MR-ARFI Autofocusing via Phase-Sensitive Echo Separation
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Solution Overview
Problem
Current high-intensity focused ultrasound (HIFU) autofocusing methods using MR-ARFI imaging are time-consuming and require a large number of image acquisitions, leading to potential tissue damage and impracticality for clinical use, especially when treating tissues with aberrations like the skull.
Innovation Solution
The implementation of a magnetic resonance (MR) imaging system employing a fast spin echo (FSE) pulse sequence with phase-sensitive echo separation and combination techniques to reduce the number of image acquisitions needed for autofocusing, allowing for real-time, clinically feasible HIFU focusing by analyzing voxels at the target and surrounding tissue to determine aberrations and apply corrective phase/amplitude adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MR-ARFI autofocusing methods are used to achieve precise HIFU focusing through aberrating tissues, then focusing precision is improved, but the number of image acquisitions increases significantly, making the procedure time-consuming and potentially damaging to healthy tissue
Solution Approach 1:
The patent segments the large number of required image acquisitions into a smaller subset by using phase-sensitive echo separation techniques. Instead of acquiring multiple images at each focal point, the system separates phase information from magnitude information, allowing accurate focus determination with fewer acquisitions. This segmentation of information processing reduces the total number of image acquisitions needed while maintaining focusing precision.
Solution Approach 2:
The patent applies partial action by using only the necessary phase and magnitude information from MR-ARFI images for focus determination, rather than processing complete image datasets. By extracting only the essential phase-sensitive information needed for focusing correction, the system achieves accurate autofocusing with reduced image acquisitions, avoiding the time penalty of processing excessive data.
2Measurement precision
If conventional MR-ARFI autofocusing methods are used to correct aberrations, then focusing quality is improved, but the number of pre-therapeutic sonications increases, potentially damaging healthy tissue
Solution Approach 1:
The patent segments the information extraction process to obtain focus quality metrics from fewer image acquisitions. By using phase-sensitive echo separation, the system determines focusing quality with minimal sonications rather than requiring multiple measurements, thereby reducing exposure of healthy tissue to pre-therapeutic ultrasound energy.
Solution Approach 2:
The patent replaces the mechanical trial-and-error approach of conventional autofocusing (which requires multiple sonications and iterative adjustments) with a phase-sensitive information extraction method. This substitution allows the system to determine optimal focus settings with minimal mechanical intervention, reducing tissue damage from excessive sonications.
3Productivity
If the number of image acquisitions is reduced for faster autofocusing, then procedure time is reduced, but measurement precision and ability to correct aberrations may deteriorate
Solution Approach 1:
The patent replaces conventional magnitude-based image analysis with phase-sensitive MR-ARFI echo separation techniques. This substitution enables accurate aberration measurement and correction with fewer image acquisitions, as phase information provides more direct and sensitive feedback on focus quality than traditional magnitude-based methods. The system achieves both speed and precision by using this alternative measurement approach.
Solution Approach 2:
The patent changes the measurement parameter from magnitude-based image intensity to phase-sensitive echo information. By utilizing phase information which is more sensitive to small changes in focus position and aberration, the system achieves high measurement precision with reduced number of acquisitions, thereby improving autofocusing speed without sacrificing accuracy.
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 significantly reduces the number of image acquisitions required for autofocusing, enabling faster and more precise HIFU focusing through aberrating tissues, such as the skull, and minimizing pre-therapeutic sonications, making MR-ARFI-based autofocusing clinically feasible and possible in near-real time.
Implementation Method 1
an RF coil assembly configured to emit RF pulse sequences and arranged to receive resulting MR signals from a subject of interest
Implementation Method 2
a plurality of gradient coils positioned about a bore of a magnet
Implementation Method 3
a fast spin echo (FSE) pulse sequence comprising a preparation segment and a plurality of refocusing segments
Implementation Method 4
a first echo generated by magnetization pathways having an even number of phase inversions and a second echo generated by magnetization pathways having an even number of phase inversions
Data Source
AI summary
A system and method for MR imaging is disclosed. The method causes an RF coil assembly and plurality of gradient coils to apply a fast spin echo (FSE) pulse sequence comprising a preparation segment and a plurality of refocusing segments. The FSE pulse sequence generates a pair of echoes is generated in each of the plurality of refocusing segments that comprises a first echo generated by magnetization pathways having an even number of phase inversions and a second echo generated by magnetization pathways having an even number of phase inversions. MR signals are acquired from the first echo and the second echo and an image of at least a portion of a subject of interest is reconstructed from the acquired MR signals.