Dynamic Gradient Rise Time Adjustment for MR Noise Reduction
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Solution Overview
Problem
Magnetic resonance (MR) imaging sequences are often noisy due to rapidly changing gradient fields, which cause distortions and oscillations, leading to increased noise development and patient discomfort.
Innovation Solution
The method involves dynamically adjusting the rise times of gradients with each high-frequency pulse irradiation during MR image data acquisition, optimizing ramp times for each repetition to minimize noise and maintain a constant gradient value only during data acquisition, thereby reducing dB/dt values and noise generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gradient fields are rapidly switched to achieve fast imaging, then imaging speed is improved, but noise development increases due to distortions and oscillations in the gradient coil
Solution Approach 1:
The patent applies dynamics by making the gradient pulse sequence adaptive rather than fixed. The rise times of gradient pulses are dynamically adjusted based on the specific imaging requirements and gradient coil characteristics, allowing optimization of the balance between imaging speed and noise generation for each individual pulse sequence.
Solution Approach 2:
The patent changes the parameter of gradient rise times from fixed values to variable parameters that can be optimized. By adjusting rise times as a variable parameter in the gradient pulse sequence, the system can minimize dB/dt values and reduce noise while maintaining fast imaging capability.
2Object-generated harmful factors
If rise times of gradients are increased to reduce noise, then noise development is reduced, but the minimum repetition time increases
Solution Approach 1:
The patent applies partial action by selecting optimal rise times that are sufficient to reduce noise but not excessively long. The rise times are optimized to achieve the minimum necessary duration to minimize dB/dt values, avoiding unnecessary time extension while still achieving noise reduction.
Solution Approach 2:
The patent optimizes the parameter of rise times to find the optimal balance point. By treating rise time as an adjustable parameter, the system can determine the minimum sufficient duration that achieves noise reduction without unnecessarily increasing the repetition time.
3Duration of action of moving object
If imaging gradients are switched on at the time of excitation to achieve ultrashort echo time, then echo time is reduced, but gradient distances between repetitions become larger
Solution Approach 1:
The patent applies preliminary action by preparing the gradient system in advance for the excitation pulse. By pre-switching imaging gradients to the desired amplitude before the excitation pulse, the system achieves ultrashort echo times while the gradient distances are managed through optimized rise time parameters.
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 significantly reduces noise development, optimizes gradient activity time, and minimizes patient stimulation by reducing dB/dt values, resulting in a quieter and more efficient MR imaging process.
Implementation Method 1
In order to trigger nuclear spin resonances (e.g., nuclear spin signals), high-frequency excitation pulses (e.g., HF excitation pulses) or high-frequency pulses are irradiated into the examination subject, the triggered nuclear spin resonances are measured
Implementation Method 2
rapidly changing gradient fields that result in distortions and oscillations in the gradient coil and the transmission of this energy to the housing
Data Source
AI summary
In a method for image data acquisition using a magnetic resonance system, in order to excite nuclear spin signals, a sequence of high-frequency pulses is irradiated into an examination subject while gradients are simultaneously switched for position encoding of the excited nuclear spin signals. The rise times of the gradients used during the sequence are adjusted dynamically with each high-frequency pulse irradiation.