Hybrid Adiabatic-Rectangular Pulse Train for Uniform Cardiac Saturation
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) techniques face challenges in achieving uniform T1-weighting at 3 T due to higher B0 and B1+ variations, leading to non-uniform saturation of magnetization, especially in the heart, which affects the interpretation and analysis of first-pass cardiac perfusion MR images.
Innovation Solution
A hybrid adiabatic-rectangular pulse train is developed, combining non-selective rectangular RF pulses and an adiabatic half-passage pulse to achieve complete saturation of magnetization within the whole heart while maintaining clinically acceptable Specific Absorption Rate (SAR) limits, using a configuration of RF pulses that rotate longitudinal magnetization onto the transverse plane and minimize residual magnetization below a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-selective 90° pulse is used for saturation, then the pulse duration is short and device complexity is low, but uniform T1-weighting deteriorates due to B0 and B1+ inhomogeneities at 3T
Solution Approach 1:
The saturation pulse is divided into multiple rectangular RF pulses with different flip angles (e.g., 96°, 228°, 141°) applied in sequence. Each pulse contributes differently to the overall saturation effect, and their combined action achieves uniform magnetization saturation across regions with varying B0 and B1+ fields, resolving the contradiction between simplicity and uniformity.
Solution Approach 2:
The invention changes the parameters of the RF pulses by using different flip angles for each pulse in the train. This parameter variation allows the pulse train to compensate for B0 and B1+ inhomogeneities, achieving uniform T1-weighting without requiring complex adaptive systems.
2Reliability
If adiabatic B1-insensitive rotation (BIR-4) pulse is used, then uniform T1-weighting is improved, but specific absorption rate (SAR) increases significantly
Solution Approach 1:
The invention uses simple rectangular RF pulses that are computationally and energetically efficient, replacing the complex and energy-intensive adiabatic BIR-4 pulse. Although each individual rectangular pulse is simpler, the train of pulses achieves comparable uniformity at significantly lower SAR, making the solution more practical for clinical use.
3Reliability
If RF pulse train with longer duration is used, then saturation uniformity is improved, but pulse duration increases beyond optimal limits
Solution Approach 1:
The invention applies a train of RF pulses where the individual pulse durations and flip angles are optimized to achieve sufficient saturation uniformity without excessive total duration. By using multiple pulses with moderate parameters rather than a single long pulse, the system achieves good uniformity while keeping the total time within acceptable limits for clinical perfusion imaging.
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 hybrid pulse train effectively performs complete saturation of magnetization across the whole heart within clinically acceptable SAR limits, offering improved uniformity and accuracy in T1-weighting, comparable to BIR-4 pulses but with significantly reduced RF energy deposition, enabling multi-slice first-pass cardiac perfusion MRI.
Implementation Method 1
magnetic resonance imaging
Implementation Method 2
transmit radio-frequency (RF) field (B1+)
Implementation Method 3
nonselective adiabatic half-passage pulse
Data Source
AI summary
System, method and computer-accessible medium can be provided to facilitate a hybrid adiabatic-rectangular pulse train for saturation of magnetization within an anatomical structure. -Using such exemplary embodiments, it is possible to determine information by combining a first information associated with a first nonselective rectangular radio frequency (RF) pulse, a second information associated with a second nonselective rectangular RF pulse, and a third information associated with a nonselective adiabatic half-passage pulse. Further, it is possible to rotate the longitudinal magnetization onto a particular plane (e.g., the transverse plane) based on the information. In addition, it is possible to minimize and/or achieve the residual longitudinal magnetization to be less than a predetermined threshold value (e.g., 2% of equilibrium magnetization) within the anatomical structure using a configuration of RF pulses.