MRI Pulse Sequence With Overlapping Crusher Gradients for Shorter Echo Time
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Solution Overview
Problem
The LASER technique for magnetic resonance spectroscopic imaging requires six refocus pulses, leading to increased echo time (TE), while semi-LASER technique compromises slice characteristics in the axial direction due to lack of gradient field application.
Innovation Solution
A pulse sequence design where first and second crusher gradient fields overlap, reducing echo time (TE) by using two refocus pulses per axis, maintaining high excitation precision and slice characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the LASER technique is used with six refocus pulses, then volume of interest selection precision is improved, but echo time increases and unwanted signal contamination occurs
Solution Approach 1:
The patent combines the crusher gradient fields with the refocus pulse groups by applying them simultaneously during the same time period. This merging of operations allows the sequence to achieve the signal suppression function of crusher gradients while maintaining the precise slice selection of LASER, without requiring separate time periods for each operation, thereby reducing echo time while preserving volume of interest selection precision
Solution Approach 2:
The patent maintains continuous useful action by ensuring that the crusher gradient fields are applied during the time when refocus pulses are already being applied, rather than sequentially. This continuity eliminates idle time and reduces the overall echo time while maintaining the precision benefits of the LASER technique through proper gradient field application
2Loss of time
If semi-LASER is used with four refocus pulses, then echo time is reduced, but slice characteristics deteriorate
Solution Approach 1:
The patent merges the crusher gradient field application with the refocus pulse application, allowing the gradient fields to be applied during the same time period as the refocus pulses. This combination maintains precise slice characteristics by ensuring proper gradient field application during refocusing, while reducing echo time by eliminating sequential timing delays
Solution Approach 2:
The patent optimizes the timing parameters of gradient field application by applying crusher gradients during the refocus pulse time window rather than sequentially. This parameter change in timing arrangement reduces the overall echo time while maintaining adequate gradient strength and duration to preserve slice characteristics through proper spatial encoding
3Measurement precision
If six refocus pulses are transmitted in LASER, then volume of interest selection precision is improved, but device complexity increases
Solution Approach 1:
The patent reduces device complexity by merging the crusher gradient field operations with the refocus pulse operations into a single integrated time window. This combination eliminates the need for separate sequential operations, reducing the overall sequence complexity while maintaining the precision benefits through proper gradient application during the refocus periods
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
The solution shortens echo time (TE) while preserving high excitation precision and slice characteristics, enhancing magnetic resonance spectroscopic imaging efficiency.
Implementation Method 1
a static field magnet 41 configured to generate a static magnetic field
Implementation Method 2
a gradient field coil 43 configured to generate gradient magnetic fields
Implementation Method 3
a transmitter coil 45 configured to transmit radiofrequency pulses
Implementation Method 4
a receiver coil 47 configured to detect magnetic resonance signals
Data Source
AI summary
According to one embodiment, a magnetic resonance imaging apparatus includes processing circuitry. The processing circuitry is configured to design a pulse sequence including a plurality of refocus pulses and a plurality of crusher gradient fields, in such a manner that a first crusher gradient field to be applied after a first refocus pulse group and a second crusher gradient field to be applied before a second refocus pulse group after the first refocus pulse group overlap one another at least partially. The processing circuitry is configured to acquire magnetic resonance spectroscopic signals by executing the designed pulse sequence.