In-Phase Zero Echo Time MRI Demodulation Frequency
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
ZTE MRI is sensitive to chemical shift artifacts, particularly at fat-water tissue interfaces, which can lead to reduced signal and blurring in images due to the chemical shift difference between fat and water, complicating the differentiation of bone and soft tissues.
Innovation Solution
Adjusting the demodulation frequency of MR signals to a value between the Larmor frequencies of water and fat, allowing for improved in-phase imaging by setting the center frequency of the RF transceiver during pre-scan or post-processing, thereby reducing chemical shift artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high bandwidth is used to reduce chemical shift artifacts, then chemical shift artifacts are reduced, but signal-to-noise ratio decreases and flip angle is limited
Solution Approach 1:
The patent changes the demodulation frequency parameter from the conventional water Larmor frequency to a frequency between the water and fat Larmor frequencies. This parameter change allows the system to reduce chemical shift artifacts without requiring high bandwidth, thereby maintaining signal-to-noise ratio and flip angle capabilities.
2Measurement precision
If conventional water-frequency demodulation is used, then water signal is accurately detected, but chemical shift artifacts appear at fat-water interfaces
Solution Approach 1:
The patent introduces an intermediary demodulation frequency that lies between the water and fat Larmor frequencies. This intermediary frequency acts as a mediator that reduces the relative chemical shift difference for both water and fat signals, thereby minimizing chemical shift artifacts at fat-water interfaces while still allowing accurate detection of tissue signals.
3Productivity
If standard ZTE imaging is performed, then fast 3D imaging of ultrashort T2 tissues is achieved, but bone depiction is affected by soft tissue appearance variability
Solution Approach 1:
The patent modifies the demodulation frequency parameter in standard ZTE imaging to achieve uniform soft tissue appearance. This parameter change eliminates chemical shift artifacts that cause soft tissue appearance variability, thereby improving bone depiction quality while maintaining the fast imaging capability of ZTE.
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 exceptional soft-tissue uniformity and reduced out-of-phase signal artifacts, enhancing image quality for applications like bone and lung imaging, while maintaining or improving the signal-to-noise ratio.
Implementation Method 1
a short hard-pulse radio frequency (RF) excitation is used to produce a small flip angle
Implementation Method 2
obtain Larmor frequencies of water and/or fat for a region of interest of a subject to be imaged
Implementation Method 3
spatial encoding and data acquisition are started as the MR signal is created and completed shortly thereafter
Implementation Method 4
demodulating the received MR signals with the center frequency
Implementation Method 5
Hydrogen atoms in fat have a lower Larmor frequency than those in water because each hydrogen atom in fat molecules is surrounded by many other atoms (e.g., carbon atoms) which effects the magnetic field. This difference in Larmor frequency is known as the chemical shift.
Data Source
AI summary
Systems and methods for ZTE MRI are disclosed. An exemplary method includes obtaining Larmor frequencies of water and/or fat for a region of interest of a subject to be imaged at a pre-scan and setting a center frequency for an RF transceiver of the MR system at a value between the Larmor frequencies of water and fat. A ZTE pulse sequence is applied to the subject and MR signals in response to the ZTE pulse sequence are received from the subject. The received MR signals are demodulated with the center frequency and an in-phase ZTE image is generated from the demodulated MR signals.