Multi-purpose Gradient Array for MRI
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Solution Overview
Problem
Conventional MRI systems are inefficient due to the need for high power amplifiers to drive gradient coils, resulting in high power consumption, heat generation, and time-consuming image acquisition, especially when imaging multiple slices.
Innovation Solution
A multi-slice magnetic resonance imaging system featuring a gradient coil array and a controller that generates various field combinations by adjusting current weightings, allowing for simultaneous multi-slice excitation with a single RF pulse, reducing power usage, and optimizing magnetic field distribution for each patient and disease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional MRI systems drive each gradient coil with high power amplifiers to generate linearly changing magnetic fields, then the gradient strength and imaging capability are improved, but the power consumption and heat generation increase significantly
Solution Approach 1:
The patent combines multiple gradient coils (x-gradient, y-gradient, and z-gradient coils) into an integrated gradient system that generates multi-component gradient fields simultaneously. By merging the functionality of separate gradient coils into a unified system with shared power amplifiers, the invention reduces the total number of high-power amplifiers needed while maintaining gradient field generation capability, thereby reducing power consumption and heat generation
Solution Approach 2:
The gradient coils in the invention are designed to perform multiple functions: they generate not only linear gradients for spatial encoding but also non-linear gradients for slice selection and other imaging purposes. This multi-functionality eliminates the need for separate dedicated coils for each gradient component, reducing overall system power requirements
2Ease of operation
If conventional MRI systems acquire images in a slice-by-slice manner using sequential excitation, then the imaging process is simplified, but the total imaging time increases significantly
Solution Approach 1:
The invention employs periodic alternating gradient fields to selectively excite different slices simultaneously. By periodically reversing the polarity of gradient coils and using frequency-selective RF pulses, the system can excite multiple slices in parallel during each RF pulse cycle, dramatically reducing the total number of excitation cycles needed and thus reducing imaging time
Solution Approach 2:
The system applies pre-saturation pulses and gradient pre-phasing to prepare multiple slices for simultaneous excitation before the main imaging sequence begins. This preliminary preparation enables parallel slice excitation without requiring complex real-time adjustments during the imaging process, maintaining operational simplicity while reducing imaging time
3Device complexity
If conventional MRI systems use uniform gradient fields for all slices, then the system configuration is simplified, but the ability to optimize imaging for different patients and diseases is reduced
Solution Approach 1:
The invention implements locally optimized gradient fields where different gradient amplitudes, directions, and waveforms can be applied to different spatial regions and slices. The system can customize gradient parameters for specific regions of interest, patient anatomy, and disease characteristics, allowing tailored imaging protocols without requiring complete system redesign for each application
4Speed
If conventional MRI systems use high amplitude gradient fields to reduce imaging time, then the imaging speed is improved, but the stimulation of peripheral nerves increases
Solution Approach 1:
The invention uses dynamically adjusted gradient waveforms that adapt their amplitude and timing based on the imaging phase and slice being excited. By using time-varying gradient fields with optimized rise times and slew rates, the system achieves fast imaging while keeping gradient amplitudes below the threshold for peripheral nerve stimulation, unlike conventional systems that use constant high-amplitude gradients
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 system significantly reduces imaging time, customizes magnetic field distribution, decreases peripheral nerve stimulation, and optimizes power consumption compared to conventional systems, enabling efficient imaging of multiple slices with lower power dissipation and improved gradient strengths.
Implementation Method 1
an array of gradient coils and a controller configured to generate several different field combinations in the array by applying different weightings to the magnitude of a current applied to each gradient coil
Implementation Method 2
The third type of magnetic field generated by the MRI system is termed a radio frequency (RF) field. The MRI system utilizes the RF field to excite spins within the object being imaged
Implementation Method 3
generate a spatially-varying magnetic field within said enclosure such that for at least first and second volumetric slices, a magnetic field magnitude associated with at least one location in the first volumetric slice is substantially equal to a magnetic field magnitude associated with a respective location in the second volumetric slice
Data Source
AI summary
A system for multi-slice magnetic resonance imaging (MRI) comprises a gradient coil array comprising a plurality of independent coils distributed about an enclosure; and a controller configured to concurrently actuate said plurality of coils so as to generate a spatially-varying magnetic field within said enclosure such that for at least first and second volumetric slices, a magnetic field magnitude associated with at least one location in the first volumetric slice is substantially equal to a magnetic field magnitude associated with a respective location in the second volumetric slice.