Ultra-short Echo Time ISIS Sequence for Liver Fat MRS
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Solution Overview
Problem
Current 1H-magnetic resonance spectroscopy (MRS) methods for determining liver fat content face challenges due to variability in T2 relaxation times, leading to errors in fat content determination, especially with long echo times and the need for breath-holding during measurements.
Innovation Solution
The ISIS sequence is employed with ultra-short echo times, using 180° pulses to select the volume of interest and acquire data in multiple cycles, allowing for automatic acquisition during free breathing and minimizing T2 effects, enabling high signal-to-noise ratio and smaller volume of interest measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long echo time is used in single-voxel spectroscopy, then the signal acquisition is improved, but the T2 relaxation variability causes significant errors in fat content determination
Solution Approach 1:
The patent inverts the conventional approach by using ultra-short echo times (TE < 10 ms) instead of long echo times. This inversion eliminates T2 relaxation effects that cause measurement errors, thereby improving fat content determination accuracy while avoiding the time loss associated with long echo times.
Solution Approach 2:
The patent changes the echo time parameter from conventional long durations to ultra-short durations (TE < 10 ms). This parameter change fundamentally alters the measurement regime, making T2 relaxation effects negligible and improving measurement precision without the trade-off of increased measurement time.
2Measurement precision
If multiple STEAM sequences with different echo times are repeated, then T2 correction can be calculated, but the acquisition time increases and signal-to-noise ratio decreases
Solution Approach 1:
The patent extracts and eliminates the need for T2 correction by using ultra-short echo times. Instead of performing multiple sequences to calculate T2 correction, the method directly acquires spectra at TE < 10 ms where T2 effects are negligible, thereby improving acquisition speed while maintaining measurement precision.
Solution Approach 2:
The patent skips the lengthy process of multiple STEAM sequence repetitions by rushing through with a single ultra-short echo time acquisition. This approach achieves the measurement goal in one shot, dramatically improving productivity without sacrificing accuracy.
3Measurement precision
If conventional MRS sequences are used, then the volume of interest can be selected, but breath-holding is required which lengthens measurement time and limits patient compliance
Solution Approach 1:
The patent uses partial action by acquiring spectra at ultra-short echo times before significant T2 decay occurs. This partial acquisition strategy eliminates the need for breath-holding, improving ease of operation and patient compliance while maintaining volume selection accuracy through the ISIS sequence.
4Loss of time
If ultra-short echo time is used in ISIS sequence, then T2 effects are minimized and measurement time is reduced, but the signal-to-noise ratio must be maintained
Solution Approach 1:
The patent merges multiple ISIS sequence acquisitions with different 180° pulse combinations to achieve signal averaging. This combining strategy maintains the signal-to-noise ratio despite using ultra-short echo times, while still reducing overall measurement time compared to conventional methods.
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 results in accurate, rapid, and reliable liver fat content determination with ultra-short echo times (<1 ms), independent of T2 effects and iron content, allowing for smaller VOIs and reducing measurement time, enabling fat content assessment without breath-holding.
Implementation Method 1
The invention concerns a method for generating magnetic resonance spectroscopy data from a volume of interest in the body of a person to be examined
Implementation Method 2
followed by a non-selective 90° pulse, after which a free induction decay (FID) is recorded
Implementation Method 3
after which a free induction decay (FID) is recorded
Data Source
AI summary
In a method and apparatus for generating magnetic resonance spectroscopy data from a VOI, in particular in the liver, image data are acquired from an examination area, which contains an organ affected by breathing, and the image data are evaluated until the position of the organ lies within a specific region. One or more of the eight acquisition cycles of an ISIS sequence are executed in order to acquire magnetic resonance spectroscopy data from the VOI, with repetitions until all eight acquisition cycles of the ISIS sequence have been executed. The magnetic resonance spectroscopy data acquired with the ISIS sequence are reconstructed to form a spectrum. The data acquisition has an ultra-short echo time.