Circular Cartesian K-space Sampling for MRI Gradient Power Reduction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face limitations in reducing repetition time (TR) due to power constraints of RF and gradient coils, which can lead to increased data acquisition time and artifacts like banding and motion artifacts, while reducing phase encoding steps may compromise image resolution.
Innovation Solution
A method for acquiring k-space data by sampling a circular Cartesian k-space with pulse sequences that vary the amplitude and duration of phase encoding gradients and readout time based on the phase angle, reducing the power load on gradient coils and allowing for shorter TR without sacrificing image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the repetition time (TR) is reduced in MRI imaging, then the data acquisition time is shortened, but the gradient coil power consumption increases beyond acceptable limits
Solution Approach 1:
The patent transforms the traditional rectangular Cartesian k-space sampling path into a circular Cartesian k-space sampling path. This curvature change allows the phase encoding gradient amplitude to vary continuously along the circular trajectory, reducing peak power demands on the gradient coils while maintaining complete k-space coverage for image reconstruction
Solution Approach 2:
The patent implements dynamic adjustment of phase encoding gradient parameters by varying the phase encoding angle φ according to a specific mathematical relationship. The phase encoding gradient amplitude Gp(φ) and duration Δt(φ) are dynamically modified based on the current position in the circular k-space trajectory, enabling adaptive power management throughout the data acquisition sequence
2Loss of time
If the phase encoding steps are reduced to shorten acquisition time, then the data acquisition time decreases, but the image resolution deteriorates
Solution Approach 1:
The patent introduces a temporal dimension to the phase encoding process by continuously varying the phase encoding angle φ over time along the circular trajectory. This transforms the traditional discrete step-wise phase encoding into a continuous angular progression, effectively adding a temporal component that allows for optimized sampling density without reducing the total number of phase encoding steps
3Productivity
If the repetition time (TR) is reduced, then the imaging efficiency improves, but artifacts such as banding and motion artifacts increase
Solution Approach 1:
The patent systematically changes multiple parameters simultaneously: the phase encoding gradient amplitude Gp(φ), the phase encoding gradient duration Δt(φ), and the readout gradient amplitude Gx(φ) are all adjusted as functions of the phase encoding angle φ. This coordinated parameter modulation maintains optimal signal characteristics throughout the reduced TR sequence, suppressing artifact formation while preserving imaging efficiency
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
This approach effectively reduces the repetition time and gradient coil power consumption while maintaining image quality, as demonstrated by MRI images acquired with the circular Cartesian k-space method showing comparable quality to those from rectangular k-space images but with improved efficiency.
Implementation Method 1
gradient coils that produce smaller amplitude, spatially-varying magnetic fields with orthogonal axes to spatially encode the magnetic resonance (MR) signal by creating a signature resonance frequency at each location in the body
Implementation Method 2
gradient coils that produce smaller amplitude, spatially-varying magnetic fields with orthogonal axes to spatially encode the magnetic resonance (MR) signal by creating a signature resonance frequency at each location in the body
Implementation Method 3
As the nuclear spins relax back to their rest energy state, they release the absorbed energy in the form of an RF signal. This RF signal (or MR signal) is detected by one or more RF coils and is transformed into the image using reconstruction algorithms
Data Source
AI summary
Various methods and systems are provided for acquiring k-space data for magnetic resonance imaging. In one example, after applying a phase encoding gradient, the k-space data of a phase angle is acquired while applying a frequency encoding gradient. An amplitude of the phase encoding gradient and a duration of the phase encoding gradient determined based on each and every of a phase angle of the phase encoding line and a duration of the frequency encoding gradient.