MR Imaging k-Space Sampling Delay for Eddy Current Artifacts
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Solution Overview
Problem
Image intensity variations caused by eddy currents and gradient hysteresis associated with large amplitude gradients used in MR imaging, particularly in ECTRICKS acquisitions, lead to systematic noise and errors in contrast uptake analysis.
Innovation Solution
Implementing a predetermined delay in sampling the center of k-space after sampling peripheral regions, using zero-encoding pulses to maintain the steady state of the MR signal and reduce the effects of eddy currents and gradient hysteresis, thereby minimizing intensity variations across k-space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large amplitude gradients are used to acquire data for peripheral regions of k-space, then imaging speed and temporal resolution are improved, but eddy current and gradient driver hysteresis cause image intensity variations
Solution Approach 1:
The patent applies preliminary action by implementing a delay period after acquiring data from peripheral regions of k-space before sampling the center region. This delay allows eddy currents and gradient driver hysteresis effects to subside before the next center region sampling, preventing these artifacts from contaminating the center k-space data. The delay is predetermined based on the characteristics of the gradient system and is applied systematically throughout the acquisition sequence.
2Measurement precision
If the center of k-space is sampled frequently to improve temporal resolution, then temporal resolution is improved, but intensity variations from preceding peripheral region gradients affect the center region sampling
Solution Approach 1:
The patent applies local quality by implementing different sampling strategies for different regions of k-space. Specifically, the center region is sampled at a different rate and with a delay relative to peripheral regions, while peripheral regions are sampled continuously. This localized adjustment to the sampling scheme for the center region eliminates intensity variations without compromising the overall temporal resolution of the imaging sequence.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Substantially reduces image intensity variations to the intrinsic noise level, improving the accuracy of contrast uptake analysis and reducing ghosting and noise in MR images.
Implementation Method 1
an MRI system having a plurality of gradient coils positioned about a bore of a magnet to impress a polarizing magnetic field
Implementation Method 2
eddy current and gradient driver hysteresis associated with large amplitude gradients used to acquire data for peripheral regions of k-space causes intensity variations
Implementation Method 3
eddy current and gradient driver hysteresis associated with large amplitude gradients
Data Source
AI summary
The present invention provides a system and method of reducing image intensity variations during imaging acquisitions that utilize large encoding gradient pulses that are played out immediately before a center of k-space is sampled. The present invention includes an acquisition and sampling that implements a predetermined delay in sampling prior to sampling the center of k-space. The delay in sampling the center of k-space following sampling of a peripheral region of k-space maintains the steady state of the MR signal and reduces the image intensity variation caused by eddy current and gradient hysteresis. As such, the intensity variations throughout k-space may be reduced substantially and brought closer to the intrinsic noise level of the data acquisition.