CT Scatter Correction via Prior Image Registration
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Solution Overview
Problem
Computed tomography (CT) projection data is often contaminated by scatter radiation signals, leading to decreased image contrast, CT number accuracy, and severe cupping artifacts, which limits the use in dose calculation and tumor delineation for adaptive radiation therapy.
Innovation Solution
A system and method that process projection data by obtaining a first image from a multi-detector CT device, registering it with cone-beam CT data, determining the scatter component, and subtracting it to generate corrected projection data, using energy spectra and detector energy responses to isolate primary radiation signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If CT projection data is acquired using a large radiation field of view, then the coverage area is increased, but scatter radiation signals contaminate the data
Solution Approach 1:
The patent segments the projection data into primary radiation signals and scatter radiation signals through registration with a prior scatter-free image. By dividing the contaminated projection data into separable components, the system can selectively correct the scatter portion while preserving the primary signal information.
Solution Approach 2:
The patent introduces a prior scatter-free image as an intermediary reference to facilitate scatter correction. This reference image serves as a mediator that enables the separation and identification of scatter components in the contaminated projection data through image registration techniques.
2Area of stationary object
If scatter radiation signals are present in projection data, then image coverage is maintained, but image contrast decreases
Solution Approach 1:
The patent extracts scatter radiation signals from the contaminated projection data by registering with a prior scatter-free image. This extraction process isolates the scatter component, allowing it to be removed or corrected while preserving the primary radiation signals that carry the diagnostic image information.
3Ease of operation
If scatter radiation signals contaminate projection data, then data acquisition is simplified, but CT number accuracy decreases
Solution Approach 1:
The patent employs a feedback mechanism where a prior scatter-free image is used to evaluate and correct scatter contamination in new projection data. The registered scatter-free image provides reference information that feeds back into the correction process, enabling iterative refinement of scatter correction and improvement of CT number accuracy.
4Productivity
If scatter radiation signals are present, then imaging process is faster, but cupping artifacts increase
Solution Approach 1:
The patent performs preliminary scatter correction by registering a prior scatter-free image with the current contaminated projection data before final image reconstruction. This preliminary action removes scatter artifacts in advance, preventing cupping artifacts from developing during reconstruction while maintaining efficient imaging speed.
Data Source
AI summary
The present disclosure provides a method for processing projection data. The method may include obtaining a first image generated by performing a first scan to a subject by a first imaging device; determining first projection data based on the first image, the first projection data corresponding to a first area of the subject; obtaining second projection data by performing a second scan of the subject using a second imaging device, the second projection data corresponding to a second area of the subject, the first area at least partially overlapping with the second area in an overlapping area; determining registered first projection data by registering the first projection data to the second projection data with respect to the overlapping area; determining scatter component based on the registered first projection data and the second projection data, the scatter component including low-frequency scattered radiation signals.