MRI Signal Suppression Sequences for High SNR Imaging
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Solution Overview
Problem
Current whole-body MRI screening methods for metastatic tumors face challenges with low signal-to-noise ratio (SNR) and image distortion, particularly in large fields-of-view, which increases scan time and artifacts, and can be confused by bright signals from fluids and blood.
Innovation Solution
The implementation of a system and method that applies a fluid suppression technique followed by fat and flow suppression techniques using inversion recovery pulses and motion-sensitizing driven equilibrium sequences before the imaging pulse-gradient sequence, allowing for rapid acquisition of MR images with high SNR and minimal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple signal averages are obtained to improve image quality, then signal-to-noise ratio increases, but total scan time increases
Solution Approach 1:
The patent applies fluid suppression, fat suppression, and flow suppression preparation sequences before the imaging pulse-gradient sequence to pre-suppress unwanted signals. This preliminary action reduces background signals that would otherwise require multiple signal averages to overcome, thereby improving SNR while maintaining shorter scan times
2Measurement precision
If DW-EPI sequence is used to suppress background signals, then tumor detection improves, but image distortion increases in large fields-of-view
Solution Approach 1:
The patent segments the suppression process into three distinct preparation sequences: fluid suppression, fat suppression, and flow suppression. Each sequence targets specific background signals separately, achieving comprehensive background suppression without the severe distortion problems of DW-EPI in large fields-of-view
3Measurement precision
If STIR sequence is used for fat suppression, then tumor visibility improves, but bright signals from fluid and blood create confusion
Solution Approach 1:
The patent separates fat suppression from fluid and blood signal suppression by using distinct preparation sequences. Fat suppression is achieved through one sequence while fluid and blood suppression are handled by another, allowing tumor visibility to be improved without the confounding bright signals that occur with STIR sequence
Solution Approach 2:
The patent applies different suppression characteristics to different tissue types: fat suppression targets specific frequency ranges, while flow suppression targets moving tissues. This localized approach to signal suppression improves tumor conspicuity by selectively removing only the interfering signals while preserving lesion information
4Productivity
If rapid acquisition is implemented to reduce scan time, then productivity increases, but signal-to-noise ratio decreases
Solution Approach 1:
The patent implements multiple suppression preparation sequences before the imaging sequence to pre-remove unwanted signals. This preliminary action reduces background noise and interference, allowing rapid acquisition with maintained or improved signal-to-noise ratio by eliminating the need for multiple signal averages
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 enhances tumor conspicuity by suppressing background signals from fluids, fat, and moving tissues, resulting in high-quality images with reduced distortion and acquisition time, improving the detection of metastatic tumors and other lesions.
Implementation Method 1
When a substance such as human tissue is subjected to a uniform magnetic field (polarizing field B0), the individual magnetic moments of the spins in the tissue attempt to align with this polarizing field, but precess about it in random order at their characteristic Larmor frequency
Implementation Method 2
STIR is a fat suppression technique that exploits the increased transverse relaxation time (T2) of metastatic tumors to aid in distinguishing the tumor(s) from the background signal
Implementation Method 3
a flow suppression preparation sequence after the fat suppression technique and prior to the imaging pulse-gradient sequence, wherein the flow suppression preparation sequence is configured to suppress moving tissue signals
Data Source
AI summary
An MRI apparatus is disclosed, the MRI apparatus comprising a computer programmed to apply a fluid suppression technique prior to an imaging pulse-gradient sequence, wherein the fluid suppression technique is configured to suppress signals from fluids having long longitudinal relaxation times, and apply a fat suppression technique after the fluid suppression technique and prior to the imaging pulse-gradient sequence, wherein the fat suppression technique is configured to suppress fat signals. The computer is further programmed to apply a flow suppression preparation sequence after the fat suppression technique and prior to the imaging pulse-gradient sequence, wherein the flow suppression preparation sequence is configured to suppress moving tissue signals. The computer is also programmed to apply the imaging pulse-gradient sequence, cause the RF transceiver system to acquire MR signals during the imaging pulse-gradient sequence, and reconstruct an image from the acquired MR signals.