Spoiler Gradient Pulse Adaptation for Diffusion MRI Coherence Control
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Solution Overview
Problem
In diffusion imaging, achieving a large range of b values with precise control while suppressing unwanted coherence paths is challenging, especially at small b values, leading to interference artifacts and deviations in diffusion measurements.
Innovation Solution
A method for controlling a magnetic resonance tomography apparatus that involves determining coherences, calculating suppression and implicit spoil moments, and adjusting spoiler gradient pulses to effectively suppress coherence paths, using a processor to optimize spoiler gradient pulse adaptation and ensure precise b value control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diffusion gradient pulses are applied with varying amplitudes to achieve a large range of b values, then the range and precision of b value control is improved, but unwanted coherence paths are not sufficiently suppressed leading to interference artifacts
Solution Approach 1:
The patent calculates the implicit spoil moment from diffusion gradient pulses in advance and determines the required additional spoiler moment before acquisition. This preliminary calculation allows the system to pre-determine the necessary spoiler gradient pulse parameters (amplitude and duration) to suppress unwanted coherence paths while maintaining precise b value control across a large range of b values.
Solution Approach 2:
The patent dynamically adjusts the amplitude and duration of spoiler gradient pulses based on the calculated spoiler moment requirements. By changing the parameters of spoiler gradient pulses (amplitude G_spoiler and duration δ_spoiler) according to the specific b value being measured, the system effectively suppresses coherence paths across the entire range of b values while maintaining measurement precision.
2Object-affected harmful factors
If spoiler gradient pulses are applied to suppress coherence paths, then interference artifacts are reduced, but the complexity of the pulse sequence and gradient control increases
Solution Approach 1:
The patent employs an automated calculation process where the spoiler gradient pulse adaptation processor automatically computes the implicit spoil moment from the diffusion gradient pulses and determines the required spoiler moment. This self-service approach eliminates the need for manual optimization of spoiler gradient parameters, reducing operational complexity while maintaining effective coherence path suppression.
Solution Approach 2:
The patent implements a feedback mechanism where the calculated implicit spoil moment from diffusion gradient pulses feeds into the determination of required spoiler moments. This feedback loop allows the system to automatically adjust spoiler gradient parameters based on the actual diffusion gradient configuration, simplifying the overall control process while ensuring effective suppression of unwanted coherence paths.
3Measurement precision
If the amplitude of diffusion gradient pulses is increased to achieve higher b values, then the maximum b value is improved, but the time duration for achieving the same b value is reduced
Solution Approach 1:
The patent employs dynamic adjustment of gradient pulse parameters where the amplitude and duration of both diffusion and spoiler gradient pulses are optimized based on the target b value. This dynamic approach allows the system to achieve high b values with appropriately reduced time durations, maintaining measurement precision while adapting to the specific requirements of each b value in the sequence.
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 allows for precise control of b values, effectively suppressing unwanted coherence paths and minimizing interference artifacts, thereby improving the accuracy of diffusion imaging, particularly for Intra-Voxel Incoherent Motion (IVIM) imaging.
Implementation Method 1
after the usual deflection of the nuclear spins in a plane transverse to the basic magnetic field of the magnetic resonance scanner, a specific sequence of gradient magnetic field pulses (diffusion gradient pulses) is applied
Implementation Method 2
a specific sequence of gradient magnetic field pulses (diffusion gradient pulses) is applied, which vary the field strength of the external magnetic field in a predetermined direction
Implementation Method 3
If a diffusion movement is present, the precessing nuclei fall out of phase, which makes itself noticeable in the measurement signal
Implementation Method 4
an adaptation of spoiler gradient pulses takes place... with which an improved control of a magnetic resonance tomography apparatus for diffusion imaging is achieved... effectively suppressing unwanted coherence paths
Data Source
AI summary
In a method and magnetic resonance tomography apparatus for diffusion imaging, coherences are determined in a processor, which would occur during the diffusion imaging measurement, and an implicit spoil moment MA resulting from a diffusion gradient pulse is determined in the processor. A spoiler moment MS is established in the processor as a function of a comparison value and threshold value formed from the implicit spoil moment MA and the suppression moment M. Depending on whether this comparison value lies below or above the threshold value, different calculation techniques are applied for the spoiler moment MS. Diffusion gradient pulses and spoiler gradient pulses in accordance with the moments MA and MS in a pulse sequence for operating the magnetic resonance tomography apparatus.