Beam Hardening Correction for CT Eccentric Scan Artifacts

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Solution Overview

Problem

Existing CT systems face challenges in accurately correcting beam hardening artifacts, particularly in eccentric scans, which lead to band-shaped artifacts and misinterpretation of images, especially in high-density materials like bone.

Innovation Solution

A method and device that acquire an original reconstructed image and sinogram, process them to reduce errors, calculate average values, optimize the sinogram to determine a coefficient vector, and fit it to obtain a beam hardening correction coefficient, effectively addressing beam hardening corrections across various object sizes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If existing beam hardening correction techniques are applied to aligned scans, then uniformity is improved, but band-shaped artifacts still appear in eccentric scans

Engineering Contradiction:

Improveimage uniformityVSAvoidapplicability to eccentric scans

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the parameter of scan position adaptation by developing correction coefficients specifically for eccentric scans. The method involves acquiring sinogram data from eccentric scans, processing it through error reduction and optimization to determine correction coefficients that account for the specific geometry and beam hardening effects of eccentric positioning, thereby eliminating band-shaped artifacts while maintaining uniformity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If polychromatic X-rays are used for imaging, then imaging capability is improved, but beam hardening effect causes grey scale value shift and image distortion

Engineering Contradiction:

Improveimaging capabilityVSAvoidgrey scale accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces the need for physical beam hardening correction filters or hardware modifications with a computational approach. By processing sinogram data through error reduction algorithms and optimization functions, the system calculates correction coefficients that mathematically compensate for beam hardening effects, thereby maintaining grey scale accuracy without altering the polychromatic X-ray imaging capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If beam hardening correction is performed using conventional methods, then processing speed is maintained, but correction accuracy for high-density materials is insufficient

Engineering Contradiction:

Improveprocessing speedVSAvoidcorrection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent performs preliminary processing of sinogram data through error reduction and optimization steps before final image reconstruction. By pre-calculating correction coefficients from processed sinogram data that has already undergone error reduction, the system prepares accurate correction factors in advance, which are then applied during reconstruction to achieve high correction accuracy for high-density materials without compromising processing speed.

Inventive Principle:

Principle #10Preliminary action

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 significantly reduces or eliminates band-shaped artifacts, providing more accurate and uniform images, improving diagnostic clarity by correcting beam hardening effects in CT data.

Implementation Method 1

during CT X-ray imaging of a patient by a CT system, X-rays are used for imaging the features of inner structures and regions of interest (ROI) of the patient body

Methodology Applied

Scientific EffectX-ray: X-Ray

Implementation Method 2

in the case of polychromatic X-rays, it will be viewable that average energy of X-rays emitted by a penetrated object shifts to a higher energy value. This effect is called 'beam hardening'

Methodology Applied

Scientific EffectBeam hardening: Absorption (EM radiation)

Data Source

PatentUS9715744B2Method and device of obtaining beam hardening correction coefficient for carrying out beam hardening correction on computed tomography data

Publication Date: 2017.07.25 GE MEDICAL SYSTEMS GLOBAL TECHNOLOGY CO LLC

AI summary

The present invention relates to a method and device of obtaining a beam hardening correction coefficient for carrying out beam hardening correction on computed tomography data. The method includes the steps of: firstly, acquiring an original reconstructed image and an original sinogram of an object of a particular size; secondly, obtaining an error-reduced sinogram after processing the original reconstructed image by error reduction; thirdly, sampling and calculating an average value of the original sinogram and an average value of the error-reduced sinogram; fourthly, optimizing the original sinogram according to the error-reduced sinogram to determine a coefficient vector of optimization function for the object of the particular size; and finally fitting the coefficient vector of the optimization function of the original sinogram to obtain the beam hardening correction coefficient for the object of the particular size.