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Method and apparatus for improving the quality of kinematic mr images

Inactive Publication Date: 2007-05-17
SIEMENS MEDICAL SOLUTIONS USA INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This approach reduces image blur and enhances signal-to-noise ratio by ensuring data is collected close to the desired joint position, enabling the acquisition of sharp images of moving joints with improved dynamic representation without the need for mechanical adjustments, thus improving the quality of MR images.

Problems solved by technology

Thus, since it is not advantageous to start and stop the MR imager during the irregular motion of the joint, repetitive MR data subsets are acquired asynchronously as the joint flexes.

Method used

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  • Method and apparatus for improving the quality of kinematic mr images
  • Method and apparatus for improving the quality of kinematic mr images
  • Method and apparatus for improving the quality of kinematic mr images

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third embodiment

[0042] In a third embodiment for implementation of the invention, the phase encoding gradient is alternated between the first and the second position-encoding amplitude during the first swing of the joint. The desired TODs are determined as above for the desired joint angles. Then the data are search for the two lines of data acquired nearest in time to the desired TOD. Because the phase encoding gradient is alternating between step #1 and step #2, these two lines will necessarily have different gradient amplitudes. During the next cycle of joint movement, the phase encoding gradient is alternated between the third and the fourth encoding amplitudes. This implementation of the invention reduces by 50% the number of joint flexions required to obtain images, while losing some time resolution.

fourth embodiment

[0043] In a fourth embodiment for implementation of the invention, the phase-encoding gradient is stepped among three values, #1, #2, and #3, during the first swing of the joint. That is, the repeated group of sequence elements contains three Imaging Modules. The desired TODs are determined as above for the desired joint angles. Then the data are searched (retrospectively sorted) for selecting the three lines of data acquired closest in time to the desired TOD. Because the phase-encoding gradient has the amplitude pattern #1, #2, #3, #1, #2, #3, these three lines will necessarily have three different phase-encoding amplitudes. During the next cycle of joint movement, the phase encoding gradient is stepped among the between the fourth, fifth, and sixth encoding amplitudes. Compared to the first proposed method, this reduces the number of joint flexions required to obtain images by a factor of three. It is clear that this method can be extended to gradient patterns of any length, to f...

fifth embodiment

[0044] In a fifth embodiment for implementation of the invention, the sequence is run multiple times with all of the phase encoding steps during a single flexion of the joint. This gives a “real-time” image without the need to select data using the TOD. These images may exhibit blur because of joint motion during the extended period of time needed to acquire all of the phase encoding lines. In addition, the sequence parameters needed to acquire images so rapidly may lead to poor SNR. In the proposed method, similar additional data are acquired during additional joint flexions. Two enhanced reconstruction methods are then possible. In the first method, the effective TOD (k=0 Fourier line) of each full image MR data set is determined, and these TODs are compared to the goniometer TODs to estimate, by interpolation, the joint angle. Then images from different flexion cycles but nearly the same estimated joint angle can be averaged to improve SNR. A second, and superior method of enhanc...

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Abstract

A method and apparatus for magnetic resonance (MR) imaging of a moving object, and in particular MR imaging by retrospectively selecting and sorting the MR data acquired with the known prior positions of an orthopedic joint. A mechanical apparatus limits the motion of the joint while an optical or electronic apparatus determines the instantaneous articulation position of the joint, for example its rotational angle. Either partial or complete MR data are acquired asynchronously with respect to various positions of joint movement, and the MR data are then retrospectively selected and sorted to form images of the joint at the various articulated positions. This retrospective selecting and sorting allows sharp images to be acquired using MR data acquired over several flexions and extensions of the joint, regardless of the periodicity or velocity of its motion.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to magnetic resonance (MR) imaging, and more particularly relates to a method and apparatus useful for developing high resolution MR images of an object in motion. [0003] 2. Description of the Related Art [0004] It is well known that Magnetic Resonance (MR) images can be degraded by motion during the imaging scan. One particular exemplary application of MR imaging where motion is an issue, is in the field of orthopedics, where physicians find value in viewing not only static images of joints, but also images of the joint while in motion (commonly referred to as “kinematic studies”). In order to provide such images, several devices exist for adjusting and then fixing the position of a joint so as to image it at selected ones of a plurality of different fixed positions. Use of such mechanical devices is undesirable because of the time it takes to repeatedly adjust and then fix the positio...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01V3/00
CPCG01R33/4818G01R33/563G01R33/56325G01R33/56509G01R33/5673
Inventor PURDY, DAVID EMBREY
Owner SIEMENS MEDICAL SOLUTIONS USA INC
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