MRI RF Power Calibration via Reference Object
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Solution Overview
Problem
Magnetic resonance systems face challenges in reliably generating a pure B1+ field due to the geometry and inhomogeneous structure of scanned objects, leading to variations in radiofrequency excitation pulse amplitudes and potential hardware and safety issues, which require frequent and costly calibration and monitoring.
Innovation Solution
A method involving a reference object is used to record and compare magnetic resonance signals to ensure consistent B1+ amplitudes, allowing for adjustment and monitoring of radiofrequency pulses, enabling continuous system operation and reducing calibration costs by using a predetermined reference value for amplitude verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequent calibration and monitoring are performed to ensure reliable operation, then system reliability is improved, but operational costs and time loss increase
Solution Approach 1:
The patent implements preliminary calibration by storing reference values from initial calibration measurements in a database. During subsequent operations, the system automatically compares current measurements against these pre-stored reference values, eliminating the need for frequent manual recalibration while maintaining measurement reliability.
Solution Approach 2:
The system performs self-verification by automatically comparing measurement signals against stored reference values and generating status indicators. This self-monitoring capability allows the system to maintain reliability without requiring continuous external calibration intervention, reducing both time loss and operational costs.
2Reliability
If multiple measuring apparatuses are used to monitor radiofrequency power, then safety and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces a control device as an intermediary that centralizes the comparison and evaluation functions. Instead of distributing complex measurement capabilities across multiple independent apparatuses, the control device receives measurement signals, compares them against reference values, and generates status indicators, thereby simplifying the overall system architecture while maintaining measurement reliability.
Solution Approach 2:
The control device serves multiple functions: it stores reference values, receives measurement signals from measuring apparatuses, performs comparisons, and generates status indicators. This multi-functional approach consolidates what would otherwise require multiple specialized devices, reducing system complexity while maintaining comprehensive monitoring capability.
3Manufacturing precision
If transmitter adjustment is performed to achieve desired B1+ amplitudes, then image quality is improved, but measurement precision requirements increase
Solution Approach 1:
The patent implements feedback by comparing measurement signals against stored reference values and generating status indicators that reflect whether the B1+ amplitude is within acceptable tolerances. This feedback mechanism allows the system to verify transmitter adjustment accuracy without requiring extremely high measurement precision, as the comparison is made against a reference rather than requiring absolute precision.
Solution Approach 2:
The system changes the parameter being measured from absolute B1+ amplitude to a relative deviation from the reference value. By storing reference values from initial calibration and comparing current measurements against these references, the system transforms the measurement task into one of detecting changes rather than measuring absolute values, thereby reducing the required measurement precision while maintaining adjustment accuracy.
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 ensures reliable and economical operation of magnetic resonance systems by maintaining consistent B1+ amplitudes, reducing the need for frequent recalibration and monitoring, and providing uninterrupted documentation of system performance.
Implementation Method 1
By the emission of a radiofrequency excitation pulse (MHz range) (e.g., the B1 field), the spins are rotated (e.g., 'tilted') out of the direction of the base field into another direction.
Implementation Method 2
After the end of the radiofrequency excitation pulse, the nuclear spins return into the direction of the B0 field. This process induces an electrical signal in the receiver coils, which is then used for the image calculation.
Implementation Method 3
The gradient fields lie in the low-frequency range (kHz range) and are locally superimposed on the base field.
Data Source
AI summary
A predetermined reference object is arranged in a scan volume of a magnetic resonance system. In the scope of adjustment measurements, the reference object is respectively exposed by a radiofrequency transmitter antenna to an adjustment pulse. Using at least one radiofrequency receiver antenna, a magnetic resonance signal excited by the respective adjustment pulse in the reference object is respectively recorded. An amplitude of a first test pulse is ascertained with the aid of the magnetic resonance signals recorded in the scope of the adjustment measurements. In the scope of a subsequent test measurement, the reference object is exposed to the first test pulse by the radiofrequency transmitter antenna. A first measurement signal dependent on the amplitude of the first test pulse is recorded during the exposure of the reference object to the first test pulse. Further measures are implemented based on the recorded first measurement signal.