MRI Calibration Data Determination via Central K-Space Acquisition
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Solution Overview
Problem
Current magnetic resonance imaging techniques face challenges in rapidly determining calibration data for image reconstruction, particularly in wave techniques, where deviations in gradient coils lead to artifacts due to imperfections like eddy currents, resulting in inadequate remediation of aliasing artifacts.
Innovation Solution
A method is introduced to efficiently determine calibration data by specifying acquisition shots that prioritize data acquisition in the central region of k-space, allowing for early determination of calibration data before completing all scan data acquisition, thereby enabling quicker image reconstruction and minimizing the impact of gradient deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all k-space data is acquired symmetrically according to Nyquist theorem, then image quality and resolution are maintained, but scan time is excessively long
Solution Approach 1:
The patent applies partial Fourier acquisition by sampling only a portion of k-space (e.g., 6/8 or 5/8 of total k-space lines) instead of complete symmetric sampling. This partial action reduces scan time while using reconstruction algorithms to recover the missing information, achieving a balance between speed and image quality
Solution Approach 2:
The patent performs preliminary acquisition of central k-space lines (low spatial frequencies) first, which contain the most important image information. This allows early image reconstruction with acceptable quality while remaining scan data is acquired, effectively reducing the perceived scan time for diagnostic purposes
2Measurement precision
If calibration data is determined after complete scan data acquisition, then comprehensive data is available for accurate calibration, but reconstruction time is delayed
Solution Approach 1:
The patent determines calibration data (such as coil sensitivity maps or ghost correction factors) from the centrally-acquired scan data before the entire k-space is filled. This preliminary calibration enables early image reconstruction with acceptable accuracy, while the remaining scan data continues to be acquired in the background
Solution Approach 2:
The patent segments the scan acquisition into phases: first acquiring central k-space lines for calibration and preliminary reconstruction, then acquiring peripheral lines. This segmentation allows independent processing of calibration data without waiting for complete data acquisition, reducing overall reconstruction delay
3Speed
If gradient coils operate at high speed for wave techniques, then scan time is reduced, but eddy currents cause deviations and artifacts
Solution Approach 1:
The patent measures actual gradient coil performance and determines calibration data that captures deviations caused by eddy currents and other imperfections. This calibration data is then used in the reconstruction process to correct artifacts, enabling high-speed gradient switching while maintaining image quality
Solution Approach 2:
The patent converts the harmful effect of gradient deviations and eddy currents into useful calibration information. By measuring and characterizing these deviations during the scan, the system transforms what would be sources of artifacts into corrective data that improves reconstruction accuracy at high gradient speeds
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 time needed for calibration data determination, allowing for earlier image reconstruction and improving the quality of reconstructed images by addressing gradient imperfections and aliasing artifacts.
Implementation Method 1
to trigger nuclear spin resonances that can be measured as signals, radio frequency excitation pulses (RF pulses) are radiated into the examination object
Implementation Method 2
For spatial encoding of the scan data, rapidly-switched magnetic gradient fields, known as gradients, are overlaid onto the main magnetic field
Implementation Method 3
the nuclear spin resonances produced are measured as so-called k-space data
Data Source
AI summary
Calibration data is determined for a reconstruction of image data from scan data acquired via a magnetic resonance system. This includes specifying acquisition shots for an acquisition of desired scan data in which acquisition shots scan data is acquired after radiating-in an RF excitation pulse, identifying first acquisition shots among the acquisition shots specified in which scan data is acquired in a central region in k-space, stipulating a sequence in which the specified acquisition shots are to be carried out such that first acquisition shots are arranged in the sequence in a starting portion to be carried out first, acquiring the scan data by carrying out the specified acquisition shots in the stipulated sequence, determining calibration data from scan data acquired in the starting portion of the sequence, and reconstructing image data using the acquired scan data and the specified calibration data.