MRI Gradient Pulse Waveform Design for Silent Imaging
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Solution Overview
Problem
Current MRI techniques fail to achieve almost silent imaging without extending imaging time, are limited to three-dimensional imaging, and cannot set echo time optionally, especially when using gradient magnetic fields with trapezoidal waveforms and smoothened pulses.
Innovation Solution
Employing gradient pulses with a basic waveform where strength dwindles substantially as frequency increases from zero, optimizing application time and strength to reduce noise levels to 6 dB or less, allowing for silent two-dimensional and three-dimensional imaging with optional echo times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gradient magnetic fields with trapezoidal waveforms are used, then imaging speed is improved, but sound production increases to 80-100 dB
Solution Approach 1:
The patent applies parameter changes by modifying the waveform shape of gradient magnetic fields from trapezoidal to sine-waveform. This changes the frequency distribution characteristics of the gradient pulses, shifting energy to lower frequencies where the system's frequency response function is smaller, thereby reducing sound production while maintaining imaging speed.
Solution Approach 2:
The patent employs periodic sine-waveform gradient pulses instead of abrupt trapezoidal switching. The sinusoidal variation provides smooth periodic transitions that reduce high-frequency components responsible for loud acoustic noise, while maintaining the necessary gradient strength for rapid imaging.
2Object-generated harmful factors
If low-pass filter is used to suppress frequency components above 200 Hz, then sound is reduced, but imaging time is extended
Solution Approach 1:
Instead of using a low-pass filter that would extend imaging time, the patent changes the waveform parameter to sine-waveform. This inherently distributes energy to lower frequencies without requiring external filtering, thus reducing sound while avoiding time extension.
Solution Approach 2:
The patent substitutes the mechanical filtering approach (low-pass filter) with a waveform design approach (sine-waveform gradient pulses). This eliminates the need for additional filtering hardware and the associated time penalties while achieving the same sound reduction goal.
3Object-generated harmful factors
If radial three-dimensional imaging method is used to eliminate gradient field on/off, then sound is suppressed, but echo time cannot be set optionally and imaging time increases by 10%
Solution Approach 1:
The patent changes the waveform parameter to sine-waveform for conventional gradient pulses, which suppresses sound through frequency distribution while preserving the ability to control gradient timing and strength. This maintains adaptability for optional echo time settings unlike the radial method.
Solution Approach 2:
The sine-waveform gradient pulse design is universally applicable to various imaging sequences (2D, 3D, different echo times) while consistently reducing sound. Unlike the radial method which requires specific sequence constraints, this approach works across multiple imaging modalities without limiting versatility.
4Object-generated harmful factors
If smoothened gradient pulses are used at rise and fall time, then sound is reduced, but application time is extended
Solution Approach 1:
The patent applies parameter changes by using sine-waveform throughout the entire gradient pulse duration rather than only smoothening rise and fall times. This distributes energy to lower frequencies across the whole pulse, achieving sound reduction without extending the effective application time.
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 almost silent imaging without extending imaging time, applicable to both two-dimensional and three-dimensional imaging, with the ability to set echo time freely, effectively suppressing sound production across all gradient pulses.
Implementation Method 1
a gradient coil (102) which generates a gradient magnetic field within the static magnetic field
Implementation Method 2
an RF coil (107) which generates an RF magnetic field and detects a nuclear magnetic resonance signal
Implementation Method 3
uses as the gradient pulse included in the predetermined pulse sequence, a gradient pulse which is adjusted using a basic waveform having a distribution of frequencies where strength dwindles substantially as the frequency increases from zero
Data Source
AI summary
In an MRI apparatus, an imaging that produces almost no sound is implemented without extending an imaging time, not only for three-dimensional imaging, but also for two-dimensional imaging. A gradient pulse in a pulse sequence provided in the MRI apparatus is adjusted by using a basic waveform having a distribution of frequencies where strength dwindles substantially as the frequency increases from zero, and the waveform is convex upward or downward varying smoothly. An application time and strength are adjusted so that almost no sound is produced. Any imaging executable by a conventional pulse sequence can be implemented without producing almost any sound, using the conventional pulse sequence with little change.