Abstract: Systems and methods for magnetic resonance elastography (MRE) are disclosed. In one embodiment, MRE data corresponding to mechanical waves in tissue of interest of a subject is acquired. The MRE data is associated with stiffness of the tissue. The method also includes generating, based on the MRE data, a stiffness map representing stiffness of the tissue. Generating the stiffness map includes performing an unconstrained optimization cost function that is configured to reduce noise in the acquired MRE data and achieve inversion of the reduced-noise data.

Abstract: A method of obtaining analytical expressions for an optimized diffusion encoding gradient (DEG) waveform is disclosed. The method uses a constrained numerical optimization to obtain an optimal configuration of a DEG waveform. The optimization adjusts parameters for a waveform modeled as a finite set of square pulses to maximize an exact b-value equation, while maintaining a waveform shape that also compensates for motion. The optimal configuration is then verified using a waveform model of a set of trapezoidal pulses to obtain an optimal DEG waveform. Generally, the parameters describing the reduced set of trapezoidal pulses are reduced, thereby allowing the optimal DEG waveform to be expressed as closed-form analytical expressions. The analytical expressions simplify the derivation of optimal DEG waveforms for a range of diffusion imaging scanning parameters, thereby improving the quality and versatility of diffusion weighted MRI.

Abstract: Systems and methods are described for inducing tissue vibration for magnetic resonance elastography is described. The system includes a hydraulic drive component that is mechanically linked to a pneumatic drive component. The pneumatic drive component is pneumatically linked to a passive pneumatic actuator component that is positionable on a patient proximate to a target tissue. Alternating linear movement of an actuator piston within the passive actuator component induces vibration of the target tissue. The frequency of the alternating linear movement of the actuator piston within the passive pneumatic actuator component is controlled by adjusting how fluid is pumped in the hydraulic drive component.

Abstract: Systems and methods for magnetic resonance elastography (MRE) are disclosed. In one embodiment, MRE data corresponding to mechanical waves in tissue of interest of a subject is acquired. The MRE data is associated with stiffness of the tissue. The method also includes generating, based on the MRE data, a stiffness map representing stiffness of the tissue. Generating the stiffness map includes performing an unconstrained optimization cost function that is configured to reduce noise in the acquired MRE data and achieve inversion of the reduced-noise data.

Abstract: A method of obtaining analytical expressions for an optimized diffusion encoding gradient (DEG) waveform is disclosed. The method uses a constrained numerical optimization to obtain an optimal configuration of a DEG waveform. The optimization adjusts parameters for a waveform modeled as a finite set of square pulses to maximize an exact b-value equation, while maintaining a waveform shape that also compensates for motion. The optimal configuration is then verified using a waveform model of a set of trapezoidal pulses to obtain an optimal DEG waveform. Generally, the parameters describing the reduced set of trapezoidal pulses are reduced, thereby allowing the optimal DEG waveform to be expressed as closed-form analytical expressions. The analytical expressions simplify the derivation of optimal DEG waveforms for a range of diffusion imaging scanning parameters, thereby improving the quality and versatility of diffusion weighted MRI.

Abstract: Systems and methods are provided for CT-based elastography. A CT gantry is rotated while acquiring CT image data at a first frequency while tissue vibration is induced at a second vibrational frequency. The data acquisition frequency and the vibrational frequency are harmonically related and are synchronized such that the vibrational period aligns with the data acquisition period. Displacement of each of a plurality of tissue points are calculated in each of a series of images and a displacement map is generated demonstrating relative tissue stiffness.

Abstract: Techniques for co-imaging tissue stiffness and blood flow using a single MRI scan are disclosed. The methods use a combined gradient waveform that provides adequate sensitivity for concurrent encodings of flow and tissue stiffness. During a scan, the application of the combined gradient waveform, in the presence of an applied oscillatory motion, simultaneously encodes both flow and stiffness information into the phase of the resulting MRI image. To separate the flow information from the tissue displacement caused by the oscillatory motion, a Fourier transform applied along the direction of applied oscillatory motion. After the transformation, baseband information (flow velocity) may be separated from modulated information (tissue displacement). The separated data may be used to create a velocity map and a displacement map, which can then be converted to a stiffness map.

Abstract: Systems and methods are described for inducing tissue vibration for magnetic resonance elastography is described. The system includes a hydraulic drive component that is mechanically linked to a pneumatic drive component. The pneumatic drive component is pneumatically linked to a passive pneumatic actuator component that is positionable on a patient proximate to a target tissue. Alternating linear movement of an actuator piston within the passive actuator component induces vibration of the target tissue. The frequency of the alternating linear movement of the actuator piston within the passive pneumatic actuator component is controlled by adjusting how fluid is pumped in the hydraulic drive component.

Abstract: A method for magnetic resonance elastography (“MRE”) is described, in which an MRE inversion that accounts for waves propagating in a finite, bounded media is employed. A vibratory motion is induced in a subject and MRE is performed to measure one or more components of the resulting displacement produced in the subject. This displacement data is subsequently filtered to provide a more accurate and computationally efficient method of inversion. Wave equations based on the geometry of the bounded media are then utilized to calculate the material properties of the subject. Such a method allows for the performance of MRE on tissues such as the heart, eye, bladder, and prostate with more accurate results.

Abstract: A system for inducing tissue vibration for magnetic resonance elastography is described. The system includes a passive actuator component, a first hose, a second hose, and a driving component. The passive actuator component is positionable proximate to a target tissue and includes a linearly movable piston assembly enclosed in a housing. The driving component includes a fluid pumping system and is configured to alternatingly pump a fluid through the first hose and through the second hose. When fluid is pumped through the first hose, the piston assembly moves in a first linear direction and, when fluid is pumped through the second hose, the piston assembly moves in the opposite direction. The alternating linear movement of the piston assembly induces vibration in the target tissue.

Abstract: A system for inducing tissue vibration for magnetic resonance elastography is described. The system includes a passive actuator component, a first hose, a second hose, and a driving component. The passive actuator component is positionable proximate to a target tissue and includes a linearly movable piston assembly enclosed in a housing. The driving component includes a fluid pumping system and is configured to alternatingly pump a fluid through the first hose and through the second hose. When fluid is pumped through the first hose, the piston assembly moves in a first linear direction and, when fluid is pumped through the second hose, the piston assembly moves in the opposite direction. The alternating linear movement of the piston assembly induces vibration in the target tissue.

Abstract: A method for magnetic resonance elastography (“MRE”) is described, in which an MRE inversion that accounts for waves propagating in a finite, bounded media is employed. A vibratory motion is induced in a subject and MRE is performed to measure one or more components of the resulting displacement produced in the subject. This displacement data is subsequently filtered to provide a more accurate and computationally efficient method of inversion. Wave equations based on the geometry of the bounded media are then utilized to calculate the material properties of the subject. Such a method allows for the performance of MRE on tissues such as the heart, eye, bladder, and prostate with more accurate results.