Variable Interval Pulse Train for MRI Component Discrimination
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Solution Overview
Problem
Conventional MRI methods using spin echo techniques struggle to obtain clear images of samples like the kidney, as the signal intensities of its components (kidney tissue, ureter, and blood) are similar, making it difficult to discriminate between them.
Innovation Solution
A nuclear magnetic resonance apparatus that applies a specific pulse train with adjustable π pulse intervals, allowing for distinct discrimination of components by varying the interval of π pulses, enabling clear contrast between different tissue types through the analysis of spin echo intensities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional spin echo method with fixed pulse intervals is used, then the imaging process is simple and fast, but the signal intensities of different components (kidney tissue, ureter, blood) become similar and cannot be discriminated
Solution Approach 1:
The pulse interval is changed from a fixed value to a variable parameter that can be dynamically adjusted. The system applies multiple π pulses at different time intervals (τ1, τ2, τ3, etc.) after the initial π/2 pulse, allowing the pulse sequence to adapt to different tissue types and their respective T2 relaxation characteristics, thereby achieving better component discrimination.
Solution Approach 2:
The key parameter changed is the pulse interval (time between π pulses). By varying this temporal parameter across multiple echoes, the system exploits differences in T2 relaxation times among different tissues (kidney tissue, ureter, blood) to create distinct signal intensity patterns that enable component discrimination.
2Measurement precision
If multiple π pulses are applied at different intervals to achieve component discrimination, then clear contrast between tissues is obtained, but the measurement time and sequence complexity increase
Solution Approach 1:
Instead of performing separate measurements for different pulse intervals, the system continuously acquires multiple echoes in a single continuous pulse sequence. The π pulses are applied sequentially at different intervals without interrupting the measurement, allowing all necessary data to be collected in one continuous operation rather than multiple separate scans.
Solution Approach 2:
The system performs preliminary determination of optimal pulse intervals based on expected tissue types or preliminary measurements, then uses these predetermined intervals for the main measurement. This allows the measurement protocol to be optimized in advance, reducing the need for extensive trial-and-error measurements during the actual imaging process.
Data Source
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AI summary
A nuclear magnetic resonance apparatus (100) includes: a static magnetic field former (10) that forms a static magnetic field; an object holder (2) that holds an object in the static magnetic field; a pulse applicator (51a) that applies a π/2 pulse having the Larmor frequency of an atom to be measured to the object in the static magnetic field, and then applies a π pulse having the Larmor frequency to the object at least a predetermined number of times (the predetermined number being two or more) at an interval of the predetermined period, the π pulse being applied for a first time at a time point at which half the predetermined period has elapsed after applying the π/2 pulse; and a detector (40) that detects the signal intensity of a spin echo signal generated from the object as a result of the last instance of the predetermined number of times of application of the π pulse.