Radiographic Offset Correction Using Variable Accumulation Time

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Solution Overview

Problem

In X-ray imaging systems, the accuracy of offset correction for radiographic images is compromised due to changes in dark current noise caused by temperature fluctuations during calibration, leading to potential inaccuracies in noise removal and image quality.

Innovation Solution

A radiographic image detection device and method that acquire multiple offset images with different accumulation times and a reference image to determine the validity of offset images for correction, reacquiring them if the correction error exceeds a threshold, ensuring accurate noise removal and improved image quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If offset data is acquired immediately before X-ray imaging, then the accuracy of offset correction is improved, but a time lag occurs between the instruction to perform X-ray imaging and the actual imaging

Engineering Contradiction:

Improveaccuracy of offset correctionVSAvoidtime lag before imaging

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary acquisition of offset data during calibration periods (when no X-ray imaging is performed) and stores multiple offset images with different accumulation times. This allows the system to have offset correction data ready in advance, eliminating the time lag while maintaining correction accuracy through selective use of appropriate offset images.

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If offset data is acquired during calibration, then the time lag is reduced, but temperature changes during calibration cause dark current noise variations that reduce correction accuracy

Engineering Contradiction:

Improvetime lag before imagingVSAvoidaccuracy of offset correction

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

The system changes the accumulation time parameter of offset images based on temperature conditions and imaging conditions. By acquiring multiple offset images with different accumulation times during calibration and selecting the appropriate one based on actual imaging parameters, the system maintains correction accuracy despite temperature variations during calibration.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The offset correction process is segmented into multiple offset images acquired at different accumulation times during calibration. This segmentation allows the system to handle temperature variations by selecting the most appropriate offset image segment that matches the actual imaging conditions, thereby maintaining correction accuracy.

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If multiple offset images with different accumulation times are acquired, then the accuracy of noise correction is improved by accounting for temperature variations, but the complexity of the calibration process increases

Engineering Contradiction:

Improveaccuracy of noise correctionVSAvoidcomplexity of calibration process

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system dynamically selects the appropriate offset image from multiple pre-acquired images based on actual imaging conditions such as accumulation time and temperature. This dynamic selection approach maintains high correction accuracy while avoiding the need to process all calibration images, thereby managing complexity through adaptive rather than exhaustive processing.

Inventive Principle:

Principle #15Dynamics

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 allows for precise determination of when to reacquire offset images, maintaining high accuracy in noise correction and image quality by accounting for temperature-induced dark current noise variations.

Implementation Method 1

an X-ray imaging system that uses, for example, X-rays as radiation... an X-ray image detection device that detects an X-ray image based on the X-rays transmitted through the subject

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

Of the dark current noise and the fixed pattern noise included in the offset data, the dark current noise changes depending on the temperature

Methodology Applied

Scientific EffectThermal generation of dark current: Thermal Radiation

Data Source

PatentUS11432784B2Radiographic image detection device, method for operating radiographic image detection device, and program for operating radiographic image detection device

Publication Date: 2022.09.06 FUJIFILM CORP

AI summary

At least two first offset images having different accumulation times are acquired in a state in which radiation is not emitted. A pixel signal is read in an accumulation time shorter than that of a plurality of first offset images or using binning reading in a state in which the radiation is not emitted to acquire a second offset image. A reference image is acquired by reading the pixel signal using the same reading method as that used for the second offset image and in a state in which gates of the pixels are turned off. A difference between the two first offset images having different accumulation times is calculated to acquire a first dark current distribution image. A difference between the second offset image and the reference image is calculated to acquire a second dark current distribution image. It is determined whether or not reacquisition is needed on the basis of a correction error of a corrected image obtained by correcting the first dark current distribution image on the basis of the second dark current distribution image.