MRI RF Pulse Combining for B1 Inhomogeneity Correction
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Solution Overview
Problem
Magnetic Resonance Imaging (MRI) apparatuses with magnetostatic field strengths exceeding 1.5 T face challenges in achieving homogeneous radio-frequency (RF) magnetic field strengths, leading to image degradations and inhomogeneities due to electrical losses and dielectric resonances, which conventional techniques have not fully addressed.
Innovation Solution
The MRI apparatus employs a dual data acquisition approach by executing pulse sequences based on two different RF pulse transmission conditions, with the combining unit selecting the maximum signal intensity between the two sets of data to reconstruct images, thereby improving image quality and reducing degradations caused by RF field inhomogeneities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetostatic field strength is increased to improve image resolution and contrast, then image quality is improved, but RF (B1) field inhomogeneity increases causing signal loss and contrast degradation
Solution Approach 1:
The patent divides the single high-field MRI acquisition into multiple separate acquisitions at different RF pulse transmission conditions (e.g., different flip angles or B1 field strengths). Each acquisition captures signal intensity data under specific conditions, and these segmented datasets are later combined through processing to produce the final image, thereby resolving the contradiction between high field strength benefits and inhomogeneity drawbacks
Solution Approach 2:
The patent systematically varies RF pulse transmission parameters (such as flip angle, B1 field strength, or pulse duration) across multiple acquisitions. By changing these parameters, the system obtains signal intensity measurements at different conditions, allowing subsequent combination to compensate for B1 inhomogeneities while maintaining the advantages of high magnetostatic field strength imaging
2Reliability
If conventional B1 homogenization techniques are applied to reduce RF (B1) inhomogeneity, then field homogeneity is improved, but image signal intensity and contrast are reduced
Solution Approach 1:
Instead of applying strong correction measures that overly suppress B1 inhomogeneity (which would reduce signal intensity), the patent uses multiple partial acquisitions at different RF conditions and combines them constructively. This partial action approach maintains sufficient signal intensity while adequately addressing field homogeneity issues through the combination process rather than aggressive single-acquisition correction
3Measurement precision
If multiple data acquisitions at different RF pulse transmission conditions are performed and combined, then image quality and signal uniformity are improved, but examination time is increased
Solution Approach 1:
The patent employs periodic or pulsed RF pulse transmissions at different conditions in a structured sequence, where each pulse acquisition is followed by signal processing and preparation for the next condition. This periodic action allows efficient use of examination time by systematically cycling through multiple RF conditions without unnecessary delays, balancing the trade-off between comprehensive data collection and examination duration
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 method effectively enhances image quality and contrast by ensuring more uniform signal intensities across the image, even in high-field MRI systems, by comparing and combining data from different RF pulse transmission conditions, thus mitigating the effects of RF field inhomogeneities.
Implementation Method 1
an MRI apparatus applies a radio-frequency pulse (hereinafter, an 'RF pulse') corresponding to a resonance frequency to a transmission coil, so that the transmission coil generates a radio-frequency magnetic field (hereinafter, an 'RF (B1) magnetic field')
Implementation Method 2
Imaging processes performed by Magnetic Resonance Imaging apparatus (hereinafter, 'MRI apparatus') use methods by which the inside of an examined subject is shown in an image while utilizing nuclear magnetic resonance phenomena
Implementation Method 3
the distribution of RF (B1) magnetic fields becomes inhomogeneous due to electrical losses and dielectric resonances occurring on the inside of the subject
Implementation Method 4
the distribution of RF (B1) magnetic fields becomes inhomogeneous due to electrical losses and dielectric resonances occurring on the inside of the subject
Data Source
AI summary
A magnetic resonance imaging apparatus according to an embodiment includes a first acquiring unit, a second acquiring unit, and a combining unit. The first acquiring unit is configured to acquire data by executing a pulse sequence based on a first radio-frequency pulse transmission condition. The second acquiring unit is configured to acquire data by executing a pulse sequence based on a second radio-frequency pulse transmission condition that is different from the first radio-frequency pulse transmission condition. The combining unit is configured to perform a combining process either on the data acquired by the first acquiring unit and the data acquired by the second acquiring unit or on data obtained by reconstructing the data acquired by the first acquiring unit and data obtained by reconstructing the data acquired by the second acquiring unit.