MRI Center Frequency Monitoring for Field Decay
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Solution Overview
Problem
Low-field MRI systems require more frequent ramping due to their narrower magnetic field decay window, leading to increased maintenance needs and potential downtime.
Innovation Solution
The method involves continuously monitoring the center frequency of the main magnetic field during patient scans, recording these frequencies, and analyzing them to identify decay-related characteristics. This data is used to derive a calibration factor for the current sensor, improving the accuracy of ramp-up sequences and extending the magnetic field decay window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the target frequency is set to the highest possible value to extend the decay window, then the time between ramping operations is extended, but the magnetic field decays faster in low-field systems due to narrower bandwidth, requiring more frequent ramping
Solution Approach 1:
The patent implements continuous monitoring of the center frequency during patient scans and uses this feedback to detect magnetic field decay. The system records center frequencies from successive scans and analyzes them to identify decay-related characteristics, enabling timely detection of field drift without requiring more frequent manual intervention or ramping operations.
Solution Approach 2:
The monitoring system utilizes existing operational data (center frequencies from patient scans) to automatically detect and report magnetic field decay. This self-monitoring capability eliminates the need for separate dedicated measuring devices or manual service checks, allowing the system to service itself by identifying when maintenance is needed based on its own operational parameters.
2Measurement precision
If dedicated measuring devices are added to monitor magnetic field decay, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent repurposes the existing body coil and receiver, which are already part of the MRI system's imaging functionality, to also serve as monitoring devices for magnetic field decay. The center frequency identification unit extracts frequency information from signals already being processed for imaging, making the imaging components perform dual functions without adding dedicated measuring hardware.
Solution Approach 2:
The system uses its own operational signals (center frequencies from patient scans) to monitor its own magnetic field stability. This self-monitoring approach eliminates the need for external or dedicated measurement devices, reducing system complexity while maintaining measurement capability through intelligent data analysis of existing operational parameters.
3Duration of action of stationary object
If the bandwidth of the body coil is increased to accommodate faster decay, then the decay window is extended, but the system becomes less suitable for low-field applications where bandwidth is inherently limited
Solution Approach 1:
The patent changes the monitoring approach from relying on bandwidth expansion to using continuous frequency parameter tracking. By monitoring center frequency shifts over time and analyzing decay characteristics from successive scans, the system adapts to the limited bandwidth of low-field systems while still effectively detecting magnetic field decay through temporal parameter analysis rather than spectral expansion.
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 effective monitoring of the main magnetic field decay without additional dedicated measuring devices, enabling timely maintenance scheduling and reducing downtime in low-field MRI systems.
Implementation Method 1
the centre frequency of the main magnetic field remains above the body coil centre frequency
Implementation Method 2
the target frequency (i.e. the centre frequency of the main magnet) is determined
Implementation Method 3
In any superconducting MRI system, decay of the magnetic field is unavoidable due to the residual electrical resistance of the magnet
Implementation Method 4
decay of the magnetic field is unavoidable due to the residual electrical resistance of the magnet
Data Source
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AI summary
The invention describes a method of operating an MRI apparatus (1), which method comprises the steps of identifying a centre frequency (fc1, ..., fcn) during successive imaging procedures and recording each centre frequency (fc1, ..., fcn); analysing the centre frequencies (fc1, ..., fcn) to identify a number of decay-related characteristics of the main magnetic field of the MRI apparatus (1). The invention further describes an MRI apparatus (1) and a computer program product for carrying out the steps of the method.