pTX Transmit Vector SAR Hotspot Reduction
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Solution Overview
Problem
Current magnetic resonance tomography (MRT) systems face challenges in optimizing the specific absorption rate (SAR) distribution during parallel transmit (pTX) operations, leading to safety margin limitations and inefficiencies due to complex patient-specific calculations and anatomical variations.
Innovation Solution
Implementing a local-coil-specific transmit vector B1_H, determined through finite element simulations and calibration measurements, to restrict amplitude and phase combinations for transmit elements, ensuring homogeneous excitation and reducing SAR hotspots, while allowing for patient-specific adjustments and monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If patient-specific SAR calculations are performed for each anatomical variation, then safety is improved, but calculation complexity and time increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating SAR values for multiple standard anatomical models before actual patient examination. These pre-calculated SAR values are stored and can be quickly selected based on the patient's anatomy type, avoiding the need for complex real-time patient-specific calculations while maintaining safety requirements.
Solution Approach 2:
The patent uses copying by creating standardized anatomical models that represent different patient body types. Instead of performing unique calculations for each patient, the system copies and selects from these pre-defined anatomical models, significantly reducing calculation complexity while maintaining adequate SAR safety assessment.
2Reliability
If conservative safety margins are applied to account for anatomical variations, then patient safety is improved, but system efficiency and productivity decrease
Solution Approach 1:
The patent applies local quality by applying different safety margin levels to different anatomical regions and patient types. Instead of using a single conservative safety margin for all cases, the system tailors the safety margins to specific anatomical characteristics, maintaining patient safety while avoiding excessive conservatism that would reduce system efficiency.
Solution Approach 2:
The patent uses parameter changes by adjusting safety margin parameters based on the selected anatomical model and examination conditions. The system dynamically modifies SAR calculation parameters to match the specific clinical scenario, optimizing the balance between safety and efficiency for each case.
3Manufacturing precision
If complex amplitude and phase combinations are used for pTX elements, then excitation homogeneity is improved, but SAR distribution control becomes more difficult
Solution Approach 1:
The patent applies preliminary action by pre-determining optimal amplitude and phase combinations for pTX elements through simulations and measurements. These pre-optimized parameters are stored and directly applied during examinations, achieving excitation homogeneity without requiring complex real-time SAR control calculations.
Solution Approach 2:
The patent uses an intermediary approach by introducing pre-calculated SAR values and standardized anatomical models as intermediaries between the pTX control system and patient-specific anatomical variations. This intermediary layer simplifies the control complexity while maintaining excitation homogeneity across different patient types.
Data Source
AI summary
A method and a magnetic resonance tomography (MRT) system are provided. The MRT system includes a controller configured to store a transmit vector that is established on a local-coil-specific basis. The transmit vector, for a specific local coil, indicates with which amplitudes and phases, transmit elements of the local coil may be controlled by a transmit device. The controller is configured to initiate a patient-specific calibration measurement on a patient to generate patient-specific calibration data representing a field distribution. The controller is also configured to determine deviations in the patient-specific calibration data from the stored transmit vector established on a local-coil-specific basis. The patient-specific calibration data is generated in the patient-specific calibration measurement on the patient and represents a field distribution. An imaging MRT measurement is not allowed if deviations exceed a threshold value, but is otherwise performed and is monitored by a monitoring device.