Virtual X-ray Projection via Attenuation Modification
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Solution Overview
Problem
X-ray projection recordings from CT data sets lack comparable gray values to real X-ray projections due to differing emission spectra and are error-laden due to artifacts from sectional image reconstruction and corrections, leading to suboptimal image quality and increased patient dose.
Innovation Solution
A method that modifies local X-ray attenuation values in CT data sets to simulate a virtual X-ray projection by forward-projecting the modified data set onto a virtual detector, accounting for a virtual projection geometry, and transforming intensity values into scan values for an image matrix, thereby generating X-ray projections with improved gray-value distribution and increased information content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If X-ray projection recordings are generated from CT data sets using classic reconstruction methods, then the projection data can be obtained, but the gray values are not comparable to real X-ray projections and contain artifacts from reconstruction and corrections
Solution Approach 1:
The patent modifies the image data set by changing physical parameters - specifically replacing local X-ray attenuation values with modified values that account for the polychromatic emission spectrum of the X-ray tube. This involves energy-dependent attenuation coefficients and simulating the actual X-ray quantum energy distribution to produce gray values comparable to real X-ray projections
Solution Approach 2:
The patent introduces a virtual X-ray radiation detector as an intermediary element. This virtual detector simulates the signal chain of an actual detector, including energy-dependent detection efficiency and conversion to scan values, thereby mediating between the CT data and the final projection image to achieve realistic gray-value distribution
2Loss of information
If additional X-ray projection recordings are taken for topograms, then useful projection data is obtained, but the patient dose is increased
Solution Approach 1:
The patent creates a virtual copy of the X-ray projection process by forward-projecting the modified image data set onto a virtual detector. This virtual projection copying eliminates the need for additional physical X-ray exposures while preserving all necessary projection information, thereby reducing patient dose without sacrificing diagnostic value
3Measurement precision
If the emission spectrum of the X-ray tube is taken into account for accurate attenuation values, then gray-value accuracy improves, but the computational complexity increases
Solution Approach 1:
The patent performs preliminary modifications to the image data set before the forward projection step. By pre-calculating and storing modified X-ray attenuation values that incorporate emission spectrum effects, the complex energy-dependent calculations are done in advance, allowing the actual projection process to use these pre-prepared values and reducing real-time computational complexity
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 produces X-ray projections with gray-value distributions similar to real X-ray projections and increased information content, reducing patient dose and improving image quality by accurately simulating the signal chain of actual X-ray projections.
Implementation Method 1
The X-ray radiation emitted by the X-ray radiation source passes through a patient to be investigated and is attenuated by interaction with the different tissue types of the patient
Implementation Method 2
The detector is arranged behind the patient in relation to the X-ray radiation source, absorbs the X-ray radiation remaining behind the patient and converts it into the electrical signal corresponding to the X-ray attenuation caused by the patient
Implementation Method 3
at least one local X-ray attenuation value is replaced by a modified X-ray attenuation value
Implementation Method 4
a modified projection data set is generated by forward projection of the modified image data set to a virtual X-ray radiation detector, taking account of a virtual projection geometry
Data Source
AI summary
An embodiment relates to a method for generating a virtual X-ray projection of at least one body region of a patient to be imaged with an X-ray imaging device, a machine-readable data carrier and/or an X-ray imaging device. The method includes acquiring at least one projection data set representing the at least one body region of the patient to be imaged; reconstructing an image data set from the at least one projection data set, the image data set representing local X-ray attenuation values in the at least one body region; replacing at least one local X-ray attenuation value by a modified X-ray attenuation value; forward projecting the modified image data set onto a virtual X-ray radiation detector; calculating intensity values for a plurality of detector elements from the modified projection data set; transforming the calculated intensity values into scan values; and assigning the scan values to an image matrix.