MRI Pulse Sequence With Periodic Gradients for Higher Resolution
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Solution Overview
Problem
Existing MRI methods for achieving high-resolution images often require intense radiofrequency pulses and strong magnetic field gradients, leading to increased hardware demands, low signal-to-noise ratio efficiency, and tissue heating.
Innovation Solution
A method and device that utilize a sequence of radiofrequency electromagnetic pulses and magnetic field gradients, including first gradients for localization and a second gradient with a non-zero time integral, generating periodic signal modulation to produce images with spatial frequencies above the Nyquist frequency, allowing for higher spatial resolution through image data combination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If intense radiofrequency pulses and strong magnetic field gradients are used to achieve high-resolution images, then spatial resolution is improved, but hardware performance requirements increase and tissue heating increases
Solution Approach 1:
The patent applies periodic magnetic field gradients with non-zero time integrals between successive radiofrequency pulses. This periodic action creates time-varying magnetisation patterns that encode high spatial frequency information, enabling super-resolution without requiring continuously intense gradients or high-power RF pulses, thereby reducing tissue heating while maintaining high spatial resolution
Solution Approach 2:
The patent changes the temporal parameters of the magnetic field gradients by introducing gradients with non-zero time integrals between pulses, rather than using only fully rewound gradients. This parameter change allows the system to encode additional spatial information through the time-varying nature of the gradients, achieving higher resolution without proportionally increasing gradient strength or RF pulse intensity
2Measurement precision
If intense radiofrequency pulses and strong magnetic field gradients are used to achieve high-resolution images, then spatial resolution is improved, but signal-to-noise ratio efficiency decreases
Solution Approach 1:
The periodic application of magnetic field gradients with non-zero time integrals creates coherent magnetisation patterns that constructive interfere to enhance the desired signal. This periodic encoding scheme improves SNR efficiency by systematically distributing the encoding information across multiple time points, allowing signal accumulation without proportionally increasing the energy input from RF pulses or gradients
Solution Approach 2:
The patent maintains continuous useful action by applying a sequence of radiofrequency pulses with interspersed magnetic field gradients throughout the imaging period. This continuous encoding process efficiently utilizes the available signal evolution time, extracting maximum information from the magnetisation dynamics without wasted time periods, thereby improving SNR efficiency while achieving high resolution
3Measurement precision
If intense radiofrequency pulses and strong magnetic field gradients are used to achieve high-resolution images, then spatial resolution is improved, but hardware performance requirements increase
Solution Approach 1:
The patent modifies the temporal parameters of existing gradient systems by introducing gradients with non-zero time integrals between pulses, rather than requiring entirely new hardware capabilities. This parameter-based approach allows standard MRI hardware to achieve super-resolution by changing how gradients are timed and shaped, avoiding the need for higher-performance gradient amplifiers or faster-switching hardware
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 approach enables the generation of high-resolution MRI images with reduced hardware requirements and minimized tissue heating by leveraging periodic spatial variations in magnetization to enhance image resolution beyond conventional limits.
Implementation Method 1
During an MRI scan the subject to be scanned is placed in a static magnetic field, and the magnetic field causes nuclei within the subject to become magnetised with a net magnetisation aligned in parallel with the magnetic field
Implementation Method 2
The subject is then exposed to an electromagnetic pulse, typically a radiofrequency pulse, generated by a transmitter. The frequency and duration of the pulse is chosen to perturb the net magnetisation vector of the protons, in particular to tilt the net magnetisation vector perpendicularly to the static magnetic field
Implementation Method 3
As the protons return to a lower energy state by relaxation, their precession creates a magnetic flux which can be detected by a receiver
Implementation Method 4
Typically additional magnetic fields are applied to provide gradients within the overall magnetic field. These cause protons at different locations within the field to precess at different rates, so that a particular volume or slice of the subject can be selected and imaged
Data Source
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AI summary
A method for generating a magnetic resonance imaging, MRI, image of a subject, the method comprising: applying a magnetic field B0 to the subject; applying a sequence of electromagnetic pulses to the subject; applying further magnetic field gradients in addition to the magnetic field B0, the magnetic field gradients comprising a plurality of first gradients and at least one second gradient; measuring signal echoes produced by the object in response to a plurality of the electromagnetic pulses and the first and second magnetic field gradients; acquiring image data at a first spatial resolution from the signal echo produced by the object in response to the electromagnetic pulses and the first and second magnetic field gradients; and combining the image data acquired from signal echoes in order to produce at least one image of the object at a second spatial resolution, the second spatial resolution being higher than the first spatial resolution. The first gradients are fully rewound in the interval between successive electromagnetic pulses, while the at least one second gradient has a non-zero gradient- time integral between successive electromagnetic pulses. The phase of at least one electromagnetic pulse in the sequence of electromagnetic pulses is different to another electromagnetic pulse in the sequence of electromagnetic pulses.