Rotatable Halbach Dipole Rings for Variable MPI Selection Fields
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Solution Overview
Problem
Existing MPI devices cannot generate a selection magnetic field with variable gradient and field-free line, limiting the flexibility and precision of magnetic particle imaging.
Innovation Solution
A magnet arrangement comprising two pairs of Halbach dipole rings, rotatable about a common axis, allows for the generation of a magnetic field with a field-free line and adjustable gradient by varying the angular positions and distances of the rings, enabling flexible selection field generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single pair of Halbach rings is used to generate the selection magnetic field, then the device structure is simple, but the gradient and field-free line cannot be varied
Solution Approach 1:
The magnet arrangement is divided into multiple independent pairs of Halbach rings (first pair and second pair), each pair capable of generating its own magnetic field. This segmentation allows each pair to be independently controlled and positioned, enabling variable gradient and field-free line configuration while maintaining manageable structural complexity through modular design
Solution Approach 2:
The Halbach rings are made rotatable about the common Z axis, introducing dynamic adjustability to the system. By varying the angular positions of the rings, the gradient magnitude and field-free line characteristics can be continuously changed, transforming a static structure into a dynamically adaptable imaging system
2Measurement precision
If the gradient magnitude is increased to improve imaging precision, then the field-free line becomes sharper, but the drive field amplitude must be increased causing nerve stimulation and tissue heating
Solution Approach 1:
Instead of increasing drive field amplitude to achieve sharper field-free line, the invention changes the magnetic field configuration parameters by adjusting the angular positions and distances of the Halbach ring pairs. This allows optimization of the gradient field geometry to achieve sharp field-free line definition with lower overall field amplitudes, reducing harmful effects on the object
Solution Approach 2:
The magnet arrangement is configured to concentrate magnetic field gradient strength specifically at the field-free line region while maintaining lower field amplitudes in surrounding areas. By optimizing the local field distribution through precise positioning of the Halbach rings, high precision is achieved at the measurement point without proportionally increasing the overall energy input that causes heating and stimulation
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 more precise and variable generation of MPI selection fields, reducing the required drive field amplitude and minimizing adverse effects on the object, such as nerve stimulation and tissue heating, while allowing for multiple imaging modes like MRI and CT.
Implementation Method 1
a magnet arrangement which is designed to generate an MPI magnetic field with a gradient B1 and a field-free line in the sample volume
Implementation Method 2
a pair of magnet rings with two magnet rings in a Halbach dipole configuration
Data Source
AI summary
An MPI imaging device for mapping an object to be examined in a sample volume, with a magnet arrangement which is designed to generate an MPI magnetic field with a gradient B1 and a field-free line in the sample volume, the magnet arrangement comprising a first pair of magnet rings with two magnet rings in a Halbach dipole configuration, which are arranged coaxially on a common Z axis that runs through the sample volume, wherein the magnet arrangement comprises a second pair of magnet rings with two further magnet rings in a Halbach dipole configuration, which is arranged coaxially in relation to the first pair of magnet rings, the magnet rings of both pairs being arranged rotatably with respect to one another about the Z axis. As a result, a variable MPI selection field can be generated by means of permanent magnets.