MRI K-space Acquisition Using Variable Gradient Strengths
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Solution Overview
Problem
Magnetic resonance imaging (MRI) techniques with ultrashort echo times face challenges in achieving optimal image quality and signal-to-noise ratio due to delays and noise exposure, particularly in scanning the center of the k-space, which is not fully acquired in sequences like UTE, zTE, WASPI, and PETRA, requiring interpolation or additional data acquisition.
Innovation Solution
The method involves acquiring measured data with different gradient field strengths for scanning the k-space, allowing for varying time intervals between acquisitions, which reduces noise and improves signal-to-noise ratio by using larger intervals for the k-space center and shorter intervals for the outer areas, enabling efficient radial scanning and frequency encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a minimum time is required to switch over between transmit and receive operation, then the center of the k-space cannot be acquired, but the switching time can be reduced
Solution Approach 1:
The patent segments the k-space acquisition into multiple passes with different gradient field strengths. The first pass with lower gradient strength acquires data from a first time interval, while the second pass with higher gradient strength acquires data from a second time interval. This segmentation allows the k-space center to be acquired without requiring extended switching time, as each pass contributes different portions of the k-space data.
Solution Approach 2:
The patent dynamically adjusts the gradient field strength between two different values (first gradient field strength and second gradient field strength) depending on the time interval and k-space region being acquired. This dynamic adjustment allows optimal data acquisition for both the k-space center and outer regions while maintaining efficient switching between transmit and receive operations.
2Speed
If gradient field strength is increased for faster scanning, then noise exposure increases, but scanning speed is improved
Solution Approach 1:
The patent applies different gradient field strengths to different regions of the k-space based on local requirements. The first gradient field strength (lower) is used for acquiring k-space center data where noise exposure should be minimized, while the second gradient field strength (higher) is used for acquiring outer k-space data where faster scanning is prioritized. This local differentiation resolves the contradiction between scanning speed and noise exposure.
3Object-affected harmful factors
If ultrashort echo time sequences are used, then noise exposure is reduced, but image quality and signal-to-noise ratio deteriorate
Solution Approach 1:
The patent creates a composite acquisition strategy that combines data from two different gradient field strengths. By merging the low-noise data from the first gradient field strength acquisition with the high-speed data from the second gradient field strength acquisition, the method produces a composite k-space dataset that achieves both low noise exposure and high signal-to-noise ratio in the final reconstructed image.
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 enhances image quality and signal-to-noise ratio by optimizing gradient field strengths and time intervals, reducing noise and enabling robust reproduction of response signals, particularly in the k-space center, while maintaining efficient scanning of the outer areas.
Implementation Method 1
a gradient device (4) for generating a gradient field in an acquisition volume (2)
Implementation Method 2
a radio frequency device (7) for irradiating a radio frequency pulse into the acquisition volume (2)
Data Source
AI summary
In a method for MRI where k-space describing spatial frequencies in an acquisition volume (AV) is scanned, a first measured data acquisition is performed in the AV with a first gradient field strength of a gradient field, including irradiating a RF pulse into the AV and acquiring a first series of measured values spaced apart temporally, a second measured data acquisition is performed with a second, different gradient field strength, including irradiating a RF pulse into the AV and acquiring a second series of measured values spaced apart temporally. With the first measured data acquisition, the first measured values for a respective response signal are acquired at a first time interval from one another and with the second measured data acquisition, the second measured values for a respective response signal are acquired at a second, different time interval from one another.