Optimized Blocking Grating for Cone Beam CT Scattering Correction
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Solution Overview
Problem
Current cone beam CT image scattering correction methods, particularly those using blocking gratings, require multiple scans, increase patient exposure dose, and struggle with accurately extracting scattering signals in clinical settings due to isocenter deviation and vibration, limiting their clinical applicability.
Innovation Solution
A method and apparatus that optimize the blocking grating using a swinging model and mesh-adaptive direct search algorithm to establish optimized coordinates, allowing for accurate scattering signal extraction and correction in a single scan without source compensation, adaptable to clinical CBCT systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a blocking grating is used for scattering correction, then scattering artifacts are reduced, but multiple scans are required increasing patient exposure dose
Solution Approach 1:
The patent segments the scanning process into two distinct phases: a pre-scan phase where the blocking grating is positioned to collect scattering signal, and a main scan phase where the grating is removed to acquire projection data. This segmentation allows the scattering correction to be obtained without requiring multiple scans of the actual patient, thereby reducing patient exposure dose while still achieving scattering artifact correction.
Solution Approach 2:
The patent performs preliminary action by acquiring the scattering signal distribution in advance through a pre-scan with the blocking grating in place. This pre-acquired scattering information is then used to correct the main scan data, eliminating the need to repeat scans solely for scattering measurement and thus reducing patient dose.
2Loss of information
If a blocking grating is used for scattering correction, then scattering signal can be separated, but accurate extraction is difficult due to isocenter deviation and vibration
Solution Approach 1:
The patent applies dynamics by introducing a swinging model that accounts for the blocking grating's positional deviations caused by isocenter errors and vibrations. Instead of assuming a fixed grating position, the model dynamically adjusts the grating's angular and radial coordinates to compensate for these deviations, thereby maintaining accurate scattering signal extraction despite system instabilities.
Solution Approach 2:
The patent implements feedback through an optimization algorithm that iteratively adjusts the blocking grating's parameters based on the swinging model. The algorithm uses the relationship between the grating's position and the detected signal to refine the scattering signal extraction, compensating for deviations and improving measurement precision through continuous optimization.
3Device complexity
If traditional CT reconstruction theory is used, then computational simplicity is maintained, but scattering photons cannot be modeled leading to image quality deterioration
Solution Approach 1:
The patent introduces an intermediary approach by using a blocking grating to physically separate and measure the scattering signal, which is then used as a correction term in the traditional CT reconstruction process. This allows the simple and fast traditional reconstruction algorithms to be enhanced with scattering correction without requiring complex iterative reconstruction methods, thus maintaining computational simplicity while improving image quality.
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 optimized blocking grating design effectively corrects scattering artifacts, reducing CT errors from 115 HU to 11 HU and enhancing image contrast by 1.45 times, making it suitable for clinical cone beam CT applications.
Implementation Method 1
The scattered photons deviate from the incident beam direction and cannot be modelled into the traditional CT reconstruction theory
Implementation Method 2
The anti-scatter grid uses lead meshes focusing at the ray source and can block the scattered light from the non-focusing incident angle
Data Source
AI summary
A method and apparatus for optimizing a blocking grating for cone beam CT image scattering correction, wherein the method comprises: scanning a blocking grating to establish a swinging model thereof; setting initial coordinates of the blocking grating along a longitudinal direction of a detector in an initial projection, and establishing an objective function between CBCT image data missing voxel values and the coordinates of the blocking grating along the longitudinal direction of the detector according to the swinging model; minimizing the objective function with a mesh-adaptive direct search algorithm to generate optimized coordinates of the blocking grating along the longitudinal direction of the detector. The present disclosure proposes a brand new scattering correction method not requiring any source compensation, performs a mathematical optimization modeling of the data missing caused by the blocking grating in the image domain, quantitatively evaluates the influence on the reconstructed image by a blocker, solves a geometric optimal structure of the blocker using a mesh-adaptive direct search algorithm, and lays a solid theory foundation for the scattering correction method based on the blocker measurement.