X-ray Diagnostic Apparatus Third Harmonic Moiré Removal
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Solution Overview
Problem
Conventional X-ray diagnostic apparatuses face issues with residual moiré patterns in images after removal, primarily due to errors in grid density, leading to visibility degradation and incomplete removal of harmonics.
Innovation Solution
An X-ray diagnostic apparatus and storage medium program that detect and remove the third harmonic of the moiré pattern by calculating its peak frequency, generating a corresponding filter, and subtracting it from the image, while selectively outputting the third harmonic removed image in flat regions and the first and second harmonic removed image in non-flat regions to maintain image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first and second harmonics are removed from the moiré pattern, then the moiré pattern is partially removed, but the third harmonic remains causing residual moiré patterns and visibility degradation
Solution Approach 1:
The patent segments the moiré pattern removal process into distinct stages: first removing the first and second harmonics, then separately detecting and removing the third harmonic. This segmentation allows each harmonic to be addressed with appropriate filtering techniques, ensuring complete removal without leaving residual patterns that would degrade visibility.
Solution Approach 2:
The patent changes the frequency parameter by detecting the peak frequency of the third harmonic and applying a filter specifically tuned to this frequency. By adjusting the filter parameters based on the detected peak frequency, the system effectively removes the third harmonic while preserving other important image frequencies.
2Object-generated harmful factors
If a filter is applied to remove the third harmonic, then the residual moiré pattern is removed, but image details may be lost due to over-filtering
Solution Approach 1:
The patent replaces broad mechanical filtering with a targeted approach: first detecting the specific peak frequency of the third harmonic through Fourier transform analysis, then applying a filter only at this detected frequency. This substitution of generic filtering with frequency-specific filtering removes the harmful third harmonic while preserving other image details that would otherwise be lost.
Solution Approach 2:
The system uses feedback by detecting the peak frequency of the third harmonic and using this information to adjust the filter parameters. This feedback mechanism ensures that the filter is precisely tuned to remove only the third harmonic frequency while leaving other frequencies intact, thus preserving image details.
3Reliability
If the grid density is increased to reduce moiré pattern, then the grid effectiveness improves, but the difference between grid density and detector resolution increases causing more pronounced moiré patterns
Solution Approach 1:
The patent extracts and removes the harmful moiré pattern frequencies (first, second, and third harmonics) from the image after acquisition. By taking out these specific frequency components through Fourier transform and targeted filtering, the system eliminates the moiré pattern effect regardless of the grid-detector density relationship, allowing the grid to maintain high effectiveness without being constrained by density matching requirements.
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
Effectively removes residual moiré patterns, particularly the third harmonic, from X-ray images, enhancing image visibility by distinguishing and subtracting the third harmonic in flat regions and preserving image details in non-flat regions, thus improving the image's clarity and signal-to-noise ratio.
Implementation Method 1
The grid 105 is formed by absorbers (e.g., lead) and transmission elements (e.g., aluminum or air) arranged alternately, the absorbers absorbing X-rays and the transmission elements transmitting X-rays. In the grid 105, the absorbers absorb X-rays scattered and entering obliquely
Implementation Method 2
an X-ray detector (e.g., a flat panel X-ray detector (FPD)) 104 that detects X-rays transmitting through the subject M
Implementation Method 3
First, one-dimensional Fourier transform is performed to the image with the moiré pattern appearing therein. Then, in accordance with results from the Fourier transform, a peak frequency representing the first harmonic in the moiré pattern is detected
Data Source
AI summary
An X-ray diagnostic apparatus includes a peak frequency detector detecting a peak frequency of a first harmonic in a moiré pattern of a grid in an image; a harmonic remover removing the first harmonic and a second harmonic in the moiré pattern from the image in accordance with the peak frequency of the first harmonic to obtain a first and second harmonic removed image; a harmonic extracting-filter generating unit calculating a peak frequency of a third harmonic in the moiré pattern in accordance with the peak frequency of the first harmonic to generate a harmonic extracting filter to extract the third harmonic; a harmonic extracting unit extracting the third harmonic from the first and second harmonic removed image based on the harmonic extracting filter; and a harmonic subtracting unit subtracting the extracted third harmonic from the first and second harmonic removed image to obtain a third harmonic removed image.