Glen McLaughlin

Ultrasound imaging system

Echolocation data is generated using a multi-dimensional transform capable of using phase and magnitude information to distinguish echoes resulting from ultrasound beam components produced using different ultrasound transducers. Since the multi-dimensional transform does not depend on using receive or transmit beam lines, a multi-dimensional area can be imaged using a single ultrasound transmission. In some embodiments, this ability increases image frame rate and reduces the amount of ultrasound energy required to generate an image.

Ultrasound system with cableless coupling assembly

An ultrasound imaging device having a cableless coupling for coupling a two-dimensional array of ultrasound transducers to a signal generating and receiving unit such as a motherboard. The coupling includes an acoustically attenuating and electrically conductive structure, which can include posts that are electrically conductive or electrically insulative having a conductor embedded or mounted on the outer surface. There can also be a high density connector allowing coupling and de-coupling the two dimensional array to and from the motherboard.

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.

RSNA QIBA ultrasound shear wave speed Phase II phantom study in viscoelastic media

Using ultrasonic shear wave speed (SWS) estimates has become popular to noninvasively evaluate liver fibrosis, but significant inter-system variability in liver SWS measurements can preclude meaningful comparison of measurements performed with different systems. The RSNA Quantitative Imaging Biomarker Alliance (QIBA) ultrasound SWS committee has been developing elastic and viscoelastic (VE) phantoms to evaluate system dependencies of SWS estimates. The objective of this study is to compare SWS measurements between commercially-available systems using phantoms that have viscoelastic properties similar to those observed in normal and fibrotic liver. CIRS, Inc. fabricated three phantoms using a proprietary oil-water emulsion infused in a Zerdine® hydrogel that were matched in viscoelastic behavior to healthy and fibrotic human liver data. Phantoms were measured at academic, clinical, government and vendor sites using different systems with curvilinear arrays at multiple focal depths (3.0, 4.5 & 7.0 cm). The results of this study show that current-generation ultrasound SWS measurement systems are able to differentiate viscoelastic materials that span healthy to fibrotic liver. The deepest focal depth (7.0 cm) yielded the greatest inter-system variability for each phantom (maximum of 17.7%) as evaluated by IQR. Inter-system variability was consistent across all 3 phantoms and was not a function of stiffness. Median SWS estimates for the greatest outlier system for each phantom/focal depth combination ranged from 12.7-17.6%. Future efforts will include performing more robust statistical analyses of these data, comparing these phantom data trends with viscoelastic digital phantom data, providing vendors with study site data to refine their systems to have more consistent measurements, and integrating these data into the QIBA ultrasound shear wave speed measurement profile.

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.

Biphasic transdermal iontophoretic drug delivery platform

Transdermal iontophoresis is an active drug delivery method that has the potential to transform treatment of conditions such as acute pain that require a succession of on-demand metered-dose drug deliveries. However, current monophasic iontophoresis methods fail to meet these requirements due to their inability to halt the passive diffusion of active agents when therapy is not required. We have developed a biphasic iontophoretic system to overcome these limitations. The viability of this system was assessed in an in vitro porcine skin preparation using FeCl2 (127 Daltons), a charged molecule which can undergo both active and passive transdermal diffusion. The transport properties of the system were modeled using a Fourier Transform-derived optimum estimate transfer function. Using this model, experimental results showed good correlation to predicted values for both cumulative dose (R2=0.912, n=10), and density dose (R2=0.802, n=10). Results also showed the ability to effectively deliver the compound during active periods while minimizing delivery during inactive periods. While preliminary, our results suggest biphasic iontophoresis is a viable means of delivering on-demand drug therapy while minimizing unwanted off-demand delivery.

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.

Acoustic clutter supporession with weighted phase-difference coherence factor

Various forms of coherence factor have been proposed to improve spatial resolution and suppress acoustic clutters. Regardless of the forms of definition, coherence factors evaluate focusing quality at given field points based on the degrees of coherence of the aperture data. These methods work effectively for coherent sources such as pin targets, whose correlation length is infinite. For incoherent sources with finite correlation lengths, however, the coherence factors suffer from the decorrelation effect from the source. As a consequence, most of the coherence factors tend to introduce large speckle variance. In this paper, we propose the weighted phase-difference coherence factor (WPD-CF) and its computation-efficient form vector coherence factor (VCF), in an attempt to suppress acoustic clutters while preserving tissue speckles. By evaluating the degrees of coherence of the phase differences, WPD-CF precisely segments pin target main lobes, pin target side lobes, grating lobes, soft tissue speckles, and random acoustic clutters. A computation-efficient form of WPD-CF, named vector coherence factor (VCF), were derived based on the fact that the cosine of the angle between two vectors is proportional to their dot product. The advantages of WPD-CF and VCF were demonstrated by phantom and in vivo imaging results.

Synthetic transmit beam steering for spatial compounding applications using continuous transmit focusing

Traditional spatial compounding, in general, employs multiple distinct transmit/receive beam angles which insonify a common region, from which multiple images are formed. The individual images are detected, resampled onto a common grid, and combined in order to produce better image quality, whose attributes are better contrast resolution, reduced speckle, reduced shadowing artifacts, and better borders. However, the increase in image quality comes at a cost in increased acoustic acquisition time, with a corresponding drop in frame rate. Combination modes such as B+CD places heavy demands on acquisition time, and in order to maintain adequate frame rates, the number of B-mode spatial compounding views is reduced or eliminated when in CD-mode, reducing B-mode image quality. In order to provide spatial compounding while maintaining the same acoustic acquisition time, multiple steered transmit beams are synthesized from the same set of channel data acquired for the non-steered view, using a continuous transmit focusing technique.

Set It and Forget It: Innovations in Implantable Medical Technology

Implantable medical devices impose a tremendous set of constraints on their system-level components. The limitations of these components inevitably result in design compromises that become necessary in order to achieve minimum therapeutic requirements. Recent advances, from companies like Texas Instruments, in the semiconductor industry in power consumption, reliability, real-time processing, chip-level integration, and packaging have made possible a new wave of implants. Gene Frantz has influenced several of these advances. This article looks at the challenges faced by the systems engineer embarking on the designs of tomorrows implants, using todays technologies while preparing for the advances yet to come.