EPI Magnetic Resonance Slew Rate Control
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Solution Overview
Problem
Conventional magnetic resonance sequences with echo-planar imaging, particularly in echo-planar imaging, experience high noise levels and vibrations due to high slew rates during gradient switchings, which can be distressing for patients and limit examination feasibility.
Innovation Solution
Implementing a magnetic resonance sequence with reduced slew rates in the readout direction, combined with increased echo intervals and segmentation of k-space data entry, to minimize noise and maintain high image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high slew rates are used during gradient switchings in echo-planar imaging sequences, then the magnetic resonance sequence execution is fast and efficient, but loud noises and strong vibrations occur during the examination
Solution Approach 1:
The patent segments the k-space data entry into multiple passes, where each pass acquires a portion of the k-space data at reduced slew rates. This segmentation allows the examination to be divided into manageable sections that can be performed quietly, while still completing the full k-space acquisition necessary for high-quality images.
Solution Approach 2:
The patent changes the slew rate parameter from maximum to reduced levels during gradient switchings. By modifying this critical parameter, the system achieves quieter operation while maintaining acceptable examination speed through optimized sequencing of the gradient pulses and readout windows.
2Loss of time
If high slew rates are used during readout windows, then the echo-planar imaging sequence is completed quickly, but patients with claustrophobia or discomfort are alarmed by loud noises and vibrations
Solution Approach 1:
The examination is segmented into multiple k-space passes, each performed at reduced slew rates. This segmentation extends the total examination time slightly but ensures that no single phase generates excessive noise or vibration, making the examination tolerable for patients with claustrophobia or noise sensitivity.
Solution Approach 2:
The patent employs periodic gradient pulse activations with reduced slew rates during each k-space pass. By using periodic, controlled gradient switching rather than continuous high-slew-rate switching, the system maintains patient comfort while completing the necessary data acquisition through multiple cycles.
3Power
If maximum slew rates are used, then the magnetic resonance apparatus operates at full capacity, but strong vibrations occur during gradient switchings
Solution Approach 1:
The full k-space acquisition is segmented into multiple passes, allowing the apparatus to operate at reduced power levels during each pass. This segmentation enables the system to complete the full examination without requiring continuous maximum power operation, thereby reducing vibrations and improving stability.
Solution Approach 2:
The patent dynamically adjusts the slew rate parameter during different phases of the examination based on the specific requirements of each k-space pass. This dynamic adjustment allows the system to optimize between power output and vibration generation, completing the examination efficiently while minimizing mechanical disturbances.
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
The approach results in significantly reduced noise levels, improved signal-to-noise ratio, and reduced load on the magnetic resonance apparatus, enabling quieter and more comfortable examinations while maintaining high image quality.
Implementation Method 1
Radio-frequency pulses, in particular excitation pulses, are then transmitted via a radio-frequency antenna unit using suitable antenna devices, that cause nuclear spins of particular atoms to be resonantly excited by these radio-frequency pulses are deflected by a defined flip angle relative to the magnetic field lines of the basic magnetic field
Implementation Method 2
As the nuclear spins relax, radio-frequency signals, known as magnetic resonance signals, are emitted, and are received using suitable radio-frequency antennas and then further processed
Implementation Method 3
gradient fields are activated by a gradient coil unit
Implementation Method 4
the body of a person to be examined, such as a patient, is normally exposed, with a basic field magnet, to a high main magnetic field
Data Source
AI summary
In a method and apparatus for magnetic resonance imaging, a particularly quiet magnetic resonance sequence, uses echo-planar imaging with at least one gradient switching in a readout direction, wherein the at least one gradient switching in the readout direction has a slew rate that is less than a maximum slew rate defined by system specification parameters of the magnetic resonance apparatus.