CT Bowtie Filter with Depopulated Detector Array for Dose Reduction
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Solution Overview
Problem
Current CT imaging systems face challenges in dose reduction while maintaining image quality, particularly for cardiac and neural perfusion studies, as scanning with a larger field-of-view than necessary increases patient dose and costs without providing significant additional information, leading to truncation artifacts.
Innovation Solution
The implementation of a bowtie filter with x-ray filtration regions and an x-ray attenuation material positioned between the x-ray source and detector array, which attenuates x-rays outside the region-of-interest, combined with a method of using a depopulated detector array to reduce unnecessary radiation exposure, allowing for effective image reconstruction within the region-of-interest.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a larger field-of-view detector array is used to cover the entire region of interest, then image coverage is improved, but patient radiation dose increases
Solution Approach 1:
The detector array is divided into multiple independent detector modules that can be selectively activated. Only the detector modules corresponding to the region of interest are enabled during scanning, while other modules remain inactive. This segmentation allows the system to use a physically large detector array but activate only the necessary portion, thereby maintaining full FOV coverage capability while reducing the actual radiation exposure area to match the clinical need.
2Object-affected harmful factors
If a smaller field-of-view detector array is used to reduce dose, then radiation exposure is reduced, but truncation artifacts occur in image reconstruction
Solution Approach 1:
The system performs preliminary identification of the region of interest before the actual scanning process. Based on this pre-identified ROI, the system pre-configures which detector modules should be active and which should remain inactive. This preliminary setup ensures that when scanning begins, the exact necessary detectors are already positioned and activated, preventing any truncation of the ROI data while avoiding activation of detectors that would only increase dose without contributing useful information.
3Measurement precision
If all detector modules are activated to ensure complete data collection, then image reconstruction accuracy is improved, but system cost and complexity increase
Solution Approach 1:
The detector array transitions from a static configuration where all modules are permanently active to a dynamic configuration where detector module activation is adjusted based on the specific clinical examination requirements. The system can dynamically enable or disable detector modules depending on the region of interest for each patient study, optimizing the balance between data quality and resource utilization for each scanning scenario.
4Object-affected harmful factors
If x-ray attenuation material is added to the bowtie filter to reduce off-center radiation, then dose reduction is achieved, but system complexity and manufacturing cost increase
Solution Approach 1:
Instead of uniformly adding attenuation material across the entire bowtie filter, the system applies x-ray attenuation material selectively only to specific regions - namely, only to those detector modules that are inactive during the scan. This localized approach ensures that radiation is attenuated only where needed (in regions that won't contribute to the image anyway), while leaving the rest of the filter design simple and manufacturable. The attenuation material is positioned precisely where it provides benefit without complicating the overall filter structure.
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 patient dose by minimizing radiation outside the region-of-interest, while maintaining image fidelity through additional processing to estimate missing information, thus reducing the overall cost and complexity of the CT system.
Implementation Method 1
a first bowtie filter positioned between the x-ray source and the opening. The first bowtie filter includes a first x-ray filtration region positioned to attenuate x-rays that pass through an isochannel of the detector array, a second x-ray filtration region positioned to attenuate x-rays that pass through channels of the detector array that are offcenter in a channel direction from the isochannel
Implementation Method 2
an x-ray attenuation material positionable to attenuate the x-rays that pass through the channels of the detector array that are offcenter in the channel direction from the isochannel
Implementation Method 3
X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator
Implementation Method 4
photodiodes for receiving the light energy from the adjacent scintillator and producing electrical signals therefrom
Data Source
AI summary
A CT system includes an x-ray source configured to project an x-ray beam toward an object, a detector array, and a bowtie filter. The bowtie filter includes a first x-ray filtration region positioned to attenuate x-rays that pass through an isochannel of the detector array, a second x-ray filtration region positioned to attenuate x-rays that pass through channels of the detector array that are offcenter in a channel direction from the isochannel, and an x-ray attenuation material positionable to attenuate the x-rays that pass through the channels of the detector array that are offcenter in the channel direction from the isochannel. The CT system also includes a data acquisition system (DAS) connected to the detector array and configured to receive outputs from the detector array, and a computer programmed to acquire projections of imaging data of the object, and generate an image of the object using the imaging data.