pCASL MRI Inversion Efficiency Evaluation
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Solution Overview
Problem
Current CASL techniques, including pCASL, are sensitive to local magnetic field inhomogeneities, leading to incomplete inversion of blood magnetization and inaccurate perfusion estimates, which complicates diagnostic interpretations and requires additional time-consuming measurements to assess labeling efficiency.
Innovation Solution
An MRI system and method that generates sequences of inverted and non-inverted blood boluses using specific RF pulse phases and gradients to evaluate magnetization inversion efficiency directly during the pCASL sequence, allowing for high temporal and spatial resolution without adding to scan time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CASL techniques including pCASL are used to measure perfusion, then non-invasive blood flow measurement is achieved, but sensitivity to local magnetic field inhomogeneities leads to incomplete inversion of blood magnetization and inaccurate perfusion estimates
Solution Approach 1:
The patent applies preliminary action by evaluating the inversion state of magnetization immediately after the labeling RF pulses are applied, before the blood flows into the imaging region. This allows the system to assess labeling efficiency in advance and use this information to correct or adjust subsequent perfusion measurements, thereby compensating for the sensitivity to magnetic field inhomogeneities that occurs during the labeling process
Solution Approach 2:
The patent implements feedback by using the evaluated inversion state information to adjust the perfusion estimation. The system measures the actual labeling efficiency through the inversion state evaluation and feeds this information back into the perfusion calculation process, allowing dynamic correction of perfusion estimates based on the actual labeling conditions achieved in each measurement
2Measurement precision
If additional measurements are performed to assess labeling efficiency, then measurement accuracy improves, but scan time increases
Solution Approach 1:
The patent merges the labeling efficiency assessment with the main perfusion measurement sequence by evaluating the inversion state of magnetization during the same scan. The system combines the labeling pulses with signal acquisition in a unified sequence, allowing simultaneous measurement of both perfusion and labeling efficiency without requiring separate additional measurement time
Solution Approach 2:
The patent applies multi-functionality by designing a measurement sequence that serves dual purposes: it performs the primary perfusion measurement while simultaneously evaluating the inversion state of magnetization to assess labeling efficiency. This single sequence accomplishes multiple measurement goals, eliminating the need for separate dedicated efficiency assessment scans
3Reliability
If flow-driven adiabatic inversion is used to label blood spins, then non-invasive perfusion measurement is enabled, but continuous RF power application creates large demand on MR system and limits stability
Solution Approach 1:
The patent applies periodic action by using pulsed RF labeling instead of continuous RF application. The system employs periodic labeling RF pulses applied at regular intervals (e.g., every 1 second) to achieve flow-driven adiabatic inversion, thereby reducing continuous RF power demand while maintaining the ability to label inflowing blood spins for non-invasive perfusion measurement
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 accurate and efficient estimation of labeling efficiency in individual vessels, improving the reliability and robustness of perfusion measurements by assessing inversion quality in real-time without increasing scan duration.
Implementation Method 1
generate a main magnetic field that orients the magnetization of blood within the subject
Implementation Method 2
first inversion RF pulses for inverting the magnetization in a first region
Implementation Method 3
predetermined sequences of inverted and non-inverted blood boli with inverted and non-inverted, respectively, magnetization are generated, which flow from the first region to the part to be imaged
Implementation Method 4
first inversion magnetic resonance signals are acquired, which are caused by the influence of the magnetization by the first inversion radio frequency pulses
Data Source
AI summary
An MRI system and method for generating MR images is provided. An MR signals acquisition unit is configured to generate a main magnetic field, orienting the magnetization of blood within a subject, and first inversion/non-inversion RF pulses such that predetermined sequences of blood boli with inverted/non-inverted magnetization are generated. First inversion/non-inversion MR signals can be acquired, which are caused by the influence on the magnetization by the first inversion/non-inversion RF pulses. MR images may be generated by an image generation unit based on imaging MR signals, acquired after the sequences of inverted and non-inverted blood boli have been flowed from the first region to the part to be imaged, and the predetermined sequences. An evaluation unit is configured to evaluate the inverting of the magnetization in the first region based on the first inversion and/or non-inversion MR signals. In one embodiment, the labeling efficiency of a pseudo continuous arterial spin labeling (pCASL) MRI experiment is performed.