MRI Corrective Coils for Magnetic Field Homogenization
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Solution Overview
Problem
Current MRI systems face challenges in achieving uniform and strong magnetic fields, particularly at higher field strengths, due to limitations in air core and ferromagnetic frame designs, which affect image quality and patient accessibility, and are hindered by cryocooler-induced vibrations and the need for cryogenic temperatures.
Innovation Solution
The use of corrective coils and a novel configuration that includes primary and secondary coils, along with a patient positioning system, to enhance magnetic field uniformity and strength, utilizing high-temperature superconducting materials and non-ferromagnetic materials to minimize fringe fields and improve patient accessibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If air core superconducting magnets are used to achieve strong magnetic fields, then field strength is improved, but field uniformity deteriorates due to fringe fields and requires complex corrective measures
Solution Approach 1:
The magnet system is divided into multiple independent coil assemblies (first and second coil assemblies) that can be separately positioned and adjusted. Each coil assembly generates a portion of the total magnetic field, allowing independent optimization and correction of field uniformity in different regions of the imaging space.
Solution Approach 2:
The patent introduces spatial positioning adjustments in multiple dimensions by allowing the coil assemblies to be moved along the bore axis and laterally. This multi-dimensional adjustability enables precise control over the magnetic field distribution and uniformity across the imaging volume without requiring complex internal coil structures.
2Manufacturing precision
If ferromagnetic frame magnets are used to improve field uniformity, then field homogeneity is improved, but patient accessibility deteriorates due to confined bore space
Solution Approach 1:
The invention removes the ferromagnetic frame structure from the magnet design, extracting the field-shaping function and replacing it with adjustable non-ferromagnetic coil assemblies. This elimination of the confining ferromagnetic structure opens up the bore space while maintaining field uniformity through positional adjustment of the coil assemblies.
Solution Approach 2:
The patent changes the physical state and material properties of the magnet system by using non-ferromagnetic materials for the coil assemblies and their supports. This material parameter change eliminates the need for a confining ferromagnetic frame while allowing flexible positioning to achieve the desired field uniformity.
3Strength
If cryogenic cooling systems are used to maintain superconductivity, then magnetic field strength is improved, but mechanical stability deteriorates due to cryocooler-induced vibrations
Solution Approach 1:
The patent replaces the traditional cryogenic liquid helium cooling system with a cryocooler unit that uses mechanical refrigeration. This substitution eliminates the need for liquid helium handling and large vacuum insulation systems, reducing mechanical vibrations and improving the stability of the magnet structure while maintaining superconducting operation.
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
This configuration achieves improved magnetic field uniformity and increased field strengths, enabling better image quality and patient positioning flexibility, while reducing the need for cryogenic temperatures and minimizing mechanical vibrations.
Implementation Method 1
Through use of corrective coils magnetic field lines can be manipulated to improve uniformity and image quality
Implementation Method 2
At cryogenic temperatures, however, the coils effectively have no electrical resistance. Liquid helium is often employed in such cryogenic systems, and the superconducting coils so cooled can conduct large electrical currents and provide a strong magnetic field.
Implementation Method 3
the body of a subject is positioned in a primary field magnet and subjected to a strong, constant magnetic field. Radio frequency signals are applied to the subject, which causes the axes of certain atomic nuclei within the body of the subject, usually hydrogen atomic nuclei, to precess or rotate around axes parallel to the direction of the magnetic field.
Data Source
AI summary
A magnetic resonance imaging configuration and methodology to straighten and otherwise homogenize the field lines in the imaging portion, creating improved image quality. Through use of calibrated corrective coils, magnetic field lines can be manipulated to improve uniformity and image quality. Additionally, when the apparatus is composed of non-ferromagnetic materials, field strengths can be increased to overcome limitations of Iron-based systems such as by use of superconductivity. A patient positioning apparatus and methodology allows multi-positioning of a patient within the calibrated and more uniform magnetic field lines.