MRI Pulse Sequence With Alternating RF Pulses for Cardiac Imaging
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Solution Overview
Problem
Current MRI sequences for cardiac imaging face challenges in artifact sensitivity, motion sensitivity, and T2-sensitivity, which affect the quality of magnetic resonance image data acquisition.
Innovation Solution
An MRI pulse sequence is developed that includes a contrast preparation module with a train of radio-frequency pulses of equal flip angle magnitude but alternating signs, followed by an imaging module using a steady-state free precession scheme, allowing for adjustable T2/T1-weighted contrast and reduced susceptibility to artifacts, with options for varying flip angles and incorporating spoiler gradients to improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MRI sequences are used for cardiac imaging, then the imaging process is simple, but T2-sensitivity is insufficient and artifact sensitivity is high
Solution Approach 1:
The pulse sequence is divided into distinct functional modules: a contrast preparation module with a train of radio-frequency pulses, followed by an imaging module using steady-state free precession. This segmentation allows each module to be optimized independently - the preparation module enhances T2-sensitivity through specific pulse patterns while the imaging module captures the contrast efficiently, resolving the contradiction between simplicity and precision.
Solution Approach 2:
The contrast preparation module performs preliminary action by applying a train of radio-frequency pulses with alternating signs before the imaging acquisition. This pre-preparation of magnetization contrast enhances T2-sensitivity and reduces artifact sensitivity in the subsequent imaging phase, allowing for higher measurement precision without proportionally increasing overall sequence complexity.
2Measurement precision
If conventional MRI sequences are used, then the acquisition is fast, but motion sensitivity is high reducing image quality
Solution Approach 1:
The pulse sequence incorporates dynamic elements including a train of radio-frequency pulses with alternating signs that can be adjusted in duration and intensity, allowing adaptation to cardiac motion. The steady-state free precession imaging module also provides dynamic flexibility in acquisition timing, enabling the sequence to synchronize with cardiac cycles and reduce motion sensitivity while maintaining fast acquisition speeds.
3Measurement precision
If conventional MRI sequences are used, then the protocol is simple, but artifact sensitivity is high
Solution Approach 1:
The train of radio-frequency pulses with alternating signs converts potentially harmful effects into beneficial contrast enhancement. The alternating sign pattern creates a steady-state free precession effect that enhances T2-sensitivity and simultaneously reduces artifact sensitivity by suppressing unwanted signal contributions, effectively turning a complex pulse pattern into a beneficial imaging tool.
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
The proposed MRI pulse sequence enhances T2-sensitivity and reduces artifacts, providing better image quality for cardiac imaging, particularly useful in diagnosing acute infarcts and myocardial ischemia by allowing adjustable BOLD sensitivity and improved motion tolerance.
Implementation Method 1
MRI is based on the physical phenomenon of nuclear magnetic resonance
Implementation Method 2
The induced contrast is usually T2/T1-weighted. Therefore, a MR image reconstructed from the acquired magnetic resonance image data exhibits a T2/T1-weighted contrast.
Implementation Method 3
Radio-frequency energy, e.g. radio-frequency pulses, can excite these 'ordered' nuclear spins to a specific oscillation, i.e. a precession around the main magnetic field. This oscillation generates a signal that can be detected by appropriate reception coils.
Implementation Method 4
By the use of non-homogeneous magnetic fields generated by gradient coils, the signals can be spatially coded in all three spatial directions.
Implementation Method 5
In a further embodiment, the train of radio-frequency pulses is succeeded by a spoiler gradient. Such a spoiler gradient destroys the remaining transverse magnetization, improving the quality of the succeeding the image data acquisition.
Data Source
AI summary
In a magnetic resonance imaging (MRI) method, in the form of an MRI pulse sequence, and an apparatus for acquiring MRI data from an object, a contrast preparation module is applied to the object for preparing a contrast in the magnetization of nuclear spins of the object, and an imaging module is applied to the object after the contrast preparation module for acquisition of magnetic resonance image data reflecting the prepared contrast. The contrast preparation module includes a train of radio-frequency pulses with the same flip angle magnitude α, the respective signs of the flip angles alternating from radio-frequency pulse to radio-frequency pulse.