Multiple RF Coils for CEST MRI Parallel Imaging
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Solution Overview
Problem
CEST imaging is time-consuming and susceptible to motion artifacts due to limited RF pulse duty cycle and sensitivity to RF field inhomogeneities, especially in high-field MRI scanners.
Innovation Solution
The use of multiple RF coils for parallel transmission and reduced Field of View (FOV) imaging with interleaved RF pulses and k-space undersampling to increase RF pulse sequence duty cycle and reduce imaging time and artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a train of high-power RF saturation pulses is applied to achieve CEST effect, then CEST saturation efficiency is improved, but imaging time is excessively prolonged and motion artifacts increase
Solution Approach 1:
The patent divides the RF saturation task across multiple independent RF coils, each applying saturation pulses to different spatial regions or frequency bands simultaneously. This segmentation allows parallel acquisition of CEST data without requiring sequential scanning, thereby maintaining high saturation efficiency while reducing total imaging time
Solution Approach 2:
The patent introduces parallel transmission across multiple RF coils as an additional dimension for achieving CEST saturation. Instead of relying solely on temporal sequencing of saturation pulses in a single coil, the system exploits the spatial and channel dimension provided by multiple coils to achieve simultaneous saturation, effectively transforming a time-consuming sequential process into a parallel operation
2Measurement precision
If multiple images are acquired with saturation pulses at different resonance frequencies to analyze CEST effect, then measurement accuracy is improved, but acquisition time increases and motion artifacts worsen
Solution Approach 1:
The patent assigns different resonance frequency saturation tasks to different RF coils or coil elements, allowing simultaneous acquisition of multiple frequency-point CEST data. This segmentation of frequency sampling across parallel channels maintains measurement accuracy while reducing the temporal window vulnerable to motion artifacts
Solution Approach 2:
The patent implements continuous or near-continuous CEST data acquisition by having multiple RF coils simultaneously apply saturation pulses at different frequencies and acquire signals in parallel. This continuous parallel acquisition reduces gaps between measurements and minimizes the impact of patient motion during the scanning process
3Measurement precision
If RF pulse width and duty cycle are increased to enhance CEST effect, then saturation efficiency is improved, but hardware constraints and B1 inhomogeneity sensitivity worsen
Solution Approach 1:
The patent distributes the total RF saturation power across multiple RF coils, with each coil operating at lower power levels and lower individual B1 amplitudes. This segmentation of RF power delivery maintains overall CEST saturation efficiency while reducing each coil's sensitivity to B1 inhomogeneities and avoiding excessive specific absorption rate (SAR)
Solution Approach 2:
The patent changes the operational parameters of the RF system by using multiple coils with reduced individual duty cycles and lower B1 field amplitudes compared to a single high-power coil. This parameter transformation maintains the cumulative saturation effect while operating within hardware constraints and reducing sensitivity to RF field inhomogeneities
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 significantly reduces imaging time and motion artifacts while enhancing CEST saturation efficiency and sensitivity, making CEST imaging clinically viable without prolonged scan times.
Implementation Method 1
A chemical exchanged saturation transfer (CEST) method utilizes a train of high-power radiofrequency (RF) saturation pulses that are applied at the resonance frequency of exchangeable protons, after which saturation is transferred through chemical exchange to a bulk water pool leading to MR signal loss that yields contrast
Implementation Method 2
saturation is transferred through chemical exchange to a bulk water pool
Implementation Method 3
An MR imaging system uses multiple RF coils for reducing image acquisition time, suitable for chemical exchange saturation transfer (CEST) imaging
Data Source
AI summary
An MR imaging system uses multiple RF coils, for reducing image acquisition time, suitable for chemical exchange saturation transfer (CEST) imaging. Multiple RF (Radio Frequency) coils provide CEST imaging preparation in an anatomical volume by providing multiple interleaved RF pulses. The multiple interleaved RF pulses provide substantially increased RF pulse sequence duty cycle in the multiple RF coils relative to a duty cycle provided by a single coil of the multiple RF coils. The multiple RF coils subsequently provide RF excitation pulses in a reduced anatomical volume using k-space undersampling in an accelerated imaging method using the multiple RF coils and enable subsequent acquisition of associated RF echo data for deriving a CEST image.