2D Spin Echo MRI with VERSE for Low-SAR Flow Compensation
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Solution Overview
Problem
Existing spin echo sequences used for multi-slice 2D MRI scans are very SAR intensive and do not effectively integrate flow compensation along slice, leading to undesirable artifacts and potential tissue heating.
Innovation Solution
Combining variable rate selective excitation (VERSE) with flow compensation along slice to tailor slice selection gradient waveforms, reducing RF power and minimizing motion-induced phase shifts, using configuration software to convert irregular VERSE gradients into modeled rectangular shapes for accurate calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional spin echo sequences are used for multi-slice 2D MRI scans, then flow compensation along slice can be applied to reduce flow artifacts, but the SAR becomes excessively high
Solution Approach 1:
The patent applies VERSE (Variable Rate Selective Excitation) to dynamically adjust the slice selection gradient waveform parameters. By varying the gradient amplitude and duration in a controlled manner, the technique achieves flow compensation along the slice direction while reducing the RF pulse power requirements, thereby lowering SAR without compromising flow artifact suppression
Solution Approach 2:
The invention introduces dynamic gradient waveforms that change over time during the RF pulse application. The slice selection gradient is modulated to follow the instantaneous frequency of the RF pulse, creating a time-varying gradient waveform that provides flow compensation. This dynamic approach allows flow compensation to be achieved with lower peak RF power compared to static gradient methods
2Use of energy by moving object
If VERSE is applied to reduce SAR, then RF power is reduced, but flow compensation along slice becomes ineffective
Solution Approach 1:
The patent merges the VERSE technique with flow compensation along slice by integrating the time-varying gradient waveform of VERSE with the flow compensation gradient moments. The slice selection gradient is designed to simultaneously achieve frequency modulation for selective excitation and provide the necessary gradient areas for flow compensation, combining both functions into a single optimized gradient waveform
3Manufacturing precision
If flow compensation along slice is implemented, then image quality improves, but the complexity of gradient waveform design increases
Solution Approach 1:
The patent employs preliminary design of the slice selection gradient waveform to predetermined target gradient moments that ensure flow compensation. By pre-calculating the required gradient areas and timing based on the desired flow compensation performance, the complex waveform design is simplified into a systematic process that achieves both flow compensation and VERSE objectives
Data Source
AI summary
Magnetic resonance imaging techniques integrating variable rate selective excitation (VERSE) and flow compensation along slice are described. According to an example, a method comprises determining, by a device comprising a processer, a two-dimensional (2D) spin echo sequence applicable for acquiring, via a MRI system, signal data associated with a slice of an anatomical region of a subject, wherein determining the 2D spin echo sequence comprises determining the 2D spin echo sequence in accordance with a combination of a VERSE protocol and a flow compensation along slice protocol. The method further comprises controlling, by the device, acquisition of the signal data by the MRI system using the 2D spin echo sequence, and reconstructing, by the device, an image of the slice from the signal data.