MRI Calibration Image Acquisition for Off-Resonance Artifact Reduction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) techniques face challenges with image artifacts due to off-resonance effects, particularly at high field strengths, which are difficult to combat using conventional calibration methods, especially in organs with periodic movement like the heart.
Innovation Solution
A method for acquiring and displaying calibration images in a periodically moving organ using magnetic resonance technology, where multiple calibration images with varying offset frequencies and spatial positions are acquired during a continuous period, allowing for faster acquisition and improved selection of the ideal offset frequency for diagnostic image optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration images are acquired one per heartbeat over a breath-hold phase with varied offset frequencies, then the ideal offset frequency can be selected to reduce off-resonance artifacts, but the acquisition time is extended and the process is time-consuming
Solution Approach 1:
The system performs preliminary acquisition of multiple calibration images with different offset frequencies during a single continuous period of organ movement. This preliminary action allows the ideal offset frequency to be selected before diagnostic image acquisition, reducing artifacts while avoiding extended total examination time by consolidating all calibration acquisitions into one continuous period rather than spreading them across multiple heartbeats
Solution Approach 2:
The system dynamically adapts the calibration image acquisition by capturing multiple images with varying offset frequencies and spatial positions within a single organ movement period. This dynamic approach allows flexible selection of optimal parameters based on actual organ position and movement phase, improving measurement precision without the time penalty of sequential heartbeat-based acquisition
2Reliability
If multiple calibration images with different offset frequencies are acquired across multiple heartbeats, then artifact reduction is achieved, but the complexity of the acquisition process increases
Solution Approach 1:
The system merges the acquisition of multiple calibration images with different offset frequencies and spatial positions into a single continuous acquisition period. By combining these acquisitions that would traditionally occur across multiple heartbeats into one unified process, the system reduces procedural complexity while maintaining the ability to select optimal parameters for high-quality diagnostic imaging
Solution Approach 2:
The calibration image acquisition system is designed to simultaneously acquire images with multiple offset frequencies and spatial positions within a single organ movement period. This multi-functional approach allows the system to gather comprehensive calibration data across different parameters in one unified acquisition, reducing the complexity of managing separate acquisition sequences for each parameter
3Ease of operation
If calibration images are acquired with fixed spatial positions and offset frequencies per heartbeat, then the acquisition protocol is simple, but the flexibility to optimize for different organ positions and frequencies is limited
Solution Approach 1:
The system dynamically varies both the spatial position and offset frequency of calibration images acquired during a single organ movement period. This dynamic protocol maintains operational simplicity by automating the variation of parameters within the acquisition sequence, while simultaneously providing high flexibility to optimize calibration for different organ positions and frequency requirements without requiring complex manual protocol adjustments
4Measurement precision
If the offset frequency is varied in equal steps across heartbeats, then the frequency range is systematically covered, but the acquisition speed is reduced
Solution Approach 1:
The system performs preliminary acquisition of calibration images covering the full frequency range and spatial positions within a single continuous period. This preliminary action systematically covers the required frequency range with equal steps while maintaining high acquisition speed by utilizing the continuous organ movement period, avoiding the time-consuming sequential heartbeat-based approach
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 enables the acquisition of higher-quality diagnostic images by increasing flexibility in testing offset frequencies and spatial positions, reducing the impact of organ movement phases on selecting optimal frequencies, thus improving image quality and reducing artifacts.
Implementation Method 1
nuclear spins in the subject orient along the basic magnetic field. Radio-frequency excitation pulses are radiated into the examination subject to excite nuclear magnetic resonances, the resonant nuclear spin signal is measured
Implementation Method 2
For spatial coding of the measurement data, rapidly switched gradient fields are superimposed on the basic magnetic field
Implementation Method 3
By means of a multidimensional Fourier transformation, an associated MR image can be reconstructed from the k-space matrix populated with such values
Data Source
AI summary
In a method and magnetic resonance apparatus to acquire and present calibration images of a periodically moving organ with the use of magnetic resonance technology, calibration images are acquired by acquiring measurement data for multiple calibration images during one continuous period of the organ movement, the multiple calibration images differing in their offset frequency and/or in their spatial position in the organ to be examined, and the calibration images in a presentation manner that, from the visual quality of the respective images, allows the user to select (identify) the image acquired with the offset frequency that should then be used to acquire the diagnostic image are displayed to a user.