning plane. Suitable axial and lateral scanning methods were studied to obtain Doppler measurements over a scanning area. A colour image of the estimated velocity field is presented in real time on a personal computer using different visualisation techniques. The system performance was tested experimentally both in vitro and in vivo on a human carotid artery.

FEMMINA real-time, radio-frequency echo-signal equipment for testing novel investigation methods

Fast echographic multiparameter multi-image novel apparatus (FEMMINA), is a hardware and software platform dedicated to ultrasonic signal and image processing. FEMMINA is able to operate with sequences of radio-frequency (RF) frames. Its architecture is designed to be modular, expandable, and aimed at implementing different ultrasonic investigation techniques. The first experimental characteristic of this system is in its capability to operate in real time with ultrasonic RF signals, starting from acquisition up to processing, storage, and visualization. The second characteristic is the user-system interactivity that allows one to modify the operation appropriately while observing results. Currently, FEMMINA works in both typical experimental situations to study novel investigation techniques and clinical field to validate the proposed methods in different human districts

A Real-Time 2-D Vector Doppler System for Clinical Experimentation

A real-time hardware software 2-D vector Doppler system has been realized by means of the FEMMINA platform. The system operates by performing two independent 1-D Doppler estimations on the scan plane of a linear array probe along different directions; the probe is connected to a commercial scanner. The reconstructed velocity is presented in real-time as superposition on the conventional B-mode images. Two different scanning techniques have been implemented, in order to carry out the 2-D Doppler investigation in the area of interest. These techniques allow to use the system both in vivo and in vivo. An extensive set of simulations has been performed in order to establish a gold standard regarding vector Doppler 2-D techniques, and to be able to assess the performance of the 2-D Doppler system by comparing simulated and experimental results. The whole real-time 2-D vector Doppler system is fully certified as hospital equipment, and thus it can be employed to carry out an experimental characterization of the 2-D Doppler technique in the clinical environment.

A 3-D PW ultrasonic Doppler flowmeter: theory and experimental characterization

A complete 3-D ultrasonic pulsed Doppler system has been developed to measure quantitatively the velocity vector field of a fluid flow independently of the probe position. The probe consists of four 2.5 MHz piezocomposite ultrasonic transducers (one central transmitter and three receivers separated by 120/spl deg/) to measure the velocity projections along three different directions. The Doppler shift of the three channels is calculated by analog phase and quadrature demodulation, then digitally processed to extract the mean velocity from the complex spectrum. The accuracy of the 3-D Doppler technique has been tested on a moving string phantom providing an error of about 4% for both amplitude and direction with an acquisition window of 100 ms.

A new combined open research platform for ultrasound radio frequency signal processing

Two interconnected electronic platforms were designed to realize an experimental, modular and expandable system allowing the researchers to develop and to test different ultrasonic investigation techniques. The first experimental characteristic of this system lays in its capability to operate in real time with ultrasonic radio frequency (RF) signals, starting from the ultrasonic illumination function, down to acquisition, processing, storage and visualization. The second characteristic is the system interactivity with allow to modify the operation appropriately while observing results at critical steps. The two combined platforms can be considered in two different manners; an experimental open laboratory system, but also a clinical instrument when a specific configuration is chosen for a particular application. The expandability and the flexibility of this combined platform make its employment possible in non destructive testing where linear and phased array probes are being gradually introduced as well.

RADIOFREQUENCY REAL TIME PROCESSING: ULTRASONIC SPECTRAL IMAGES AND VECTOR DOPPLER INVESTIGATION

Novel radio frequency processing techniques for biological tissue characterization with ultrasound are presented in order to improve the diagnostic power of ultrasonic echographic systems. Spectral images of biological “in-vitro” and “in-vivo” tissue, obtained through the Discrete Wavelet Packet Transform (DWPT) are presented, as well as velocity vector maps of blood flow obtained with 2-D Doppler investigation. The implementation of the Discrete Wavelet Packet Transform through a digital filter produces, for each acquired frame, real time spectral maps, in different frequency bands. Multi-parametric images are composed by merging these maps using a dedicated “balance image fusion” algorithm. New blood images, obtained without using the Doppler effect, for “in-vivo” and “in-vitro” experiments are presented based on the exploitation of non-linear ultrasound-medium interaction effects [1,2,3,4]. The proposed spectral processing procedure seems to be suitable to perform tissue characterization. Pathological portions inside tissue could be detected thanks to their different echo frequency content which in turns is determined by linear and non-linear ultrasonicmedium interaction. The target of future clinical applications is to investigate the potential of the procedure as a “virtual biopsy”. Vector Doppler multi parametric images are obtained with compound measurements of Doppler shifts along different directions, and superimposing the resulting 2-D velocity vector maps to the conventional morphological B-mode representation [5,6,7] The results, here presented, were produced by employing a hardware and software platform dedicated to ultrasonic signal and image processing [8,9,10]. The radiofrequency signal for multi parametric calculation and presentation with a multiprocessing digital architecture was used. This platform provides a multi analysis and

Ultrasonic Images of Tissue Local Power Spectrum by Means of Wavelet Packets for Prostate Cancer Detection

The aim of this work is to present a novel apparatus for experimental activity in research where a high frequency signal must be acquired and processed in real-time, and represented through a multi-image visualization tool. The proposed apparatus is a hardware and software platform dedicated to signal and/or image processing and fast data visualization. Currently the system is employed for studying new algorithms for biological tissue ultrasound investigation 1,2. Real-time operation mode designates clinical environment as its elective application because fast data processing is a necessary prerequisite in order to evaluate the on-line diagnostic performance of different investigation methods. Furthermore, for research purposes, the possibility to have simultaneous views of different ultrasonic parameters is essential for an efficient analysis, verification and modelling of the specific ultrasound-media interaction phenomenon .

Real Time Processing of the Radiofrequency Echo Signal for On-Line Spectral Maps

In this work we presented a hardware-software platform, which was designed to be expandable, modular, and adaptable to any other system which needs to produce significant and easily readable real time images. Such platform, being completely programmable, can also be reconfigured in dependence of the object being investigated.