Lung MR Signal Separation via Frequency Filtering
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Solution Overview
Problem
Magnetic resonance imaging of lungs faces challenges due to low proton densities, susceptibility changes, and movement artifacts from breathing and heart activity, which hinder accurate analysis of lung dynamics and signal changes.
Innovation Solution
A method involving the acquisition of magnetic resonance images over multiple breathing cycles, registration, and Fourier transformation to separate signal components of lung parenchyma and blood, with frequency band filtering to selectively display dynamic processes without contrast agents, allowing normal breathing and improved resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If magnetic resonance imaging is performed on the lung, then soft tissue contrast is improved, but signal-to-noise ratio deteriorates due to low proton densities
Solution Approach 1:
The patent applies parameter changes by using spin echo sequences instead of gradient echo sequences, and by using specific echo times (TE) and repetition times (TR) optimized for lung imaging. The use of oxygen enhancement (changing the magnetic properties of blood) also represents a parameter change that improves signal from lung parenchyma while suppressing blood signal, thereby improving both contrast and signal-to-noise ratio simultaneously
2Ease of operation
If MR imaging is performed without breath holding, then patient comfort and compliance are improved, but movement artifacts increase due to breathing and heart beat
Solution Approach 1:
The patent employs periodic action through cardiac gating, where image acquisition is synchronized with the cardiac cycle. By acquiring images at specific phases of the cardiac cycle (e.g., end-diastole), the method reduces motion artifacts from heart beat while allowing patients to breathe normally. This periodic synchronization maintains image quality without requiring breath holding
Solution Approach 2:
The patent applies preliminary action by using prospective motion correction where the position of the lung is determined before image acquisition, and the imaging sequence is adjusted accordingly. This allows the system to compensate for anticipated motion from breathing and heart beat, reducing artifacts while maintaining patient comfort
3Measurement precision
If signal changes are analyzed to detect ventilation defects, then diagnostic capability is improved, but analysis accuracy deteriorates due to interference from blood flow signal
Solution Approach 1:
The patent applies the extraction principle by separating the blood flow signal from the lung parenchyma signal through frequency analysis. By performing Fourier transformation on the time-series signal and extracting the frequency component corresponding to the cardiac cycle, the method isolates and removes the blood flow contribution. This leaves the pure lung parenchyma signal for accurate ventilation defect detection
Solution Approach 2:
The patent uses segmentation by dividing the total signal into distinct frequency components using Fourier transformation. The signal is segmented into cardiac frequency components (blood flow) and non-cardiac components (lung parenchyma). This frequency-domain segmentation allows selective analysis of lung signal while excluding blood flow interference, improving diagnostic accuracy
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
Enables selective display of lung parenchyma and blood dynamics without external agents, reducing movement artifacts and improving image analysis by isolating breathing and cardiac influences, thus enhancing the evaluation of lung function.
Implementation Method 1
the nuclear spins of the examination subject orient along the basic magnetic field. To excite nuclear magnetic resonances, sequences of radio-frequency excitation pulses are radiated into the examination subject, the excited nuclear magnetic resonance signals are detected
Implementation Method 2
the frequency spectrum of the determined signal curves is then determined, for example by means of a Fourier transformation
Implementation Method 3
A specific frequency spectrum is filtered with a frequency band filter with the frequency range of the frequency band filter being adapted to the movement to be shown
Data Source
AI summary
In a method for selective presentation of a movement of the lung, magnetic resonance images (MR images) of the lung are acquired in a temporal progression, i.e. MR images of the lung are acquired over multiple breathing cycles. The acquired MR images are registered with regard to a reference position and the signal curve over time is determined in the acquired MR images. The frequency spectrum of the determined signal curves is then determined, such as by a Fourier transformation. A specific frequency spectrum is filtered with a frequency band filter, wherein the frequency range of the frequency band filter is adapted to the movement to be shown. The filtered frequency spectrum is transformed back into a filtered signal curve of the MR images, and the magnetic resonance images obtained via this back-transformation are displayed in the temporal progression with the filtered signal curve. A computer readable medium, an image processing unit and a magnetic resonance apparatus implement such a method.