Vector Field Camera for MRI Magnetic Field Correction
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) devices face significant challenges in accurately correcting magnetic field imperfections, leading to image artifacts due to main magnetic field inhomogeneities, susceptibility effects, and dynamic field distortions, which existing field cameras inadequately address by only measuring scalar magnetic field values and ignoring orientation.
Innovation Solution
A vector field camera system that measures both the magnitude and orientation of the magnetic field using vector magnetometers, such as optically detected magnetic resonance (ODMR) sensors, and employs real-valued vector spherical harmonics for accurate three-dimensional modeling and correction of magnetic field deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scalar magnetic field sensors are used to measure magnetic field strength, then the measurement system is simple, but the measurement precision is insufficient because orientation information is ignored
Solution Approach 1:
The patent transitions from scalar (one-dimensional) magnetic field sensing to vector (three-dimensional) magnetic field sensing by incorporating orientation measurement capability. This dimensional expansion allows complete characterization of magnetic field deviations including non-z components, thereby resolving the technical contradiction by improving measurement precision through added dimensional information rather than increasing overall system complexity
2Reliability
If conventional field cameras are used that only measure scalar magnetic field values, then the device complexity is low, but the reliability of magnetic field correction is insufficient due to ignored orientation
Solution Approach 1:
The patent replaces conventional scalar magnetic field sensors with vector magnetometers that utilize optically detected magnetic resonance (ODMR) technology. This substitution introduces quantum optical detection methods to replace traditional magnetic sensing, enabling simultaneous measurement of both magnitude and orientation of magnetic field vectors, thereby improving correction reliability while maintaining manageable system complexity through advanced physical principles
3Measurement precision
If vector magnetometers with ODMR are used to measure both magnitude and orientation, then the measurement precision improves, but the use of energy increases
Solution Approach 1:
The patent employs optically detected magnetic resonance (ODMR) which utilizes quantum phase transitions in diamond nitrogen-vacancy centers to detect magnetic field vectors. By exploiting the quantum phase transition between different spin states of electrons in the diamond lattice, the system achieves high-precision vector magnetic field measurement with relatively low energy consumption, as the detection process relies on optical transitions rather than continuous high-power electromagnetic fields
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
The vector field camera system significantly improves imaging quality by accounting for non-z components of the magnetic field, reducing artifacts, and enabling more precise calibration and correction of magnetic field errors, especially in small-bore scanners and devices with non-cylindrical geometries.
Implementation Method 1
vector magnetometers, such as optically detected magnetic resonance (ODMR) sensors
Implementation Method 2
at least one field camera for determining magnetic field information in the imaging region
Data Source
AI summary
A MRI device including a main field unit for establishing a main magnetic field (MF) in an imaging region, a gradient coil assembly for generating a gradient field in the imaging region, a RF arrangement for sending excitation signals to and receiving MR signals from the imaging region, a field camera for determining MF information in the imaging region, the field camera comprising multiple MF sensors arranged at measurement positions enclosing the imaging region, and a controller. The controller is configured to receive sensor data for each measurement positions, from the sensor data, calculate the MF information for the imaging region, and implement a calibration and/or correction measure depending on the MF information. The field camera may be a vector-field camera acquiring vector-valued sensor data describing the MF at each measurement positions three-dimensionally. The controller may determine the MF information to three dimensionally describe the MF in the imaging region.