Larry Y. L. Mo

B-mode blood flow (B-flow) imaging

B-flow is a new technique that extends the resolution, frame rate, and dynamic range of B-mode to simultaneously image blood flow and tissue. B-flow relies on coded excitation to boost weak signals from blood scatterers and on tissue equalization to simultaneously display flowing blood and tissue without threshold decision and overlay. Various classes of codes such as Barker and Golay may be used. Clinical B-flow cineloops demonstrate 3/spl times/ resolution and frame rate improvement over color flow, which, together with over 60 dB of display dynamic range, are able to image hemodynamics and vessel walls with unprecedented clarity.

Adaptive receive aperture for ultrasound image reconstruction

A method for adaptively determining reconstruction signals in an ultrasound system comprises determining a size of a receive aperture, comparing the size of receive aperture at each imaging point with a predetermined number of reconstruction channels, if the size of the receive aperture is not greater than the number of reconstruction channels, processing received echo signals for the receive aperture to produce an ultrasonic image, and if the size of the receive aperture is greater than the number of reconstruction channels, preprocessing the received echo signals to produce reconstruction signals, the number of reconstruction signals being equal to the number of reconstruction channels. The reconstruction signals are further processed to produce an ultrasonic image. In one embodiment, the receive aperture is a function of location of an imaging point in a medium under investigation.

Ultrasound based quantitative motion measurement using speckle size estimation

An ultrasound system determines the relative movement in a first direction (F1) of first matter, such as blood flow, and second matter, such as an artery wall, in a subject under study (S). A beam (B1) of ultrasound waves defining a plurality of beam positions (BP1 and BP2) and beam axes (A1and A2) are moved in scan directions having components parallel to direction F1. First and second blocks of data representing the first and second matter, respectively, are generated. A processor (20) performs an estimation of speckle size on first data to obtain a first result, and performs analysis of the second block of data to obtain a second result. The two results are analyzed to obtain a measure of the relative movement of the first and second matter.

Ultrasound enlarged image display techniques

In an ultrasound scanner (90), signals responsive to received ultrasound waves are processed by a B-mode processor (222) and a computer (232). The data processed by the B-mode processor (222) is used to generate a display of a reference image in an area (120) of a display (100), and the data processed by the computer (232) is used to generate a region of interest (140) of the reference image and an enlarged image corresponding to the region of interest in another area (150) of the display (100), thereby improving the spatial resolution and frame rate of the displayed images.

Real-time ultrasound spatial compounding using multiple angles of view

A method and an apparatus for spatially compounding ultrasound frames by using multiple angle views. Successive image frames of pixel data are processed using a Sum of Absolute Difference registration algorithm. The multiple angle views are achieved by operator manipulation of a probe (2).

Method and apparatus for automatic muting of Doppler noise induced by ultrasound probe motion

A method and an apparatus for monitoring the wall signal input to the wall filter of a spectral Doppler processor to check for probe-motion-induced clutter. This clutter is typically of higher frequency and amplitude than that due to normal vessel wall motion. Some additional threshold logic is used to check for energy within a frequency band greater than the normal wall signal frequencies. If significant energy above some “rattle” threshold is detected for a predefined time interval, the Doppler audio is automatically muted. This can be effected at one or more points within the normal Doppler audio signal path in a conventional scanner. If the rattling clutter is no longer detected, the Doppler audio is re-activated or ramped up smoothly.

Zone-based color flow imaging

A zone-based technique for real-time color flow imaging is described. The technique utilizes a broad transmit beam which is equivalent to 20-50 focused transmit beams, such that the full field of view can be scanned using only 3-5 firings, times the flow sample count (FSC) required for color flow estimation. On receive, the channel domain RF data is pre-processed and accumulated in memory, and then transferred to a software-based image formation system, which performs dynamic receive focusing, clutter filtering, mean velocity estimation and scan conversion. Various methods of compensating for the lack of transmit focusing gain are discussed, including a larger FSC, over-sampling pulsed repetition frequencies, and coded excitation using FM chirp, Barker and Golay codes. Both 7.5 MHz linear array and 3 MHz curved array images obtained using a research platform show very good agreement with the predicted signal-to-noise-ratio (SNR) gain for a 5-chip Barker coded signal.

Ultrasound clutter filtering with iterative high pass filter selection

A system and method for ultrasound clutter filtering is provided. A processor is configured to iteratively select an optimal high pass filter for the progressive, ordered filtering of clutter from ultrasound color flow imaging data. The high pass filter input for each iterative selection and ordered set of high pass filters is the same original ultrasound color flow imaging data. The high pass filters have different cutoff frequencies whereby each high pass filter can be implemented using different structures. The system and method allow for filtering of clutter from ultrasound color flow imaging data until the clutter is substantially removed.

Zone-based B-mode imaging

A zone-based technique for real-time B-mode imaging is described. The technique utilizes a broad transmit beam from which many receive beams are formed, such that a full field of view image can be formed using only 5-15 firings. On receive, the RF data is pre-processed and accumulated in a channel domain baseband I/Q memory, and then transferred to a DSP-based imaging system, which performs dynamic receive focusing, detection, log compression, spatial filtering, and scan conversion. This technique and architecture extracts more information from each transmit firing, transforming the image formation rate problem from one of acoustic propagation time limitations, to processing speed limitations and thus, leverages Moores Law. The basic technique and architecture will be discussed, as well as providing several example images from different applications.

Quantitative analysis of subharmonic imaging using microbubbles in contrast imaging

Second-harmonic imaging (SecHI) has been widely used to improve the contrast of microbubbles with respect to tissue since microbubbles have a large second-harmonic response. Unlike tissue, microbubbles can also have a response at subharmonic frequency. In order to take advantage of subharmonics in contrast imaging, the image quality of subharmonic imaging (SubHI) and SecHI are analyzed through quantitative comparisons. Nonlinear tissue and bubble responses are simulated for numerical analysis. SubHI and SecHI modes are implemented on a Logiq 9 scanner (GE Healthcare, Milwaukee, WI, USA). Images of a flow phantom (ATS laboratories, CT, USA) with Sonazoid (GE Healthcare, Oslo, Norway) microbubbles are presented. The contrast-to-tissue ratio (CTR) and signal-to-noise ratio (SNR) are calculated with variations of the bubble concentration and the depth of the vessel tube. The experimental results agree well with the simulations. The CTR at the subharmonic frequency can be higher than the value in second-harmonics. For deep-lying bubbles, the CTR for SubHI is 15 dB higher than for SecHI. Although the SNR at the subharmonic frequency can be lower than that at the second-harmonic frequency, it is suggested that SubHI with high blood-to-tissue contrast may be useful when the sensitivity is a major concern.