CT Image Reconstruction Scatter Correction Model
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Solution Overview
Problem
Conventional computed tomography (CT) image reconstruction methods, such as filtered back-projection, suffer from low-frequency cone beam artifacts and helical artifacts, and are limited by the trade-off between image sharpness and noise, while dual-source CT systems face issues with scattered radiation, including forward and cross scattering, which degrade image quality.
Innovation Solution
A method for reconstructing CT images that calculates and corrects scatter signals using an angle-dependent scattered radiation model, allowing for the reduction of undesirable artifacts by accounting for scatter distribution and attenuation integrals, thereby improving image data quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional filtered back-projection methods are used for CT image reconstruction, then the reconstruction process is simple and fast, but low-frequency cone beam artifacts and helical artifacts occur, and image sharpness is coupled to image noise
Solution Approach 1:
The patent segments the reconstruction process into multiple steps: initial image reconstruction using FBP, scatter signal calculation from the initial image, correction of measurement data by subtracting scatter signals, and final image reconstruction. This segmentation allows the use of fast FBP while addressing its limitations through additional processing stages.
Solution Approach 2:
The patent performs preliminary scatter signal calculation from the initially reconstructed image before final image reconstruction. By estimating and removing scatter effects in advance, the method prepares corrected measurement data that leads to higher quality final images without sacrificing reconstruction speed.
2Productivity
If the number of detector rows is increased to improve scanning coverage, then the scanning efficiency is improved, but scattered radiation increases causing forward scattering artifacts
Solution Approach 1:
The patent converts the harmful scattered radiation into a measurable signal by calculating scatter signals from the initially reconstructed image using a scatter model. These calculated scatter signals, which represent the harmful effect, are then subtracted from the measurement data to produce corrected data, thereby converting the harmful scatter into a correctable component.
Solution Approach 2:
The patent introduces a scatter model as an intermediary between the measurement data and the final image reconstruction. This model estimates the scatter component based on the initial image and geometry, acting as a mediator that separates the useful primary radiation signal from the harmful scattered radiation, allowing for selective correction.
3Speed
If dual-source CT systems operate both x-ray sources simultaneously to halve data acquisition time, then temporal resolution is improved, but cross scattering between sources increases causing additional artifacts
Solution Approach 1:
The patent uses a scatter model as an intermediary to estimate and separate cross-scatter contributions from the measurement data of each source. By calculating scatter signals based on the initial image and geometric relationships between sources and detectors, the method identifies and removes cross-scatter artifacts while preserving the temporal resolution benefits of simultaneous dual-source operation.
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
The method effectively reduces imaging artifacts caused by scattered radiation, leading to improved image data with reduced noise and enhanced sharpness, particularly beneficial for dual-source CT systems by addressing both forward and cross scattering.
Implementation Method 1
an x-ray quantum, instead of being absorbed by the examination object, is scattered, i.e. deflected in terms of its direction
Implementation Method 2
a line integral corresponding to an attenuation integral of a scattered beam from the scatter point to a specific detector element
Data Source
AI summary
A method is disclosed for reconstructing image data of an examination object from measurement data, wherein the measurement data were acquired in the course of a relative rotational movement between a radiation source of a computed tomography system and the examination object. First image data of the examination object are reconstructed from the measurement data. Scatter signals are calculated from the first image data using a scattered radiation model, wherein the scattered radiation model specifies an angle-dependent scatter distribution for a scatter point as a function of a line integral corresponding to an attenuation integral of a scattered beam from the scatter point to a specific detector element. The calculated scatter signals are used for correcting the measurement data, and second image data are reconstructed using the corrected measurement data.