Dixon MR Gradient Timing for Quieter Water-Fat Separation
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Solution Overview
Problem
Conventional Dixon-type MR imaging methods with dual- or multi-acquisition sequences are limited by restrictions on echo times, leading to increased acoustic noise and scan time, which affects patient comfort and imaging efficiency.
Innovation Solution
A method that adjusts the timing and strength of magnetic field gradients in a dual- or multi-acquisition MR imaging sequence to minimize acoustic noise by shifting and stretching specific gradient lobes, using an MR device-specific acoustic transfer function to optimize gradient arrangements, allowing for flexible echo times and reduced noise levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Dixon-type MR imaging methods with dual- or multi-acquisition sequences are used, then water/fat separation is achieved, but acoustic noise increases and scan time increases
Solution Approach 1:
The patent applies dynamics by making the gradient lobes temporally flexible - they can be shifted and stretched dynamically between different time intervals (TR periods) based on acoustic noise modeling. This allows the sequence to adapt its gradient timing to minimize acoustic resonance while maintaining the water/fat separation capability through appropriate echo time selection.
Solution Approach 2:
The patent changes temporal parameters of the magnetic field gradients (timing, duration, amplitude) between different time intervals to minimize acoustic noise. By varying these parameters based on an established acoustic noise model, the system optimizes the balance between image quality (water/fat separation) and patient comfort (noise reduction).
2Measurement precision
If conventional Dixon-type MR imaging methods with dual- or multi-acquisition sequences are used, then water/fat separation is achieved, but scan time increases
Solution Approach 1:
The patent uses dynamic adjustment of gradient timing and echo times between different acquisitions to optimize scan efficiency. By flexibly timing the gradient lobes and echoes, the method can achieve water/fat separation with fewer or more efficient acquisitions compared to conventional fixed sequences.
Solution Approach 2:
The patent optimizes scan time by changing temporal parameters (echo times, gradient durations, repetition times) based on acoustic noise modeling. This allows for more efficient sequence design that reduces total scan time while maintaining the necessary echo time differences for water/fat separation.
3Productivity
If magnetic field gradients are switched in conventional sequences, then imaging is performed, but acoustic noise is generated
Solution Approach 1:
The patent converts the harmful acoustic noise from gradient switching into a design constraint that guides sequence optimization. By modeling the acoustic noise and using it to inform gradient timing decisions, the method transforms a harmful side effect into a basis for optimizing both patient comfort and imaging efficiency.
Solution Approach 2:
The patent applies preliminary action by pre-modeling the acoustic noise characteristics and using this model to determine optimal gradient timing before actual imaging. The established relationship between gradient arrangement and acoustic noise level allows for noise-minimized sequence design from the outset.
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
Reduces acoustic noise and discomfort for patients, while maintaining effective water/fat separation and improving imaging efficiency by minimizing noise generated by magnetic field gradient switching.
Implementation Method 1
The magnetic field B0 produces different energy levels for the individual nuclear spins in dependence on the magnetic field strength which can be excited (spin resonance) by application of an electromagnetic field (RF field) of defined frequency (Larmor frequency)
Implementation Method 2
acoustic noise caused by the switching of the magnetic field gradients
Data Source
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AI summary
The invention relates to a method of Dixon-type MR imaging. The object (10) is subjected to a dual- or multi-acquisition imaging sequence comprising a series of temporally equidistant RF pulses. An echo signal is generated in the presence of a readout magnetic field gradient in each time interval (TR) between successive RF pulses, with the echo time varying between at least a first value (TE1) associated with a first acquisition (ACQ1) and a second value (TE2) associated with a second acquisition (ACQ2). The invention proposes that at least one of the magnetic field gradients preceding and/or succeeding the readout magnetic field gradient in each time interval (TR) is temporally shifted, varied in duration and/or varied in amplitude between time intervals (TR). In this way, a reduction of the acoustic noise generated by the multi-acquisition Dixon sequence and, thus, of the discomfort for patients undergoing a corresponding examination is achieved. The echo signals are recorded and an MR image is reconstructed with separating signal contributions from water and fat based on the recorded echo signals of the at least two acquisitions (ACQ1, ACQ2). Moreover the invention relates to an MR device (1) and to a computer program to be run on an MR device (1).