Magnetic Resonance Repetition Time Reduction via Gradient Deactivation
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Solution Overview
Problem
Magnetic resonance technology is limited by hardware constraints that restrict short repetition times, making it difficult to achieve desired image contrast and comparability across different systems, especially those with low gradient capacity.
Innovation Solution
The method involves repeating MR scan data acquisition pulses while selectively deactivating gradients in predetermined repetitions to reduce the minimum repetition time, allowing for more flexible selection of repetition times and improved comparability of scans across systems with varying gradient capacities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the balance model is used to fully utilize gradient capacity, then gradient utilization is maximized, but repetition time cannot be shortened below a certain limit
Solution Approach 1:
The patent applies periodic action by alternating between gradient-active repetitions and gradient-free repetitions in a cyclic pattern. The pulse sequence is executed with gradients in some repetitions and without gradients in others, allowing the gradient system to rest periodically and thus reducing the average gradient capacity utilization while maintaining short repetition times.
Solution Approach 2:
The patent uses partial action by not activating gradients in every repetition. Instead of continuously utilizing gradient capacity at maximum level, the system deliberately underutilizes the gradient unit in alternating repetitions, which reduces the mean square gradient field strength and allows shorter repetition times without exceeding hardware limits.
2Manufacturing precision
If short repetition times are used to achieve desired image contrast, then image contrast is improved, but gradient capacity limits are exceeded
Solution Approach 1:
By periodically alternating between gradient-active and gradient-free repetitions, the system can use short repetition times for image contrast optimization while ensuring that the gradient system is not continuously overloaded. The periodic rest periods allow the gradient unit to recover and operate within safe limits.
Solution Approach 2:
The patent changes the operational parameters of the gradient system by varying the gradient activation pattern across repetitions. By dynamically adjusting whether gradients are active or inactive in each repetition, the system optimizes image contrast while controlling gradient capacity utilization to prevent overload.
3Reliability
If different repetition times are used on different magnetic resonance systems, then system-specific hardware limitations are respected, but comparability of scans is reduced
Solution Approach 1:
The patent enhances universality by making the pulse sequence design adaptable to different gradient capacity specifications. The alternating gradient-free repetition approach can be applied universally across systems with varying gradient capabilities, allowing standardized short repetition times to be used on different hardware platforms while maintaining scan comparability.
Solution Approach 2:
By changing the gradient activation pattern parameter rather than the repetition time parameter, the system achieves hardware-specific adaptation without affecting the repetition time. This allows the same repetition time to be used across different systems, maintaining scan comparability while respecting individual hardware limitations through adjusted gradient utilization patterns.
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 enables shorter repetition times without overloading the gradient unit, allowing for comparable scans across systems with low and high gradient specifications, enhancing image contrast and reproducibility.
Implementation Method 1
For spatial encoding, gradient fields are generated by respective gradient coils of a gradient unit in the three spatial directions, x, y and z
Implementation Method 2
Both variables scale with the mean square of the gradient field strength Gi2 on the axes i=x, y, z, and are primarily defined by the utilization and heating of the respective gradient coil, the GPA, and the transformer of the gradient control system
Data Source
AI summary
In a method and magnetic resonance (MR) apparatus for generating scan data of an examination object, radiation of RF pulses, activation of gradients, and reading out of MR signals generated by the radiated RF pulses and the activated gradients occur according to a pulse sequence. The signals that are stored as scan data. Repetition of the pulse sequence activating respective other gradients takes place until all the desired scan data are stored, wherein for determined repetitions, no gradients are activated. By the performance of repetitions in which no gradients are switched, a minimum repetition time, which is restricted by the utilized gradient unit due to hardware limitations thereof, can be further reduced. Thus repetition times can be selected more freely, e.g. according to a desired contrast, including on magnetic resonance systems with a low gradient output.