Direct RF Transmitter for MRI Scanner B1 Field Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic resonance scanners face challenges with load-dependent and frequency-dependent B1 magnetic field amplitudes due to limitations in RF energy transmission and average power, requiring frequent adjustments and calibration, especially when operating beyond resonant frequencies, which affects image quality.
Innovation Solution
A transmitter device with a high-frequency power source directly connected to the transmission coil, eliminating the need for defined characteristic resistance and matching networks, allowing for load-impedance-independent current and constant magnetic field amplitude through a series-resonant coil configuration and λ/4 transformer, enabling broadband operation and automatic adjustment of feed voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional class AB transmitter with defined output resistance and matching network is used, then the transmitter can be designed with standard components, but the B1 magnetic field amplitude becomes load-dependent and frequency-dependent, requiring frequent adjustments
Solution Approach 1:
The patent extracts and eliminates the matching network and defined characteristic resistance from the transmitter design. By directly connecting the high-frequency power source to the transmission coil without intermediate matching components, the system achieves load-impedance-independent current flow, thereby eliminating the need for frequent adjustments while maintaining ease of manufacture
Solution Approach 2:
The patent changes the fundamental impedance parameter from a defined fixed resistance (50Ω) to a load-impedance-independent configuration. This parameter change enables the B1 magnetic field amplitude to remain constant across varying loads and frequencies, resolving the contradiction between standard design and operational stability
2Measurement precision
If the transmission coil is adjusted to resonate at the center of the frequency band, then the B1 magnetic field amplitude is optimized at that frequency, but operation beyond resonant frequency reduces the magnetic field due to reactive incorrect adaptation
Solution Approach 1:
The patent creates a universal feeding configuration that works effectively across a broad frequency range without requiring frequency-specific matching networks. The direct connection approach enables the system to maintain constant magnetic field amplitude whether operating at or beyond the resonant frequency, achieving both precision and versatility
Solution Approach 2:
The patent implements a dynamic system that automatically adapts to frequency changes without manual intervention. By eliminating the fixed impedance matching network and using a high-frequency power source with direct coil connection, the system dynamically maintains optimal performance across varying frequencies and load conditions
3Power
If overdimensioning of the transmitter and power supply is done to compensate for efficiency loss at large pulse duty ratios, then the average output power can be maintained, but the maximum output power and effects on the object to be examined are adversely affected
Solution Approach 1:
The patent replaces the conventional class AB voltage-controlled amplifier with a high-frequency power source that directly generates current. This substitution eliminates the efficiency losses inherent in conventional amplifiers at large pulse duty ratios, maintaining both average and maximum output power without requiring overdimensioning, thereby avoiding adverse effects on the examined object
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 solution ensures a constant B1 magnetic field amplitude across varying loads and frequencies, reducing the need for frequent adjustments and enhancing image quality by maintaining efficiency and power consistency, even at high pulse duty ratios.
Implementation Method 1
a transmission coil for generating a B1 magnetic field
Implementation Method 2
series-resonant coil configuration
Data Source
AI summary
A transmitter device for a magnetic resonance scanner includes a transmitter that is arranged in spatial proximity of a transmission coil that is connected thereto. The transmitter is embodied as a high-frequency power source that is connected directly to the transmission coil.