Arterial Spin Labeling with Variable TR and Interleaved PLD
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Solution Overview
Problem
Current arterial spin labeling (ASL) techniques for measuring transit delays and arterial blood flow are time-consuming and sensitive to motion, requiring multiple scans and assumptions that can lead to underestimation and errors in cerebral blood flow (CBF) estimation.
Innovation Solution
The implementation of variable repetition time (TR) and interleaved post-labeling delay (PLD) in ASL measurements reduces scan time and motion sensitivity, allowing for accurate estimation of transit delay and CBF without additional calibration scans, using a pre-saturation pulse to saturate the imaging slice before the labeling pulse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple separate ASL experiments are performed at several different post-labeling delays to measure transit delays and CBF, then measurement precision is improved, but scan time increases significantly
Solution Approach 1:
The patent combines multiple ASL experiments at different post-labeling delays into a single interleaved acquisition sequence. Multiple PLDs are performed in an interleaved manner within one scan, allowing simultaneous measurement of transit delay and CBF without requiring separate experiments for each parameter, thus reducing total scan time while maintaining measurement precision
Solution Approach 2:
The patent implements variable repetition time (TR) where TR is adjusted based on the specific post-labeling delay being measured. This dynamic TR adjustment optimizes the balance between signal quality and scan time for each PLD, allowing flexible and efficient acquisition of multiple transit delay points without fixed time constraints
2Measurement precision
If additional calibration scans are performed to map T1 and blood magnetization for CBF quantification, then measurement precision is improved, but scan time and motion sensitivity increase
Solution Approach 1:
The patent makes the ASL sequence multi-functional by simultaneously achieving several objectives within a single acquisition: measuring transit delay at multiple PLDs, estimating T1 values, and quantifying CBF. This eliminates the need for separate calibration scans for T1 and M0 mapping, reducing total scan time and minimizing motion sensitivity while maintaining CBF quantification accuracy
Solution Approach 2:
The ASL sequence performs self-calibration by using the same acquisition data to estimate T1 and blood magnetization parameters needed for CBF quantification. The sequence generates its own calibration information through the interleaved PLD measurements, eliminating the need for external calibration scans and reducing overall scan time
3Ease of operation
If fixed repetition time is used in ASL experiments, then protocol simplicity is maintained, but scan time cannot be optimized for different post-labeling delays
Solution Approach 1:
The patent introduces dynamic variable TR that adapts to the specific post-labeling delay being measured. Instead of using a fixed TR for all PLDs, the repetition time is adjusted for each PLD to optimize signal acquisition efficiency, reducing total scan time while maintaining protocol manageability through automated parameter adjustment
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 scan time by approximately 30% and decreases motion sensitivity, enabling accurate transit delay and CBF measurement with improved accuracy and reduced errors, particularly in white matter where T1 differences are significant.
Implementation Method 1
a pre-saturation pulse to saturate the imaging slice before the labeling pulse
Implementation Method 2
manipulating the magnetic spins in a body part and processing measured responses from the magnetic spins
Data Source
AI summary
Techniques and systems are disclosed for measuring arterial transit delay using pseudo- continuous arterial spin labeling (ASL) with variable TR and interleaved post-labeling delays. In one aspect, a magnetic resonance imaging method for measure arterial blood flow and transit delay using arterial spin labeling (ASL) includes applying an ASL pulse sequence. The ASL pulse sequence includes a pre- saturation pulse, and a labeling pulse. The method includes performing data acquisition to measure a transit delay, which represents a time needed for labeled blood to arrive in an imaging slice.