Abstract:
A method of ultrasound imaging exploits the fact that short ultrasound bursts with a frequency much higher than a bubble resonance frequency (fr) can excite the bubble to resonate at fr if the burst is repeated at a frequency equal or close to f r. Thus, ultrasound contrast agent having a natural resonance frequency of fr is deployed within a target object. The target object is irradiated with an ultrasound excitation signal having a signal frequency much higher than/- and comprising a series of bursts at a pulse repetition frequency sufficiently close to fr to effect resonant behaviour in the contrast agent. A response is obtaining from the contrast agent indicative of the resonant behaviour.
Abstract:
A medical diagnostic ultrasound imaging method fires a sequence of pulses into a body and then receives, beamforms (14), weights and sums (24) the resulting echo signals to suppress first order echoes. The sequence of pulses includes at least two pulses that differ in amplitude and phase. In one form, no two pulses of the sequence have the same amplitude and opposite phase. In another form, only linear echoes are suppressed. In a third form, second and third order echoes are preserved while linear echoes are suppressed.
Abstract:
A method for ultrasound data processing comprises transmitting an ultrasound excitation signal from each element of a transducer array and receiving a response signal from each element of a transducer array. Each response signal corresponds to a respective channel. Each response signal is sampled at one or more time points in the response signal to create a plurality of samples, each sample corresponding to a channel and a time point. The samples are divided into at least two groups. Response signals from the first group are beamformed and response signals from the second group are beamformed separately. The process is repeated over multiple data frames. The beamformed signals of each group are correlated over the multiple data frames and beamformed signals having a lower degree of correlation or negative correlation are selectively attenuated. An image output is generated from the correlation output. The at least two groups of channels may be selected to minimise the similarity of noise and/or the received acoustic field outside the main lobe.
Abstract:
Systems and methods for ultrasound imaging capable of achieving spatial resolutions that can resolve objects smaller than 300 μιη are described. Ultrasound is transmitted to and steered over a volume-of-interest that contains a microbubble contrast agent to individually excite microbubbles. Signal data is acquired in response to the transmitted ultrasound, and a plurality of images are reconstructed by beamforming the acquired signal data. The spatial resolution of the beamformed images can be further increased using techniques that determine the position of the microbubble within each image to a greater level of accuracy than the point spread function ("PSF") of the ultrasound system. The images can also be combined to produce a single high resolution image of the volume-of-interest using, for instance, a maximum pixel projection technique.
Abstract:
This invention employs multiple ultrasound pulse firings of either alternating phase and/or amplitude to detect nonlinear fundamental and subharmonic signals from microbubble contrast agents within living tissue, at high frequencies (- 15 MHz), e.g., with a linear array transducer. It can be shown that the contrast-to-tissue ratio (CTR) decreases with increasing ultrasound frequency because of nonlinear ultrasound propagation in tissue. However, using the subharmonic signal in addition to the nonlinear fundamental harmonic component, rather than the conventional second harmonic used at lower frequencies, provides appreciable signal strength to overcome the limitations of nonlinear tissue propagation. Additionally, the method provides for the ability to switch, at some desired frequency above 20 MHz, into a purely alternating phase inversion acquisition, in combination with bandpass filtering of the subharmonic frequency band, minimizing the losses in CTR as the frequency increases.
Abstract:
A method of calibrating ultrasound contrast agent signal data from a location in a medium containing a contrast agent, the method comprising the steps of: inputting first echo signal data from a first plurality of echo signals from time series ultrasound pulses, the ultrasound pulses differing in at least one of phase, amplitude and pulse duration; determining the contrast agent signal data from the first echo signal data from one or more of the echo signals; determining an attenuation correction factor from the first echo signal data from at least one of the echo signals; calibrating the contrast agent signal data with the attenuation correction factor to obtain calibrated contrast agent data for the location; outputting the calibrated contrast agent data.
Abstract:
An ultrasound technique exploits differences in statefulness of response in order to distinguish between the objects of interest. The method comprises transmitting a primary excitation signal and one or more secondary excitation signals; into a target medium receiving a corresponding plurality of responses from the target medium respectively resulting from the plurality of discrete excitation signals; and generating an output signal comprising the difference between the response to the primary excitation signal and either (i) the sum of the responses to the secondary excitation signals, or (ii) the sum of the response to a single secondary excitation signal and one or more time-shifted copies of the response to the single secondary excitation signal, the time shift being selected for appropriate alignment of the copy relative to the first response and the second response .