Local SAR Calculation via MR B1 Mapping
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Solution Overview
Problem
Current methods for calculating local specific energy absorption rate (SAR) in MRI procedures are time-consuming and not patient-specific, leading to unnecessary safety margins and prolonged acquisition times due to the need for lengthy simulations based on generic human anatomy models.
Innovation Solution
A method that calculates local SAR using pre-determined electric parameters and mass density from segmented geometry and magnetic field vector distribution, estimated through magnetic resonance scanning, eliminating the need for electromagnetic field simulations and providing a patient-specific and rapid estimation of SAR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full electromagnetic field simulation is performed to calculate local SAR, then measurement precision is improved, but loss of time increases significantly (several hours)
Solution Approach 1:
The patent extracts and measures the actual magnetic field distribution (B1-field) directly from the patient's body using MRI techniques, removing the need for time-consuming full electromagnetic simulations. By measuring the actual field instead of simulating it, the method achieves accurate SAR calculation without the several-hour simulation time penalty.
Solution Approach 2:
The patent introduces an intermediary measurement approach using MRI-based B1-mapping techniques to determine the magnetic field distribution. This intermediary measurement serves as a bridge between the complex electromagnetic simulation and the final SAR calculation, providing accurate field data much faster than direct simulation.
2Device complexity
If generic human anatomy models are used for SAR calculation, then device complexity is reduced, but adaptability decreases (not patient-specific)
Solution Approach 1:
The patent performs preliminary patient-specific MRI scanning and B1-mapping measurements before the actual diagnostic scan. This preliminary action captures the individual patient's anatomy and magnetic field distribution, enabling personalized SAR calculation without adding complexity to the main imaging procedure.
Solution Approach 2:
The patent transitions from static generic anatomy models to dynamic patient-specific measurements. By adapting the SAR calculation to each patient's actual magnetic field distribution and anatomy through MRI-based measurements, the system achieves versatility across different patients while maintaining manageable complexity through standardized measurement protocols.
3Reliability
If safety margins are increased due to model uncertainties, then reliability is improved, but productivity decreases (prolonged acquisition time)
Solution Approach 1:
The patent implements a feedback mechanism where actual patient-specific magnetic field measurements are used to adjust and optimize the SAR calculation. This feedback loop eliminates the need for excessive safety margins by providing accurate, patient-specific field data, thereby maintaining reliability while reducing unnecessary acquisition time extensions.
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
Enables quick SAR calculation in clinical settings, reducing acquisition times to a few seconds to minutes, allowing for patient-specific and scanner-specific assessments, and enabling safe diagnostic scans at elevated RF power levels, including those with metallic implants.
Implementation Method 1
MRI uses a powerful magnetic field to align nuclear magnetization of usually hydrogen atoms in water in the body. Radio frequency (RF) fields are used to systematically alter the alignment of this magnetization, causing hydrogen nuclei to produce a rotating magnetic field detectable by a scanner.
Implementation Method 2
Radio frequency (RF) fields are used to systematically alter the alignment of this magnetization, causing hydrogen nuclei to produce a rotating magnetic field detectable by a scanner.
Data Source
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AI summary
A method for calculating a local specific energy absorption rate (SAR) on basis of an electric parameter and the mass density of a segmented geometry of an object and a magnetic field vector distribution of a radio frequency (RF) antenna. The values of the electric parameter and the mass density are pre-determined values, while the magnetic field vector distribution is estimated by a magnetic field mapping method based on a magnetic resonance (MR) scan. The magnetic field mapping method based on a magnetic resonance scan can be a Bi mapping method. The invention also relates to a magnetic resonance system by means of which SAR calculation can be done in a relatively short period of time. The invention also relates to a computer program comprising instructions for calculating a local specific energy absorption rate (SAR) according to the above mentioned method. The SAR calculation used in the above mentioned method, system and program is done in the relatively short period of time and as such is practicable in a clinical setting.