CEST MRI Apparatus Frequency Band Segmentation for Peak Detection
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Solution Overview
Problem
Traditional CEST imaging techniques require longer imaging times due to the acquisition of multiple CEST images and complex computations for noise reduction, which can be less accurate and time-consuming, especially when detecting chemical-shift peaks in Z-spectra.
Innovation Solution
A magnetic resonance imaging apparatus and method that acquire and process magnetic resonance signal groups before and after contrast enhancement, calculating differences in Z-spectra to detect peaks related to chemical shifts, using a frequency band determined by the presence of contrast agents with different chemical shifts, and applying function fitting or signal-value distribution estimation to improve accuracy and reduce imaging time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional CEST imaging acquires multiple CEST images (201 images) and performs complex fitting computations to detect chemical-shift peaks, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The patent segments the frequency spectrum into multiple frequency bands, with each band centered on a specific chemical shift of interest. Instead of acquiring a complete Z-spectrum across the entire frequency range, the system acquires separate CEST images for each frequency band. This segmentation reduces the total number of images required while maintaining peak detection accuracy for each specific substance, thereby reducing imaging time.
Solution Approach 2:
The patent performs preliminary determination of the frequency band based on expected chemical shift values of contrast agents before acquiring CEST images. By pre-defining the frequency ranges of interest based on known chemical shift characteristics, the system avoids unnecessary acquisitions outside these bands and performs targeted fitting computations only within the predetermined frequency ranges, reducing both acquisition and processing time.
2Measurement precision
If traditional CEST imaging performs fitting by five approximations to detect multiple peaks in Z-spectrum, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts and isolates the frequency bands corresponding to specific contrast agents from the complete Z-spectrum. By focusing fitting computations only on these extracted frequency bands rather than the entire spectrum, the system reduces the number of approximations needed. Each frequency band can be fitted with fewer approximation functions, simplifying the computational process while maintaining accuracy for the target substances.
Solution Approach 2:
The patent divides the complex task of detecting multiple peaks across the entire Z-spectrum into separate, simpler tasks for each frequency band. Each band is processed independently with its own fitting computation, which requires fewer approximation functions than analyzing the complete spectrum. This segmentation reduces overall computational complexity while preserving the ability to detect multiple contrast agents.
3Measurement precision
If traditional CEST imaging acquires a complete Z-spectrum to reduce noise, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands and acquires CEST images for each band separately. By concentrating acquisition resources on specific frequency bands of interest rather than uniformly sampling the entire spectrum, the system achieves adequate signal-to-noise ratios for target substances with fewer total images, reducing imaging time while maintaining measurement precision for the contrast agents of interest.
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 reduces the length of imaging time, simplifies computations, and enhances the accuracy of peak detection, allowing for more precise determination of state quantities like temperature or pH in the imaging region.
Implementation Method 1
transmission of a radiofrequency (RF) saturation pulse at a frequency particular to the solute protons causes a phenomenon that saturation is transferred from the solute protons to the water protons, which are supposed to be unsaturated. Such a phenomenon is referred to as chemical exchange saturation transfer (CEST).
Implementation Method 2
the resonance frequency of the protons vary depending on their state, which is referred to as chemical shift
Data Source
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AI summary
An MRI apparatus (100) according to one embodiment includes an obtaining unit (136) obtains information about a contrast agent containing substances with mutually different chemical shifts; a determiner unit (138) determines, based on the information, a frequency band related to a decrease in a MR signal due to the chemical shifts; an acquirer unit (121) acquires, prior to contrast enhancement using the contrast agent, a first MR signal group in the frequency band by CEST imaging under different saturation pulse conditions; and acquire, after the contrast enhancement using the contrast agent, a second MR signal group in the frequency band by CEST imaging under different saturation pulse conditions; a calculator unit (140) calculates a difference between a first Z-spectrum generated based on the first MR signal group and a second Z-spectrum generated based on the second MR signal group; and a detector unit (142) detects, from the difference, peaks indicating the decrease in the MR signal due to the chemical shifts of the substances