Time-encoded ASL MRI sub-bolus length adjustment for ATD artifact reduction
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Solution Overview
Problem
Existing ASL techniques for determining blood perfusion in tissues suffer from arterial transit delay (ATD) artifacts due to inconsistent post-labeling delays, which are not patient-specific, leading to image quality issues in cases of abnormal tissue variations.
Innovation Solution
An imaging system that adjusts the sub-bolus length based on subject-specific parameters determined during the image acquisition process, using a combination of sub-bolus length determination and adaptive timing to minimize ATD artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a fixed post-labeling delay is used in ASL imaging, then the imaging protocol is simple and fast, but arterial transit delay artifacts occur in patients with abnormal tissue variations
Solution Approach 1:
The patent applies dynamics by making the sub-bolus length adjustable rather than fixed. The system dynamically adapts the sub-bolus length based on measured arterial transit time, allowing the imaging parameters to change in response to patient-specific conditions while maintaining efficient Hadamard encoding.
Solution Approach 2:
The patent changes the parameter of sub-bolus length based on measured arterial transit time. By adjusting this parameter according to patient-specific physiology, the system eliminates ATD artifacts while preserving the efficiency of the Hadamard encoding approach.
2Reliability
If the post-labeling delay is extended to accommodate delayed blood flow, then ATD artifacts are reduced, but the imaging time increases
Solution Approach 1:
The patent performs preliminary measurement of arterial transit time using initial images, then uses this information to optimize subsequent sub-bolus lengths. This preliminary action allows the system to avoid unnecessary delays while ensuring accurate perfusion measurements.
Solution Approach 2:
The system uses feedback from measured arterial transit time to adjust sub-bolus lengths. By continuously monitoring and adjusting parameters based on measured physiological conditions, the system optimizes imaging time while maintaining measurement accuracy.
3Reliability
If individualized post-labeling delays are determined for each patient, then image quality improves, but the complexity of the imaging protocol increases
Solution Approach 1:
The patent uses periodic Hadamard-encoded labeling cycles with different sub-bolus lengths to efficiently measure arterial transit time and perfusion. This periodic approach allows individualized parameter optimization without requiring complex non-periodic sequences.
Solution Approach 2:
The system uses a universal Hadamard encoding framework that can accommodate different sub-bolus lengths for different patients. This multi-functional approach allows the same basic protocol structure to be adapted to individual patient needs without requiring entirely different imaging sequences.
4Measurement precision
If multiple images are acquired with different timing parameters to determine optimal sub-bolus length, then measurement precision improves, but productivity decreases
Solution Approach 1:
The patent segments the imaging process into distinct phases: initial arterial transit time measurement using multiple images, followed by optimized perfusion imaging using the determined sub-bolus length. This segmentation allows precise measurement without compromising overall imaging efficiency.
Solution Approach 2:
The system performs a limited number of initial measurements with different timing parameters just enough to determine arterial transit time, then uses this information for the main perfusion imaging. This partial action approach provides sufficient precision without excessive imaging time.
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
Improves image quality by reducing ATD artifacts and ensuring accurate perfusion measurements by adapting the sub-bolus length and timing to individual patient anatomy and physiology.
Implementation Method 1
an MR signal from the tissue of interest, i.e. an MR signal from the labeled blood within the tissue of interest
Data Source
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AI summary
The invention relates to an imaging system (100) for generating a series of images of a subject. In the context of time-encoded ASL MRI, fluid boli are generated at a first location of the subject, wherein each fluid bolus comprises a sequence of sub-boli and wherein images of the series of images are acquired at a second location of the subject, after the fluid boli have been flowed to the second location. A sub-bolus length is determined based on at least one image of the already acquired images of the series of images, wherein a further fluid bolus comprising a sequence of sub-boli is generated at the first location, wherein at least one of the sub-boli has the determined sub-bolus length, and wherein a further image of the series of images is acquired at the second location of the subject, after the further fluid bolus has been flowed from the first location to the second location.