MRI Gradient Slew Rate Control for EPI Imaging
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Solution Overview
Problem
Magnetic resonance imaging (MRI) apparatuses face reduced flexibility in imaging conditions due to decreased output voltage of gradient magnetic field amplifiers, leading to limitations in resolution, extended echo train spacing, and restricted echo numbers, as they struggle to maintain slew rate and waveform consistency during pulse sequences like echo planar imaging (EPI).
Innovation Solution
The MRI apparatus incorporates a sequence control unit that dynamically controls the gradient magnetic field power supply to reduce the slew rate of gradient magnetic field pulses in stages as the output voltage of the gradient magnetic field amplifier decreases, using methods such as RAMP sampling and adjusting pulse sequence execution data to maintain image quality and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If imaging conditions are designed in accordance with the minimum output voltage of the gradient magnetic field amplifier, then the system can operate reliably under all conditions, but the flexibility of imaging conditions is reduced
Solution Approach 1:
The patent applies dynamics by making the slew rate variable rather than fixed. The sequence control unit dynamically adjusts the slew rate of gradient magnetic field pulses based on real-time output voltage levels from the gradient magnetic field amplifier. This allows the system to adapt imaging conditions to match actual amplifier performance, improving both reliability and flexibility simultaneously.
2Measurement precision
If the slew rate is maintained at high levels, then imaging resolution can be improved, but the output voltage of the gradient magnetic field amplifier is reduced and waveform consistency cannot be maintained
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the slew rate parameter based on output voltage measurements. Instead of maintaining a fixed high slew rate that compromises waveform consistency, the system modifies the slew rate parameter in real-time to match amplifier capabilities, thereby maintaining both imaging resolution and waveform consistency.
3Productivity
If a continuous readout gradient magnetic field pulse is applied, then echo planar imaging can be performed, but the output voltage of the gradient magnetic field amplifier is reduced in stages making it difficult to maintain slew rate
Solution Approach 1:
The patent applies feedback by having the sequence control unit monitor the output voltage of the gradient magnetic field amplifier and use this information to adjust subsequent gradient pulse parameters. This closed-loop feedback mechanism ensures that the slew rate is maintained within achievable limits while still enabling continuous readout gradient magnetic field pulse application for echo planar imaging.
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 enhances the flexibility of imaging conditions, improves resolution, prevents echo train spacing extension, reduces distortion, and allows for the use of various gradient magnetic field amplifiers, including less expensive ones, by optimizing the slew rate and waveform of gradient magnetic field pulses in real-time.
Implementation Method 1
a gradient magnetic field amplifier 3a that amplifies a current to be supplied to a gradient coil 2
Data Source
AI summary
A magnetic resonance imaging apparatus according to an embodiment includes a sequence control unit that controls a gradient magnetic field power supply, thereby performing a pulse sequence including the application of a continuous readout gradient magnetic field pulse. The sequence control unit controls the gradient magnetic field power supply such that the slew rate of the gradient magnetic field pulse is reduced in stages as the output voltage of a gradient magnetic field amplifier is reduced in stages.