Flipped Readout Gradient for MRI Slew Rate
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Solution Overview
Problem
Diffusion-weighted magnetic resonance sequences require extremely high slew rates, making it difficult to achieve short echo times with low-end magnetic resonance devices, resulting in prolonged echo times and compromised image quality.
Innovation Solution
The readout gradient is flipped relative to at least one gradient direction, allowing two gradient coils to contribute to the slew rate, and a constant phase coding gradient is used during the readout time, eliminating steep 'blips' and enabling a higher effective slew rate, thereby reducing echo times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diffusion-weighted magnetic resonance sequences are used with standard gradient coil arrangements, then diffusion weighting is achieved, but echo times become excessively long due to limited slew rates
Solution Approach 1:
The patent applies dimensionality change by flipping the readout gradient direction to utilize contributions from multiple gradient coils (at least two coils) simultaneously, effectively increasing the available slew rate through spatial reconfiguration of the gradient application
Solution Approach 2:
The patent changes the readout gradient direction parameter by flipping it relative to the gradient coil arrangement, transforming the gradient application geometry to achieve higher effective slew rates and shorter echo times while maintaining diffusion weighting capability
2Ease of manufacture
If low-end magnetic resonance devices are used, then device cost is reduced, but echo times are prolonged due to limited slew rates
Solution Approach 1:
The patent modifies the readout gradient direction parameter to flip the gradient application geometry, enabling low-end devices to achieve higher effective slew rates by utilizing multiple gradient coils in combination, thereby reducing echo times without requiring expensive hardware upgrades
Solution Approach 2:
The patent enables gradient coils to serve multiple functions by having at least two gradient coils contribute to the slew rate simultaneously through the flipped readout gradient configuration, allowing standard gradient coil arrangements to achieve performance levels typically requiring specialized high-end hardware
3Speed
If readout gradient is flipped to utilize multiple gradient coils, then effective slew rate increases, but gradient direction alignment becomes complex
Solution Approach 1:
The patent introduces dynamic adjustment of gradient directions by flipping the readout gradient relative to the gradient coil arrangement, allowing the system to adaptively optimize slew rate utilization while maintaining controllable and reversible gradient application geometry
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 allows for a 15% reduction in echo time, enabling clinically significant, higher-quality image data with echo times under 250 ms, even with low-end magnetic resonance devices that typically require longer echo times due to limited slew rates.
Implementation Method 1
For the generation of the gradient pulses a gradient coil arrangement is provided that typically has three gradient coils that each correspond to a different spatial direction in an imaging region, i.e. can generate a gradient of the magnetic field in this gradient direction
Implementation Method 2
Within the scope of a magnetic resonance sequence, nuclear spins in a subject are excited by at least one excitation pulse and the resulting magnetic resonance signals generated by the spins are acquired
Data Source
AI summary
In a method and magnetic resonance apparatus to acquire magnetic resonance data with a diffusion-weighted magnetic resonance sequence wherein the magnetic resonance apparatus as a gradient coil arrangement with three gradient coils designed to generate a gradient in gradient directions orthogonal to one another, the readout gradient is flipped relative to at least one of the gradient directions such that at least two gradient coils contribute to a possible slew rate of a readout gradient pulse, and such that a phase coding gradient that is constant over the readout time period is selected.