MRI Navigator Echo Timing Control for Reduced TR Extension
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Solution Overview
Problem
Existing MRI technologies face challenges in minimizing the extension of repetition time (TR) due to navigator echo acquisition, which prolongs imaging time and burdens the operator or subject, especially in short TR imaging, while maintaining time resolution for body motion detection.
Innovation Solution
An MRI apparatus that automatically controls the timing of navigator echo acquisition based on the repetition time (TR) of the pulse sequence, acquiring navigator echoes at a predetermined frequency, either for each slice in long TR imaging or reducing the number of acquisitions in short TR imaging to maintain time resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If navigator echo acquisition is performed for each TR to maintain time resolution for body motion detection, then body motion detection capability is improved, but imaging time is prolonged due to TR extension
Solution Approach 1:
The patent applies dynamics by making the navigator echo acquisition strategy adaptive based on TR length. The system dynamically adjusts between two modes: acquiring navigator echoes for each TR when TR is short (to maintain time resolution), and acquiring navigator echoes for each slice when TR is long (to reduce unnecessary acquisitions). This dynamic adaptation resolves the contradiction by optimizing the balance between motion detection capability and imaging time based on the specific pulse sequence parameters being used.
2Reliability
If navigator echo is acquired separately from image signal, then body motion can be detected, but pulse sequence length is extended and imaging time is prolonged
Solution Approach 1:
The patent applies partial action by selectively acquiring navigator echoes only when necessary. Instead of acquiring navigator echoes for every TR or every slice unconditionally, the system performs partial acquisitions based on the TR length. When TR is long, the system reduces navigator echo acquisitions to only those necessary for adequate motion detection, rather than acquiring them for every slice. This partial action approach maintains sufficient body motion detection capability while avoiding excessive acquisitions that would unnecessarily prolong imaging time.
3Measurement precision
If navigator echo acquisition frequency is increased to improve time resolution, then body motion detection accuracy is improved, but TR extension increases
Solution Approach 1:
The patent applies parameter changes by adjusting the navigator echo acquisition frequency based on the TR parameter. The system monitors the TR length and changes the acquisition frequency parameter accordingly: using higher frequency (acquisitions per TR) when TR is short, and lower frequency (acquisitions per slice) when TR is long. This parameter-based adaptation resolves the contradiction by ensuring adequate time resolution for motion detection without causing excessive TR extension, as the acquisition frequency is optimized to match the pulse sequence characteristics.
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 effectively suppresses TR extension without reducing time resolution for body motion detection, saving time and effort by automating navigator echo timing control.
Implementation Method 1
nuclear magnetic resonance is induced within the examination target, nuclear magnetic resonance signals are collected
Implementation Method 2
a gradient magnetic field is applied to a position different from the original gradient magnetic field
Implementation Method 3
the motion of the subject is estimated from a change in data (hereinafter, referred to as navigator data) consisting of a series of navigator echoes obtained in time series
Data Source
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AI summary
Provided is a technique of minimizing an influence of extension of repetition time TR in magnetic resonance imaging due to a navigator echo for body motion detection without reducing a time resolution of body motion detection in imaging using the navigator echo. In a case in which imaging is performed in accordance with a predetermined pulse sequence by using an MRI apparatus, control of generating a navigator echo at a predetermined timing in the pulse sequence is performed, and control of making a timing at which the navigator echo is acquired different between a case in which a repetition time of the pulse sequence is equal to or greater than a preset threshold value and a case in which the repetition time is less than the threshold value is performed.