Leland Stanford Junior University

General Electric Company

Roland Bammer

Murat Aksoy

Julian Maclaren

Stefan Skare

Philip James Beatty

Anja C S Brau

Norbert Joseph Pelc

Michael Markl

Chunlei Liu

Melvyn B Ooi

Greg Zaharchuk

Michael E Moseley

Burak Acar

Anh Tu Van

Benjamin Zahneisen

Ronald D Watkins

Michael Mosley

Rafael O'Halloran

Rexford Newbould

Jakob Ehrl

Christoph Forman

Matus Straka

Gregory Albers

Methods to quantify motion of a human or animal subject during a magnetic resonance imaging (MRI) exam are provided. In particular, these algorithms make it possible to track head motion over an extended range by processing data obtained from multiple cameras. These methods make current motion tracking methods more applicable to a wider patient population.

Apparatus and method for wide-range optical tracking during medical imaging

Hearing protection combined with head motion tracking for magnetic resonance (MR) procedures is provided. Trackable earplugs include an MR-visible sample combined with a passive resonant circuit. The trackable earplugs act as wireless markers for the MR system. A third wireless MR marker can be disposed on the forehead of the subject to facilitate motion tracking in six degrees of freedom (i.e., 3 rotations, 3 translations). Preferably, the coordinate system for motion tracking is rotated relative to standard MR coordinates to ensure distinct tracking peaks from the two trackable earplugs.

Devices and methods for trackable hearing protection in magnetic resonance imaging

Devices and methods to measure and visualize the cardiac and respiratory signal of a human or animal subject during a magnetic resonance imaging (MRI) exam are described. This includes a video camera compatible with the MRI scanner, a means of transferring the video data away from the MRI scanner, a light source that illuminates the subject, and an algorithm that analyses the video stream and uses small image intensity changes and motion information to extract cardiac signal and respiratory signals of the subject. These methods make it practical to use optical tracking to monitor and correct for cardiac and respiratory motion during MRI, as well as provide basic patient monitoring with no physical contact to the subject.

Contact-free physiological monitoring during simultaneous magnetic resonance imaging

Improved cross-calibration between magnetic resonance imaging (MRI) coordinates and optical tracking coordinates is provided. Initial calibration is performed with a calibration tool that includes wireless active markers that can be tracked using the MRI scanner, and an optical marker that can be tracked using the optical tracking system. Data from one or more poses of this tool are used to provide an initial cross-calibration. In use, this initial calibration is corrected to account for differences between actual camera position and the reference location. Here the reference location is the camera location at which the initial calibration was performed.

Determination of the coordinate transformation between an optical motion tracking system and a magnetic resonance imaging scanner

Wireless markers having predetermined relative positions with respect to each other are employed for motion tracking and/or correction in magnetic resonance (MR) imaging. The markers are inductively coupled to the MR receive coil(s). The correspondence between marker signals and markers can be determined by using knowledge of the marker relative positions in various ways. The marker relative positions can be known a priori, or can be obtained from a preliminary scan. This approach is applicable for imaging (both prospective and retrospective motion correction), spectroscopy, and/or intervention.

Method for 3D motion tracking in an MRI scanner using inductively coupled microcoils

Improved correction of MRI images is provided making use of three main principles. First, a hybrid representation of the image reconstruction problem is used where the raw MRI data is Fourier transformed in x to provide a x-k-krepresentation. Second, blip-up blip-down acquisition is performed to provide data having equal and opposite regular k-space encoding. Third, joint least squares reconstruction is performed using a singular value decomposition of a joint blip-up, blip-down encoding matrix. The encoding matrix includes at least the effects of regular k-space encoding and known phase variations due to system non-ideality. Preferably, suitable regularization of the encoding matrix based on its singular values is used to automatically remove poorly conditioned parts of the data.

Algebraic reconstruction method for off-resonance and eddy-current correction in functional and diffusion weighted magnetic resonance imaging

A miniature, low-power, optical sensing device that operates in the harsh electromagnetic environment of a magnetic resonance imaging system is provided. The device includes a means of transferring imaging data obtained with the optical sensor out of this harsh electromagnetic environment without requiring a galvanic connection. It is practical to power the device using a small battery that is compatible with the harsh environment. In other embodiments, the device is powered using 'power over fiber' or by taking power by 'power harvesting' directly from the harsh electromagnetic environment. One embodiment is to directly integrate the device into a magnetic resonance imaging (MRI) head coil, using a wired connection to the head coil to provide electrical power. Here the wired connection does not penetrate the Faraday cage of the MRI system or cross into the bore of the MRI system from outside the bore.

Apparatus for obtaining high-quality optical images in a magnetic resonance imaging system

Phase error in MR imaging is corrected in real time by providing adaptive RF pulses and corresponding adaptive magnetic field gradients to mitigate the effect of phase error in the imaging subject. A real time phase error map is obtained, and then adaptive RF pulses and corresponding field gradients are applied that remove the problematic effects of the phase error. Depending on details of the MR imaging mode being employed, there are several ways this removal can be done. Phase error can be cancelled by providing RF pulses that make the phase in the imaging subject uniform. Another approach is to make the adaptive RF pulses insensitive to the phase errors that are present.

Apparatus for real-time phase correction for diffusion-weighted magnetic resonance imaging using adaptive RF pulses

Arterial spin labeling MRI is used to provide a patient specific correction factor to correct a image provided by a non-ASL imaging modality (e.g., DSC MRI). More specifically, a first blood flow image is taken using the non-ASL imaging modality, and a corresponding second blood flow image is taken with ASL. Some or all of the voxels in the first image are selected according to a predetermined selection method. A correction factor (CF) is computed to be the ratio of second image BF to first image BF averaged over the selected voxels. Thus, CF is the average of ASL/non-ASL blood flow over the selected voxels. This correction factor is applied to all voxels of an image equally, but can differ from patient to patient. This correction can be applied to one or more non-ASL blood flow images.

Arterial spin labeling MRI-based correction factor for improving quantitative accuracy of blood flow and volume images

The tracking and compensation of patient motion during a magnetic resonance imaging (MRI) acquisition is an unsolved problem. A self-encoded marker where each feature on the pattern is augmented with a 2-D barcode is provided. Hence, the marker can be tracked even if it is not completely visible in the camera image. Furthermore, it offers considerable advantages over a simple checkerboard marker in terms of processing speed, since it makes the correspondence search of feature points and marker-model coordinates, which are required for the pose estimation, redundant. Significantly improved accuracy is obtained for both phantom experiments and in-vivo experiments with substantial patient motion. In an alternative aspect, a marker having non-coplanar features can be employed to provide improved motion tracking. Such a marker provides depth cues that can be exploited to improve motion tracking. The aspects of non-coplanar patterns and self-encoded patterns can be practiced independently or in combination.

Method for optical pose detection

Automated AIF/VOF identification is useful in connection with providing rapid and automatic quantitative imaging results. Examples include CBF (cerebral blood flow) and CBV (cerebral blood volume) perfusion maps. In the present work, AIF/VOF regions of images are identified by making use of a predefined anatomic vasculature template to provide numerical weighting values for voxels. A score is computed for each voxel that includes normalized signal fit parameters and the numerical weighting. AIF/VOF voxels are identified as N voxels having the highest score, where N can depend on the image resolution.

Automated detection of arterial input function and/or venous output function voxels in medical imaging

In tensor MRI, a set of k-space MRI data points is acquired that includes one or more k-space subsets of MRI data points. An object orientation (or spatial transformation) corresponding to each of the k-space subsets is determined. Because the object orientation (or spatial transformation) can differ from subset to subset, the overall set of k-space data can be inconsistent with respect to object orientation (or spatial transformation). This possible inconsistency can be addressed by providing a k-space tensor model that includes object orientation and/or spatial transformation information corresponding to each of the subsets. A tensor MRI image can be reconstructed from the set of k-space MRI data points by using the k-space tensor model to account for object orientation and/or spatial transformation.

Motion corrected tensor magnetic resonance imaging

The present invention provides a system and method for parallel imaging that performs auto-calibrating reconstructions with a 2D (for 2D imaging) or 3D kernel (for 3D imaging) that exploits the computational efficiencies available when operating in certain data 'domains' or 'spaces'. The reconstruction process of multi-coil data is separated into a &#x201c;training phase&#x201d; and an &#x201c;application phase&#x201d; in which reconstruction weights are applied to acquired data to synthesize (replace) missing data. The choice of data space, i.e., k-space, hybrid space, or image space, in which each step occurs is independently optimized to reduce total reconstruction time for a given imaging application. As such, the invention retains the image quality benefits of using a 2D k-space kernel without the computational burden of applying a 2D k-space convolution kernel.

Method and apparatus of multi-coil MR imaging with hybrid space calibration

Disclosed is a new propeller EPI pulse sequence with reduced sensitivity to field inhomogeneities is proposed. Image artifacts such as blurring due to Nyquist ghosting and susceptibility gradients are investigated and compared with those obtained in previous propeller EPI studies. The proposed propeller EPI sequence uses a readout that is played out along the short axis of the propeller blade, orthogonal to the readout used in previous propeller methods. In contrast to long-axis readout propeller EPI, this causes the echo spacing between two consecutive phase-encoding (PE) lines to decrease, which in turn increases the k-space velocity in this direction and hence the pseudo-bandwidth.

Growing community of inventors

Palo Alto, CA, United States of America

Roland Bammer