PCASL Off-Resonance Correction via Optimized Encoding Scheme
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Solution Overview
Problem
Current methods for correcting off-resonance effects in pseudo-continuous arterial spin labeling (PCASL) and vessel-encoded PCASL (VEPCASL) are limited in their ability to address magnetic field inhomogeneities, leading to reduced labeling efficiency and signal-to-noise ratio (SNR) in perfusion images and errors in blood flow rate estimates, often requiring additional scans and manual intervention.
Innovation Solution
The implementation of an optimized encoding scheme (OES) that incorporates off-resonance correction into the pulse labeling train, using phase information from a field map to automate the choice of SNR-efficient encodings for any number and arrangement of vessels, thereby mitigating phase offsets and maintaining SNR without increasing scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional off-resonance correction methods are applied, then labeling efficiency is improved, but scan time increases and SNR is reduced
Solution Approach 1:
The patent applies preliminary action by performing off-resonance correction during the pulse labeling train itself rather than requiring separate correction scans. The correction is embedded in the labeling process, allowing phase offset compensation to occur concurrently with blood flow labeling, thus eliminating additional scan time while maintaining labeling efficiency.
Solution Approach 2:
The patent merges the off-resonance correction function with the arterial spin labeling process. By combining these two functions into a single integrated sequence, the system achieves both labeling and correction without requiring separate scans, thereby preventing SNR loss that would result from additional scanning.
2Reliability
If additional PCASL scans are performed for correction, then off-resonance effects are addressed, but total scan time increases and SNR is reduced
Solution Approach 1:
The patent maintains continuity of useful action by performing correction continuously during the normal labeling process rather than interrupting the scan for separate correction measurements. The phase offset compensation occurs continuously throughout the labeling train, ensuring reliable correction without breaking the continuous data acquisition that maintains SNR.
Solution Approach 2:
The system performs self-service correction by using the labeling data itself to calculate and apply phase offset corrections. The method extracts phase information from the labeling process and uses it to correct off-resonance effects within the same dataset, eliminating the need for separate correction scans that would reduce SNR.
3Measurement precision
If manual intervention is used for correction, then accurate phase offset calculation is achieved, but device complexity and operation difficulty increase
Solution Approach 1:
The patent implements feedback by automatically calculating phase offsets from the labeling data and using these calculations to adjust the encoding scheme. The system continuously monitors the labeling process, extracts phase information, and applies corrections based on this feedback loop, eliminating manual intervention while maintaining measurement precision.
Solution Approach 2:
The patent replaces manual calculation and adjustment procedures with automated computational methods. The system uses computer-based algorithms to calculate phase offsets and generate corrected encoding schemes, substituting manual operations with automated processing that maintains precision while improving ease of operation.
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 allows for accurate and efficient correction of off-resonance effects, maintaining high SNR and reducing errors in blood flow rate estimates, while being applicable to both PCASL and VEPCASL, and can be rapidly integrated into existing scanning protocols.
Implementation Method 1
off-resonance correction for pseudo-continuous arterial spin labeling... off-resonance in the labeling plane during PCASL... magnetic field inhomogeneity present in MRI, in particular present in the labeling plane
Data Source
AI summary
Systems and methods are provided to incorporate an off-resonance correction into the pulse labeling train of PCASL/VEPCASL. In one or more aspects, the systems and methods are based on a method for generating an encoding scheme for any number and arrangement of blood vessels. The off-resonance correction can be incorporated into the generation of optimized encodings to acquire arterial spin labeling (ASL) data, such as PCASL and VEPCASL data.