For many years, the ‘closed’ architecture of clinical scanners has made difficult, or impossible,... more For many years, the ‘closed’ architecture of clinical scanners has made difficult, or impossible, their use for the implementation and test of new imaging methods. To overcome this problem, open platforms, that is, highly flexible scanners with wide access to raw echo data, have been developed and are now increasingly used in ultrasound research laboratories. In this chapter, the characteristics of an ideal research platform are reviewed and compared to those of available open systems. After describing the architectures of two reference scanners with opposite features in terms of complexity, size, and cost, several examples of novel applications, which have been made feasible by the research platforms, are discussed.
The measurement of blood velocity in carotid is an important exam routinely performed in clinical... more The measurement of blood velocity in carotid is an important exam routinely performed in clinical practice. With the help of B-mode imaging, the operator places the Doppler sample volume in the carotid lumen, before switching the scanner to pulsed wave Doppler mode. Currently, only trained operators are able to carry out these operations by using expensive and complex systems. Unfortunately, points of care dislocated in rural areas or in developing countries often miss trained personnel. In this work, an automatic blind procedure for assessing the angle-corrected blood velocity in the carotid artery is proposed. The carotid position is detected through automatic, real-time segmentation of B-mode images, while a Doppler investigation from 2 different directions produces anglecorrected velocity estimation. The procedure was experimented on the ULA-OP research scanner, but it is shown suitable to be integrated in low-cost embedded electronics. Experiments on flow phantoms and volunteers show the efficacy of the method.
Current 3-D Vector Flow Imaging (VFI) techniques are typically limited by either low temporal res... more Current 3-D Vector Flow Imaging (VFI) techniques are typically limited by either low temporal resolution and/or high computational cost. In this work, we illustrate a 3-D high frame rate VFI method, which efficiently splits the 3-D (x, y, z) displacement estimation in two separate 2-D VFI estimations operated in the frequency domain. The echo-data received after the transmission of plane waves are beamformed and high-pass filtered before being VFI processed. The new method was experimentally tested by using the ULA-OP 256 research system connected to a 3 MHz, 256-element, 2-D spiral array. Phantom experiments were conducted in steady laminar flow conditions for different probe-to-flow angles. For the tested conditions, the mean relative bias was 11.5% with a standard deviation of 10.9%. The 2-step approach applied to the 2-D VFI technique makes the new 3-D VFI method accurate and computationally efficient.
Journal of the Acoustical Society of America, Sep 1, 2018
In a few years, ultrasound research platforms, also known as open scanners, have become a great t... more In a few years, ultrasound research platforms, also known as open scanners, have become a great tool for facilitating the experimental activities of ultrasound labs. Ideal platforms should be easily programmed to permit visualization of the region of interest, transmission of arbitrary sequences of arbitrary waveforms, acquisition of massive amounts of raw echo-data, and, possibly, real-time implementation of innovative processing methods. Such characteristics may be particularly relevant in lung ultrasound (LUS) applications, where quantitative methods designed around the lung properties are needed. In fact, since standard US- imaging is designed to handle impedance mismatches that are typically much lower than those found in lung tissue, LUS mostly relies on the qualitative interpretation of imaging artefacts. In particular, full control of all parameters influencing the transmit/receive modalities may allow the test of original transmit/receive strategies, while the access to raw-data may permit the off-line test of novel approaches. In this talk, the main characteristics of advanced open scanners will be reviewed, and sample applications not feasible with standard clinical scanners illustrated. Emphasis will then be given to the specific contributions that such platforms can provide to LUS. Phantom and in-vivo results obtained with the ULA-OP research platforms will be presented.
A dual beam vector Doppler method was proposed (DOI: 10.1016/j.ultrasmedbio.2009.11.004), in whic... more A dual beam vector Doppler method was proposed (DOI: 10.1016/j.ultrasmedbio.2009.11.004), in which one beam is continuously tracked perpendicular to the flow direction, and the second one is used to perform velocity measurements with known Doppler angle. Since two consecutive transmission (TX) and reception (RX) events (one for each beam) are needed, the effective Doppler pulse repetition frequency (PRF) is halved, thus facilitating the onset of aliasing when fast flow is investigated. In this work, the problem is solved by using a single TX sub-aperture and two RX sub-apertures of a linear array probe; the new approach was implemented and tested in real-time on the ULA-OP 256 open platform taking advantage of its parallel beamforming capabilities.
HAL (Le Centre pour la Communication Scientifique Directe), Sep 8, 2015
The electronic steering capability of 2D ultrasound probes makes them excellent candidates for re... more The electronic steering capability of 2D ultrasound probes makes them excellent candidates for real-time 3D imaging. However, considering that current ultrasound scanners rarely control more than 256 channels, it is necessary to optimize these probes to operate with a reduced number of active elements. By integrating acoustic simulations into a simulated annealing algorithm, we optimize the radiated profile of a 256 elements 2D ultrasound probe
Recent advancements of ultrasound vector Doppler techniques have boosted the investigation of 2D ... more Recent advancements of ultrasound vector Doppler techniques have boosted the investigation of 2D regions of interest (ROIs). Several methods were proposed, but their implementation on commercial systems is still limited by technical difficulties. First, the investigation of wide ROIs at high frame rate requires the transmission of plane waves and parallel beamforming in reception. Furthermore, the extraction of vector velocities along multiple lines is typically performed by computationally demanding multi-beam or speckle tracking techniques. In this work, we compare, in terms of accuracy and computational load, the performance offered by these two techniques when the vector velocities are estimated for increasing numbers of lines. Experimental results obtained by using the ULA-OP 256 research system confirmed similar performance in terms of accuracy, with overall bias and standard deviation lower than 20%. The assessment of beamforming and computational loads demonstrates that the speckle tracking technique based on frequency-domain displacement evaluation is convenient when vector velocities over 8 or more lines are detected.
For many years, the ‘closed’ architecture of clinical scanners has made difficult, or impossible,... more For many years, the ‘closed’ architecture of clinical scanners has made difficult, or impossible, their use for the implementation and test of new imaging methods. To overcome this problem, open platforms, that is, highly flexible scanners with wide access to raw echo data, have been developed and are now increasingly used in ultrasound research laboratories. In this chapter, the characteristics of an ideal research platform are reviewed and compared to those of available open systems. After describing the architectures of two reference scanners with opposite features in terms of complexity, size, and cost, several examples of novel applications, which have been made feasible by the research platforms, are discussed.
The measurement of blood velocity in carotid is an important exam routinely performed in clinical... more The measurement of blood velocity in carotid is an important exam routinely performed in clinical practice. With the help of B-mode imaging, the operator places the Doppler sample volume in the carotid lumen, before switching the scanner to pulsed wave Doppler mode. Currently, only trained operators are able to carry out these operations by using expensive and complex systems. Unfortunately, points of care dislocated in rural areas or in developing countries often miss trained personnel. In this work, an automatic blind procedure for assessing the angle-corrected blood velocity in the carotid artery is proposed. The carotid position is detected through automatic, real-time segmentation of B-mode images, while a Doppler investigation from 2 different directions produces anglecorrected velocity estimation. The procedure was experimented on the ULA-OP research scanner, but it is shown suitable to be integrated in low-cost embedded electronics. Experiments on flow phantoms and volunteers show the efficacy of the method.
Current 3-D Vector Flow Imaging (VFI) techniques are typically limited by either low temporal res... more Current 3-D Vector Flow Imaging (VFI) techniques are typically limited by either low temporal resolution and/or high computational cost. In this work, we illustrate a 3-D high frame rate VFI method, which efficiently splits the 3-D (x, y, z) displacement estimation in two separate 2-D VFI estimations operated in the frequency domain. The echo-data received after the transmission of plane waves are beamformed and high-pass filtered before being VFI processed. The new method was experimentally tested by using the ULA-OP 256 research system connected to a 3 MHz, 256-element, 2-D spiral array. Phantom experiments were conducted in steady laminar flow conditions for different probe-to-flow angles. For the tested conditions, the mean relative bias was 11.5% with a standard deviation of 10.9%. The 2-step approach applied to the 2-D VFI technique makes the new 3-D VFI method accurate and computationally efficient.
Journal of the Acoustical Society of America, Sep 1, 2018
In a few years, ultrasound research platforms, also known as open scanners, have become a great t... more In a few years, ultrasound research platforms, also known as open scanners, have become a great tool for facilitating the experimental activities of ultrasound labs. Ideal platforms should be easily programmed to permit visualization of the region of interest, transmission of arbitrary sequences of arbitrary waveforms, acquisition of massive amounts of raw echo-data, and, possibly, real-time implementation of innovative processing methods. Such characteristics may be particularly relevant in lung ultrasound (LUS) applications, where quantitative methods designed around the lung properties are needed. In fact, since standard US- imaging is designed to handle impedance mismatches that are typically much lower than those found in lung tissue, LUS mostly relies on the qualitative interpretation of imaging artefacts. In particular, full control of all parameters influencing the transmit/receive modalities may allow the test of original transmit/receive strategies, while the access to raw-data may permit the off-line test of novel approaches. In this talk, the main characteristics of advanced open scanners will be reviewed, and sample applications not feasible with standard clinical scanners illustrated. Emphasis will then be given to the specific contributions that such platforms can provide to LUS. Phantom and in-vivo results obtained with the ULA-OP research platforms will be presented.
A dual beam vector Doppler method was proposed (DOI: 10.1016/j.ultrasmedbio.2009.11.004), in whic... more A dual beam vector Doppler method was proposed (DOI: 10.1016/j.ultrasmedbio.2009.11.004), in which one beam is continuously tracked perpendicular to the flow direction, and the second one is used to perform velocity measurements with known Doppler angle. Since two consecutive transmission (TX) and reception (RX) events (one for each beam) are needed, the effective Doppler pulse repetition frequency (PRF) is halved, thus facilitating the onset of aliasing when fast flow is investigated. In this work, the problem is solved by using a single TX sub-aperture and two RX sub-apertures of a linear array probe; the new approach was implemented and tested in real-time on the ULA-OP 256 open platform taking advantage of its parallel beamforming capabilities.
HAL (Le Centre pour la Communication Scientifique Directe), Sep 8, 2015
The electronic steering capability of 2D ultrasound probes makes them excellent candidates for re... more The electronic steering capability of 2D ultrasound probes makes them excellent candidates for real-time 3D imaging. However, considering that current ultrasound scanners rarely control more than 256 channels, it is necessary to optimize these probes to operate with a reduced number of active elements. By integrating acoustic simulations into a simulated annealing algorithm, we optimize the radiated profile of a 256 elements 2D ultrasound probe
Recent advancements of ultrasound vector Doppler techniques have boosted the investigation of 2D ... more Recent advancements of ultrasound vector Doppler techniques have boosted the investigation of 2D regions of interest (ROIs). Several methods were proposed, but their implementation on commercial systems is still limited by technical difficulties. First, the investigation of wide ROIs at high frame rate requires the transmission of plane waves and parallel beamforming in reception. Furthermore, the extraction of vector velocities along multiple lines is typically performed by computationally demanding multi-beam or speckle tracking techniques. In this work, we compare, in terms of accuracy and computational load, the performance offered by these two techniques when the vector velocities are estimated for increasing numbers of lines. Experimental results obtained by using the ULA-OP 256 research system confirmed similar performance in terms of accuracy, with overall bias and standard deviation lower than 20%. The assessment of beamforming and computational loads demonstrates that the speckle tracking technique based on frequency-domain displacement evaluation is convenient when vector velocities over 8 or more lines are detected.
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Papers by Piero Tortoli