Leland Stanford Junior University

University of California

Marcus Tedrow Alley

Norbert Joseph Pelc

Shreyas S Vasanawala

Albert Hsiao

John Mark Pauly

Rebecca Fahrig

Joseph Yitan Cheng

Michael Lustig

Zhifei Wen

Michael Markl

Processing techniques of volumetric anatomic and vector field data from volumetric phase-contrast MRI on a magnetic resonance imaging (MRI) system are provided to evaluate the physiology of the heart and vessels. This method includes the steps of: (1) correcting for phase-error in the source data, (2) visualizing the vector field superimposed on the anatomic data, (3) using this visualization to select and view planes in the volume, and (4) using these planes to delineate the boundaries of the heart and vessels so that measurements of the heart and vessels can be accurately obtained.

Comprehensive cardiovascular analysis with volumetric phase-contrast MRI

A method for an object in a magnetic resonance image (MRI) system for providing at least one velocity indicative magnetic resonance image (MRI) with motion correction of the object is provided. Velocity encoding gradients in at least one spatial direction are provided from the MRI system. Spatial frequency data resulting from the encoding gradients are acquired through the MRI system. Image signals are provided by the MRI system. Image data resulting from the image signals are acquired through the MRI system. At least one motion corrected and velocity indicative magnetic resonance image is created from the acquired spatial frequency data and image data.

Intrinsic navigation from velocity-encoding gradients in phase-contrast MRI

An imaging system and method combines a magnetic resonance imaging (MRI) system and an x-ray fluoroscopy system such that the two systems have coincident fields of view. X-rays are generated by a stationary anode x-ray tube in which an electron beam is accelerated from a cathode to an anode. In the presence of the static magnetic field of the MRI system, the electron beam is deflected unless it is parallel to the static magnetic field. The x-ray source of the invention contains elements used to steer the electron beam and increase its focusing on the anode. The beam can be steered electrostatically, electromagnetically, or by adding magnetic material to the x-ray source. In the resulting system, MR and x-ray images are acquired without moving the object, which is particularly useful for image-guided medical intervention procedures.

Modified X-ray tube for use in the presence of magnetic fields

A novel technique for velocity measurements (PC-SSFP) is disclosed that combines CINE Phase Contrast (PC) MRI and balanced Steady State Free Precession (SSFP) imaging. Flow encoding is performed without the introduction of additional velocity encoding gradients in order to permit data acquisition with short TR comparable to repetition times of typical SSFP imaging sequences. Sensitivity to through plane velocities is instead established by inverting (i.e. negating) all gradients along the slice select direction. Velocity sensitivity (venc) can be adjusted by altering the first moments of the slice select gradients. Disturbances of the SSFP steady state are avoided by acquiring different flow echoes in consecutively (i.e. sequentially) executed scans, each over several cardiac cycles, using separate steady state preparation periods. Comparison of phantom measurements with those from established 2D-CINE-PC MRI excellent correlation between both modalities. Results of volunteer examinations exhibit advantages of PC-SSFP, which include the intrinsic high signal to noise ratio (SNR) of balanced SSFP and consequently low phase noise in measured velocities. An additional benefit of PC-SSFP is its lower reliance on in-flow dependent signal enhancement, therefore yielding more uniform SNR and better depiction of vessel geometry throughout the whole cardiac cycle in structures with slow and/or pulsatile flow.

Flow imaging using balanced phase contrast steady state free precession magnetic resonance imaging

In a magnetic resonance imaging system, an extended field of view through an object is realized with a magnet having a smaller homogeneous field of view by translating the object through the homogeneous field while exciting nuclear spins within the object and detecting MRI signals with a plurality of coils which translate through the homogeneous field with the object. In a preferred embodiment, the plurality of receiver coils overlap. The table and object can continuously move through the homogeneous volume during nuclear excitation and MRI signal detection. A computer adjusts the MRI signals for the effect of changes in table position between signal acquisitions and compensate for phase shift in received signals.

MRI method apparatus for imaging a field of view which is larger than a magnetic field

Disclosed is an apparatus and a method for three dimensional magnetic resonance data acquisitions using a fast 3D sequence to acquire volumetric data in a cine mode. The entire heart can be imaged in the same amount of time that a conventional cine scan requires for a single section. The true temporal resolution is similar to that of the segmented k-space acquisition. The sequence uses very short repetition times (TR), and hence the inherent contrast is poor. This problem is overcome with the use of a T,shortening agent. Since contrast between blood and the myocardium is no longer flow dependent, it is more stable throughout the heart cycle.

Method for temporally resolved, three-dimensional MR volume acquisitions

Disclosed is a method for characterizing the gradient subsystem of a Magnetic Resonance (MR) system. The method uses a Fourier-transform analysis to directly measure the k-space trajectory produced by an arbitrary gradient waveform. In addition, the method can be easily extended to multiple dimensions, and can be adapted to measuring residual gradient effects such as eddy currents. Several examples of gradient waveform and eddy-current measurements are presented. Also, it is demonstrated how the eddy-current measurements are presented. Also, it is demonstrated how the eddy-current measurements can be parameterized with an impulse-response formalism for later use in system tuning. When compared to a peak-fitting analysis, this technique provides a more direct extraction of the k-space measurements, which reduces the possibility of analysis error. This approach also has several advantages as compared to the conventional eddy-current measurement technique, including the ability to measure very short time constant effects.

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Palo Alto, CA, United States of America

Marcus Tedrow Alley