Gradient Coil Arrangement with External Return Path
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Solution Overview
Problem
Existing gradient coil designs for cylindrical bore MRI systems face limitations in size due to cylindrical configurations, leading to increased power consumption and acoustic noise, and are prone to peripheral nerve stimulation (PNS) due to steep magnetic field gradients over smaller volumes.
Innovation Solution
A gradient coil arrangement with a first portion in the bore and a second portion extending outwardly, featuring primary and shield coils with return current paths outside the bore, optimized using stream functions and spherical harmonics to reduce coil length and minimize noise and PNS, while maintaining gradient field linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If gradient coils are designed with cylindrical configuration inside the bore, then the gradient field can be generated, but the coil length becomes excessive and power consumption increases
Solution Approach 1:
The gradient coil design transitions from a purely cylindrical configuration confined within the bore to a hybrid structure where the return current path extends outside the bore. This dimensional change allows the coil to achieve the necessary gradient field while reducing the active coil length inside the bore, thereby decreasing power consumption and improving cooling efficiency.
2Length of moving object
If gradient coils are designed with cylindrical configuration inside the bore, then the gradient field can be generated, but acoustic noise increases
Solution Approach 1:
The return current path is extracted from the cylindrical bore configuration and positioned outside the bore. This separation removes a significant source of acoustic noise generation from the confined cylindrical space, reducing the overall acoustic noise level while maintaining the gradient field performance.
3Measurement precision
If gradient coils use steep magnetic field gradients over smaller volumes, then imaging resolution is improved, but peripheral nerve stimulation (PNS) increases
Solution Approach 1:
The gradient coil system is segmented into distinct functional regions: the primary gradient field-generating portion within the bore and the return current path outside the bore. This segmentation allows optimization of the gradient field for high resolution imaging while distributing the magnetic field changes over a larger spatial volume, reducing the intensity of induced currents that cause PNS.
4Length of moving object
If gradient coil length is reduced, then the apparatus size is decreased, but gradient field linearity deteriorates
Solution Approach 1:
By extending the return current path outside the bore, the design compensates for the reduced active coil length. This dimensional extension provides additional space for optimizing the current distribution and coil geometry, enabling maintenance of gradient field linearity despite the shorter in-bore coil length.
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 solution allows for a significantly reduced gradient coil length with improved gradient field linearity, reduced acoustic noise, and lower probability of PNS, enhancing imaging capabilities and patient comfort.
Implementation Method 1
at least one coil for generating a gradient magnetic field in the imaging region
Data Source
AI summary
A gradient coil arrangement for use in a magnetic imaging system, the imaging system being for generating a magnetic imaging field in an imaging region provided in a bore. The coil arrangement includes a first portion having a substantially cylindrical shape for positioning in the bore, a second portion extending outwardly from an end of the first portion, the second portion being for positioning outside the bore and at least one coil for generating a gradient magnetic field in the imaging region, the at least one coil having a first part provided on the first portion and a second part provided on the second portion.