Portable MRI Using Rotating Magnet Array for Spatial Encoding
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Solution Overview
Problem
Conventional MRI systems are not portable due to the requirement for homogeneous static magnetic fields and high-power linear gradient fields, limiting their use to hospital settings and preventing rapid diagnostics in emergency situations such as hemorrhage detection.
Innovation Solution
A portable MRI system utilizing an inhomogeneous magnetic field generated by a rotating array of permanent magnets for spatial encoding, eliminating the need for gradient coils and enabling low-power, lightweight, and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI systems use homogeneous static magnetic fields and high-power linear gradient fields, then imaging precision and diagnostic accuracy are improved, but system weight, complexity, and power consumption increase significantly
Solution Approach 1:
The patent extracts and eliminates the gradient coil system from conventional MRI, using only a static magnetic field source. Spatial encoding is achieved through a single-frequency RF pulse with a quadratic phase term, removing the need for complex gradient fields while maintaining imaging capability
Solution Approach 2:
The patent changes the RF pulse parameters by incorporating a quadratic phase term (e.g., exp(j*k0*r^2)) into the excitation pulse. This parameter modification enables spatial encoding without requiring gradient fields, fundamentally altering how spatial information is encoded in the MRI signal
2Measurement precision
If conventional MRI systems use high-power gradient fields for spatial encoding, then spatial resolution is improved, but power consumption increases requiring high-power amplifiers
Solution Approach 1:
The patent removes the gradient coil system and associated high-power amplifiers, achieving spatial encoding through RF pulse design with quadratic phase modulation. This eliminates the need for high-power gradient field generation while preserving spatial resolution capability
Solution Approach 2:
The patent substitutes the mechanical/electrical gradient field generation system with a signal processing approach using RF pulses with quadratic phase terms. The spatial encoding function previously performed by gradient coils is replaced by mathematical modulation of the RF excitation signal
3Stability of the object's composition
If conventional MRI systems use homogeneous superconducting or permanent magnets, then magnetic field uniformity is improved, but system weight and fragility increase reducing portability
Solution Approach 1:
The patent extracts and removes the gradient coil system entirely, keeping only a static magnetic field source (which can be a simple permanent magnet). This reduction in system components significantly decreases weight and complexity while maintaining sufficient magnetic field characteristics for imaging
Solution Approach 2:
The patent changes the approach to magnetic field requirements by accepting and utilizing field inhomogeneities rather than requiring high uniformity. The quadratic phase RF pulse is specifically designed to work with inhomogeneous fields, converting what was previously a disadvantage into a functional feature
4Measurement precision
If conventional MRI systems require hundreds of amps of current for gradient fields, then spatial encoding capability is improved, but portability is reduced due to power requirements
Solution Approach 1:
The patent removes the gradient coil system and associated high-current power requirements. Spatial encoding is achieved through RF pulse design with quadratic phase terms, eliminating the need for hundreds of amps of current while maintaining spatial encoding capability
Solution Approach 2:
The patent substitutes the high-current gradient field system with a low-power RF signal processing approach. The spatial encoding function is transferred from the gradient coil hardware to the RF pulse waveform design, dramatically reducing power requirements and enabling portability
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 rapid and portable detection of hemorrhages and other brain injuries, accelerating treatment by allowing imaging at the site of injury or in critical care settings without the need for high-power amplifiers or cryogens, improving clinical outcomes.
Implementation Method 1
The permanent magnets generate a magnetic field that varies with spatial location in a plane transverse to the longitudinal axis of the magnet assembly
Implementation Method 2
The RF coil is configured to generate RF energy and receiving magnetic resonance signals from an object positioned in the magnet assembly
Data Source
AI summary
A portable magnetic resonance imaging (“MRI”) system that uses static magnetic field inhomogeneities in the main magnet for encoding the spatial location of nuclear spins is provided. Also provided is a spatial-encoding scheme for a low-field, low-power consumption, light-weight, and easily transportable MRI system. In general, the portable MRI system spatially encodes images using spatial inhomogeneities in the polarizing magnetic field rather than using gradient fields. Thus, an inhomogeneous static field is used to polarize, readout, and encode an image of the object. To provide spatial encoding, the magnet is rotated around the object to generate a number of differently encoded measurements. An image is then reconstructed by solving for the object most consistent with the data.