MRI RF Power Calculation Using B1 Inhomogeneity Maps
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Solution Overview
Problem
Magnetic Resonance Imaging (MRI) apparatuses face challenges in determining the optimal RF level for imaging specific target organs, as the estimated RF level may not be suitable for the target organ, leading to suboptimal imaging results.
Innovation Solution
The MRI apparatus includes processing circuitry that calculates the power of RF magnetic fields required for excitation at specific flip angles in target slices, acquires information on inhomogeneity of the transmission RF magnetic field, and adjusts the RF level based on B1 maps and pixel values to optimize imaging for the target organ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the RF level is estimated based on a broad imaging region such as a chest or abdomen, then the estimation process is simple and quick, but the estimated RF level may not be suitable for the target organ, leading to suboptimal imaging results
Solution Approach 1:
The patent segments the broad imaging region into multiple regions with different B1 inhomogeneity characteristics. Instead of treating the entire chest or abdomen as a single region, the system divides it into regions based on their specific RF field properties, allowing for more accurate RF level determination for each target organ while maintaining efficiency through region-based processing
Solution Approach 2:
The patent applies local quality by determining RF levels based on local B1 map characteristics specific to each target organ region rather than using a global estimation. The system calculates B1 maps for specific regions of interest and uses these localized measurements to set appropriate RF levels, ensuring optimal imaging quality for each specific organ while accounting for local B1 inhomogeneity
2Measurement precision
If the RF level is adjusted to be suitable for a specific target organ, then imaging quality for that organ is optimized, but additional calculations and measurements are required, increasing the complexity and time of the process
Solution Approach 1:
The patent performs preliminary action by acquiring B1 maps and calculating B1 inhomogeneity information before the main imaging sequence. This preliminary measurement allows the system to pre-determine appropriate RF levels for different target organs, so that when actual imaging is performed, the RF levels are already optimized without requiring complex real-time adjustments during the main scan
Solution Approach 2:
The patent uses B1 maps as an intermediary to bridge the gap between broad region estimation and target organ-specific RF level determination. The B1 map serves as a mediator that provides quantitative information about B1 inhomogeneity, which is then used to calculate appropriate RF level adjustments, simplifying the overall process by providing a measurable intermediate parameter
3Measurement precision
If the RF level is adjusted based on B1 map information for different slices, then imaging quality across multiple slices is optimized, but additional RF power calculations for multiple slices are required
Solution Approach 1:
The patent applies parameter changes by using the B1 map information to calculate RF power adjustments for different slices based on their specific B1 inhomogeneity characteristics. The system modifies the RF power parameter for each slice according to its local B1 conditions, allowing optimized imaging across multiple slices while using a systematic approach to manage the complexity of multiple calculations
Data Source
AI summary
According to one embodiment, a magnetic resonance imaging apparatus includes processing circuitry. The processing circuitry calculates power of a first RF magnetic field required for excitation at a first flip angle in a first target slice, acquires information on inhomogeneity of a transmission RF magnetic field for a cross section crossing the first target slice, and calculate power of a second RF magnetic field required for excitation at a second flip angle in a second target slice different from the first target slice for the cross section by using the information and the first RF magnetic field power.