MRI Correction Device for Dynamic B0 Field Compensation
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Solution Overview
Problem
Existing magnetic resonance imaging (MRI) systems face challenges with dynamic B0 field inhomogeneities caused by eddy currents, particularly affecting fat saturation, leading to artifacts and poor image quality, which existing methods fail to adequately address without increasing acquisition time or altering the magnetic resonance sequence.
Innovation Solution
A correction device intercepts control commands between the sequence unit and transmitter, determining B0 field deviations from eddy currents and replacing spectrally selective radio frequency pulses with substitute pulses when deviations exceed a threshold, using B0 field deviation information and potentially artificial intelligence to ensure accurate fat saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spectrally selective radio frequency pulses are used for fat saturation, then fat saturation is achieved, but B0 field inhomogeneities cause inhomogeneous saturation and artifacts
Solution Approach 1:
The patent applies dynamics by making the radio frequency pulse parameters adaptive rather than static. The system dynamically adjusts the center frequency and bandwidth of spectrally selective pulses based on real-time B0 field measurements. This allows the pulse characteristics to change adaptively to compensate for B0 inhomogeneities, ensuring accurate fat saturation despite field variations.
Solution Approach 2:
The patent implements feedback by measuring the actual B0 field distribution and using this information to adjust subsequent radio frequency pulse parameters. The system continuously monitors B0 inhomogeneities and feeds this information back to modify pulse center frequencies and bandwidths, creating a closed-loop control system that maintains accurate fat saturation.
2Object-affected harmful factors
If pauses are incorporated into the measurement sequence to allow eddy currents to decay, then eddy current effects are reduced, but acquisition time increases
Solution Approach 1:
The patent replaces the mechanical/time-based solution (pauses to allow eddy current decay) with a computational/electronic solution. Instead of waiting for eddy currents to naturally decay, the system calculates their effects and compensates for them by adjusting radio frequency pulse parameters. This substitution eliminates the need for time-consuming pauses while still achieving eddy current compensation.
Solution Approach 2:
The patent applies preliminary action by calculating and compensating for eddy current effects before they significantly impact the imaging process. The system predicts eddy current behavior based on gradient pulse characteristics and pre-adjusts radio frequency pulse parameters to counteract the expected effects, rather than reacting after the damage is done.
3Object-affected harmful factors
If targeted gradient objects are inserted to eliminate eddy currents, then eddy current effects are reduced, but the magnetic resonance sequence is altered
Solution Approach 1:
The patent extracts the eddy current compensation function from the gradient pulse sequence and places it in the radio frequency pulse domain. Instead of modifying gradient pulses with additional targeted objects, the system separates the compensation task and implements it through adjusted radio frequency pulse parameters, leaving the gradient sequence intact and simpler.
4Object-affected harmful factors
If additional gradient pulses are added to compensate for accumulated gradient moment, then eddy currents are reduced, but sequence complexity and acquisition time increase
Solution Approach 1:
The patent changes parameters of existing radio frequency pulses (center frequency, bandwidth) rather than adding new gradient pulses. This parameter adjustment approach achieves eddy current compensation without increasing sequence length or complexity, maintaining imaging efficiency while still correcting for eddy current effects.
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 reduces artifacts and improves image quality by dynamically compensating for B0 field inhomogeneities without altering the MRI sequence, allowing for more efficient imaging with less stringent eddy current limits.
Implementation Method 1
a main magnet generating a B0 field in which the nuclear spins of a patient align
Implementation Method 2
High-frequency pulses at the Larmor frequency excite spins in the B0 field, which can be emitted by a high-frequency coil array. These pulses induce precession in the nuclear spins
Implementation Method 3
Spatial encoding is achieved using gradient pulses, which can be generated, for example, by a gradient coil array within the MRI scanner
Implementation Method 4
Dynamic effects, such as the influence of eddy currents on the B0 field. Eddy currents arise primarily from gradient pulses and therefore depend on the gradient profile
Data Source
Figure 1~2
Figure 3
AI summary
A method for operating a magnetic resonance device (1) during the acquisition of magnetic resonance data within a magnetic resonance sequence with at least one gradient pulse and at least one spectrally selective radio frequency pulse, wherein a control device (6) for converting sequence pulses of the magnetic resonance sequence transmits control commands describing the sequence pulses from a sequence unit (7) of the control device (6) to a transmitter (8) of the magnetic resonance device (1), wherein in a correction device (9) connected between the sequence unit (7) and the transmitter (8), through which the control commands are transmitted: - upon receipt of a control command relating to a gradient pulse, B0 field deviation information taking into account the eddy currents caused by the respective gradient pulse is determined at least for the duration of the gradient pulse,and - upon receipt of a control command describing a spectrally selective high-frequency pulse, it is checked whether a threshold value for permissible B0 field deviations according to the B0 field deviation information is exceeded in an area of interest comprising at least one further layer to be recorded at the time of output of the spectrally selective high-frequency pulse, wherein if the threshold value is exceeded, the spectrally selective high-frequency pulse is replaced by a substitute pulse that at least partially compensates for the effect deviations arising from the B0 field deviations.