Leland Stanford Junior University

Murat Aksoy

Roland Bammer

Julian Maclaren

Melvyn B Ooi

Ronald D Watkins

Chunlei Liu

Rexford Newbould

Jakob Ehrl

Christoph Forman

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

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

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

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

A method of correcting for motion in magnetic resonance images of an object detected by a plurality of signal receiver coils comprising the steps of acquiring a plurality of image signals with the plurality of receiver coils, determining motion between sequential image signals relative to a reference, applying rotation and translation to image signals to align image signals with the reference, determining altered coil sensitivities due to object movement during image signal acquisition, and employing parallel imaging reconstruction of the rotated and translated image signals using the altered coil sensitivities in order to compensate for undersampling in k-space.

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Menlo Park, CA, United States of America

Murat Aksoy