Mayo Foundation for Medical Education and Research

Shigao Chen

James Fowler Greenleaf

Pengfei Song

Armando Manduca

Matthew W Urban

Joshua D Trzasko

Heng Zhao

Ping Gong

Yi Zheng

Carolina Amador Carrascal

Daniel C Mellema

Aiping Yao

Chengwu Huang

Mostafa Fatemi

Bo Qiang

Igor A Lavrov

Riazul Islam

Ivan Z Nenadic

Randall Kinnick

Alireza Nabavizadehrafsanjani

Shanshan Tang

Wei Tan

Matthew Lowerison

Systems and methods for removing the bias induced by noise from power Doppler images to achieve improvements of microvessel image contrast are provided. In one example, the noise-induced bias can be suppressed by utilizing the characteristics of uncorrelated noise in the ultrasound image from data acquired or compounded at different transmitting angles. In another example, the noise-induced bias can be suppressed due to the lack of correlation between adjacent ultrasound images. These example implementations may also be combined, as will be described below.

Systems and methods for removing noise-induced bias in ultrasound blood flow imaging

Functional ultrasound imaging ('fUS') is used to facilitate the placement of electrodes for spinal cord stimulation and to optimize and update stimulation parameters for spinal cord stimulation devices.

Functional ultrasound imaging for spinal cord stimulation electrode guidance and stimulation parameter optimization

Systems and methods for high spatial and temporal resolution ultrasound imaging of microvessels in a subject are described. Ultrasound data are acquired from a region-of-interest in a subject who has been administered a microbubble contrast agent. The ultrasound data are acquired while the microbubbles are moving through, or otherwise present in, the region-of-interest. The region-of-interest may include, for instance, microvessels or other microvasculature in the subject. By imaging microbubbles, a cross-correlation map between each microbubble image and a point spread function of the system can be generated. Accumulation of power-based cross-correlation maps may then be used to generate a high-resolution high-contrast image of the microvasculature.

Methods for high spatial and temporal resolution ultrasound imaging of microvessels

Ultrasound attenuation coefficient estimation ('ACE') techniques that can ameliorate frequency power ratio curve oscillations caused by signal interferences, non-uniform tissue structures, or both, are described. The resulting smoothed frequency power ratio curves enable more accurate ACE and reduced region-of-interest (“ROI”) sizes for linear regression.

Systems and methods for ultrasound attenuation coefficient estimation

Described here are systems and methods for improved ultrasound attenuation coefficient estimation ('ACE') techniques. In one aspect, noise can be suppressed by using signal-to-noise ratio (“SNR”) as a quality control metric for restricting depth ranges for ACE. In this way, the proper depth range for each frequency component can be adaptively changed with sufficient SNR for ACE. In another aspect, elevation focusing normalization is used to reduce errors associated with diffraction effects when estimating attenuation coefficient. In another aspect, methods for suppressing noise in ACE techniques is provided. Noise can be suppressed based on a noise field computed from measurements obtained without ultrasound transmission, based on a unique combination of consecutive image frames, based on singular value decomposition (“SVD”) clutter filtering cutoff values, or combinations thereof.

Systems and methods for estimating acoustic properties in a region-of-interest in a subject or other object being imaged using a reference frequency method ('RFM') is described. Using this RFM technique, ultrasound data acquired at a given frequency are normalized by ultrasound data acquired at different frequencies (e.g., adjacent frequencies or otherwise) in order to provide estimations of the acoustic properties (e.g., attenuation coefficient, a backscatter coefficient, or both) that are independent of the ultrasound system used to acquire the underlying data. For instance, the amplitude of each frequency component can be normalized by a different frequency in the power spectrum to cancel out the system-dependent effects. Because the methods described in the present disclosure are system independent, they can be applied to any transducer geometry (e.g., linear or curved arrays) and using any beam pattern (e.g., focused or unfocused).

Methods for ultrasound system independent attenuation coefficient estimation

Systems and methods for processing data acquired using ultrasound elastography, in which shear waves are generated in a subject using continuous vibration of an ultrasound transducer, are provided. The systems and methods described here can effectively remove motion artifacts associated with vibration of the ultrasound transducer, and can also remove the data sampling misalignment caused when a line-by-line imaging mode is used to acquire data, as is done by many conventional ultrasound scanners. Thus, the systems and methods described here provide techniques for transducer motion correction and for aligning motion signals detected by line-by-line scanning ultrasound systems.

Systems and methods for ultrasound elastography with continuous transducer vibration

Described here are systems and methods for super-resolution imaging with ultrasound in which a Kalman filter-based microvessel inpainting technique is used to facilitate robust super-resolution imaging with limited or otherwise missing microbubble signals. The systems and methods described in the present disclosure can be combined with both local and global microbubble tracking methods.

Systems and methods for Kalman filter-based microvessel inpainting for super-resolution imaging

Systems and methods for performing shear wave elastography using push and/or detection ultrasound beams that are generated by subsets of the available number of transducer elements in an ultrasound transducer. These techniques provide several advantages over currently available approaches to shear wave elastography, including the ability to use a standard, low frame rate ultrasound imaging system and the ability to measure shear wave speed throughout the entire field-of-view rather than only those regions where the push beams are not generated.

System and method for shear wave elastography by transmitting ultrasound with subgroups of ultrasound transducer elements

Methods for processing data acquired using ultrasound elastography, in which shear waves are generated in a subject using continuous vibration of the ultrasound transducer, are described. The described methods can effectively separate shear wave signals from signals corresponding to residual motion artifacts associated with vibration of the ultrasound transducer. The systems and methods described here also provide for real-time visualization of shear waves propagating in the subject.

Shear wave elastography with ultrasound probe oscillation

Systems and methods for super-resolution ultrasound imaging of microvessels in a subject are described. Ultrasound data are acquired from a region-of-interest in a subject who has been administered a microbubble contrast agent. The ultrasound data are acquired while the microbubbles are moving through, or otherwise present in, the region-of-interest. The region-of-interest may include, for instance, microvessels or other microvascuiature in the subject. By isolating, localizing, tracking, and accumulating the microbubbles in the ultrasound data, super-resolution images of the microvessels can be generated.

Methods for super-resolution ultrasound imaging of microvessels

Systems and methods for harmonic shear wave detection using low frame rate ultrasound, or a three-dimensional (3D) volumetric scan, are provided. As one example, spurious motion sources, such as intrinsic tissue motion and waves that are not at the incident wave harmonic frequency, are removed based on a scanning sequence in which repeated acquisitions from a given subvolume occur closely in time so as to render effects of the spurious motions negligible. As another example, sampling frequency and center frequency are selected such that the spurious motion signal spectra do not overlap with aliased shear wave motion spectra, such that the spurious motions can be filtered.

Method for harmonic shear wave detection with a low frame rate ultrasound system

Methods for contrast-enhanced ultrasound imaging that implement coded multi-pulses in each of two or more different transmission events are described. Data acquired in response to the two different transmission events are decoded and combined. In some embodiments, the coded multi-pulses include two or more consecutive Hadamard encoded ultrasound pulses. In other embodiments, multiplane wave pulses can be used. Such multiplane wave pulses can be coded using Hadamard encoding, as one example. In addition, the multiplane wave pulses can be further coded using amplitude modulation, pulse inversion, or pulse inversion amplitude modulation techniques.

Methods for encoded multi-pulse contrast enhanced ultrasound imaging

Described here are systems and methods for imaging blood flow in a subject's vasculature, which may include small blood vessels, using ultrasound without the need for a contrast agent. A locally implemented low-rank matrix decomposition is used together with adaptive cutoff values to provide noninvasive ultrasound blood flow imaging capable of imaging the subject's vasculature with very high spatial and temporal resolution, and without the administration of contrast agents such as microbubble contrast agents. Thus, in some instances the systems and methods can be used to image blood flow in small vessels and tissue microvasculature with high spatial and temporal resolution.

Ultrasound blood flow imaging

Systems and methods for ultrasound imaging using a delay-encoded harmonic imaging ('DE-HI') technique is provided. An ultrasound pulse sequence is coded using temporal delays between ultrasound emissions within a single transmission event. This coded scheme allows for harmonic imaging to be implemented. The temporal time delay-codes are applied temporally to multiple different ultrasound emissions within a single transmission event, rather than spatially across different transmitting elements. The received radio frequency ('RF') signals undergo a decoding process in the frequency domain to recover the signals, as they would be obtained from standard single emissions, for subsequent compounding. As one specific example, a one-quarter period time delay can be used to encode second harmonic signals from each angle emission during a single multiplane wave (&#x201c;MW&#x201d;) transmission event, rather than inverting the polarity of the pulses as in conventional MW imaging.

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Rochester, MN, United States of America

Shigao Chen