Computed Radiography Detector Spatial Response Signature Removal
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Solution Overview
Problem
Computed radiography (CR) systems suffer from diagnostic image quality loss due to local sensitivity variability in x-ray detectors, which introduces a detector-specific spatial response signature that pollutes patient information and reduces Detective Quantum Efficiency (DQE), making it difficult to discern subtle image details and potentially hiding pathology.
Innovation Solution
A method to remove the spatial response signature of a photo-stimulable phosphor detector from radiographic images by retrieving and adapting the unique image plate signature, performing adaptive filtering and normalization, and using virtual markers for sub-pixel accurate spatial registration and demodulation to create a uniform dose-sensitivity representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detector's spatial response signature is present in the image, then the detector can capture and store latent shadow image information, but the detector's local sensitivity variability introduces noise that reduces image quality and detection capabilities
Solution Approach 1:
The patent extracts and removes the detector's spatial response signature (IPS) from the acquired image through digital processing. The IPS is identified as the medium to high spatial frequency components of the relative sensitivity distribution, and these components are separated and eliminated from the image data, leaving only the relevant patient information.
Solution Approach 2:
The patent applies parameter changes by modifying the frequency domain characteristics of the image. Through Fourier transformation and filtering operations, the spatial frequency parameters are adjusted to remove the IPS components while preserving the diagnostic information, effectively changing the image's frequency spectrum to eliminate noise.
2Reliability
If the detector structure is used to capture x-ray information, then the latent shadow image can be stored, but the medium to high spatial frequency components of the sensitivity distribution create artifacts that hide pathology
Solution Approach 1:
The patent converts the harmful effect of the detector structure by measuring and characterizing the IPS in advance during detector manufacturing or calibration. This measured IPS profile is then used as a reference to identify and remove the same structural artifacts from clinical images, turning the detector's inherent structural signature from a harmful artifact source into a useful reference for artifact removal.
Solution Approach 2:
The patent performs preliminary characterization of the detector's spatial response signature before actual patient imaging. The IPS is measured and stored as reference data during detector manufacturing or initial calibration, enabling subsequent removal of these artifacts from clinical images without requiring repeated measurements.
3Ease of manufacture
If the image plate sensitivity varies locally across the surface, then the detector can be manufactured with standard tolerances, but the sensitivity variability watermarks the image and reduces radiologist confidence
Solution Approach 1:
The patent introduces a digital processing intermediary that mediates between the detector's inherent sensitivity variability and the final image output. The IPS removal algorithm acts as this intermediary, processing the raw image data to eliminate the watermarking effect of local sensitivity variations while preserving the underlying patient information, thus bridging the gap between manufacturing tolerances and diagnostic quality.
4Productivity
If the detector's spatial response signature is not removed, then the image acquisition process is simple, but the Detective Quantum Efficiency is diminished and reading comfort is reduced
Solution Approach 1:
The patent performs preliminary measurement and characterization of the detector's spatial response signature during manufacturing or initial calibration, storing this IPS profile for later use. This preliminary action enables rapid IPS removal processing during clinical operation, as the reference data is already available, thus maintaining fast image acquisition while enabling subsequent DQE improvement through artifact removal.
Data Source
AI summary
Method of removing the spatial response signature of a detector from a computed radiography image by adaptively filtering and spatially warping the characteristic response signature of the detector prior to demodulation.