Flattened Gradient Coil MRI Design
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Solution Overview
Problem
Conventional gradient coils for MRI systems face challenges in achieving a highly linear magnetic field with minimal current usage, fast slew rate, and large field-of-view while avoiding increased complexity and power requirements.
Innovation Solution
The design incorporates a primary coil with a larger x-direction cross-section than y-direction, accompanied by a shielding coil with a similar shape, where the lower portions of both coils are less curved, allowing for efficient magnetic field generation and reduced stray fields, enabling fewer conductor turns and potentially faster slew rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the diameter of a conventional gradient coil is increased to achieve a large field-of-view, then the field-of-view is improved, but the gradient coil becomes stronger and requires more turns of conductor and/or more current from the power supply
Solution Approach 1:
The gradient coil is divided into two distinct portions: an upper curved portion and a lower flattened portion. This segmentation allows each portion to serve different functions - the upper curved portion maintains field generation efficiency while the lower flattened portion reduces the need for excessive conductor turns, thereby achieving large field-of-view without proportionally increasing conductor quantity
Solution Approach 2:
Different regions of the gradient coil are given different geometric properties. The upper portion maintains curvature for optimal magnetic field generation, while the lower portion is flattened to reduce field strength in specific regions. This local differentiation allows the coil to achieve large field-of-view while controlling the overall field strength to avoid excessive current requirements
2Strength
If the gradient coil is made stronger to produce a stronger magnetic field, then the magnetic field strength is improved, but it becomes much more difficult to achieve a high slew rate
Solution Approach 1:
The gradient coil employs local quality differentiation where the upper curved portion generates strong magnetic fields for imaging quality, while the lower flattened portion produces reduced field strength. This allows the overall system to achieve adequate field strength without requiring the entire coil to be excessively strong, thereby enabling faster slew rates
Solution Approach 2:
By segmenting the coil into upper and lower portions with different geometric characteristics, the patent allows the upper portion to contribute to field strength while the lower portion acts as a built-in flux shunt. This segmentation enables the system to achieve the required magnetic field strength without proportionally increasing the total field strength across the entire coil, thus facilitating higher slew rates
3Strength
If more current from the power supply is used to produce a stronger field, then the magnetic field strength is improved, but the energy consumption and power requirements increase
Solution Approach 1:
The lower flattened portion of the gradient coil creates a region of reduced magnetic field strength that acts as a flux shunt. This allows the upper curved portion to generate the necessary field strength for imaging without requiring proportionally higher current from the power supply, as the flux is partially shunted through the lower portion, reducing overall power requirements
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 enhances the gradient coil's performance by reducing the need for stronger fields and higher currents, allowing for a more efficient and faster magnetic field variation while minimizing eddy currents and maintaining optimal shielding performance.
Implementation Method 1
gradient coils that produce smaller amplitude, spatially varying magnetic fields when a current is applied to them
Implementation Method 2
The shielding coil is configured to reduce the magnetic field created by the primary coil in a region outside of the shielding coil
Data Source
AI summary
A gradient coil and an insert gradient coil for a magnetic resonance imaging system include a primary coil. The primary coil includes an upper primary coil portion and a lower primary coil portion, the lower primary coil portion being less curved in cross-section than the upper primary coil portion. The gradient coil also includes a shielding coil disposed outside of the primary coil. The shielding coil includes an upper shielding coil portion and a lower shielding coil portion, the lower shielding coil portion being less curved in cross-section than the upper shielding coil portion.