Curved Collimator Slit Profile for Rectangular CT Projection
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Solution Overview
Problem
Conventional CT collimators, with either linear or curved slit profiles, face challenges in maintaining detection accuracy while minimizing additional radiation dose to the subject, due to irregular projection shapes and production difficulties.
Innovation Solution
A CT imaging system with a collimator featuring a planar gating device and slits, where the slit width distribution is determined by the vertical distances, inclination angles, detector element lengths, and offset angles, ensuring a rectangular projection distribution on the detector, thereby avoiding radiation over-shoot and under-shoot areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional linear slit collimator is used, then the collimator structure is simple and easy to manufacture, but the projection range forms an irregular rectangular shape reducing detection accuracy and causing additional radiation dose
Solution Approach 1:
The patent applies curvature to the collimator slit profile, transforming it from a linear shape to a curved shape that matches the arc surface geometry of the X-ray detector. This curved slit profile ensures that the projection range forms a regular rectangular shape on the detector, thereby improving detection accuracy while eliminating over-shoot and short-shoot areas that cause additional radiation dose. The curved design maintains manufacturing feasibility by using standardized arc surfaces centered on the X-ray tube focus.
2Measurement precision
If a curved slit collimator is used, then the projection range forms a regular rectangular shape improving detection accuracy, but the production difficulty and cost increase significantly
Solution Approach 1:
The patent makes the collimator slit profile universal by designing it to match the standardized arc surface geometry of the X-ray detector, which is centered on the X-ray tube focus. This universal curved profile design allows the collimator to work effectively with standard arc-shaped detectors, achieving regular rectangular projection ranges and improved detection accuracy while maintaining manufacturing feasibility through standardized geometric relationships.
3Adaptability or versatility
If a plate type collimator with general formula slit profile is used, then the projection is close to the detector profile, but large over-shoot and short-shoot areas exist causing additional radiation dose
Solution Approach 1:
The patent applies local quality by precisely designing the collimator slit profile to match the specific geometric characteristics of the X-ray detector at different locations. The curved slit width distribution is calculated based on the arc surface geometry and detector element positions, ensuring that each region of the collimator produces the optimal projection shape for its corresponding detector area. This localized optimization eliminates over-shoot and short-shoot areas throughout the entire projection range, preventing additional radiation dose to the subject.
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 allows for precise determination of the collimator slit profile, achieving ideal projection distribution without additional radiation dose and maintaining detection accuracy, even with apparatus installation deviations.
Implementation Method 1
a collimator disposed between the subject and the radiation source for beamforming the radiation rays from the radiation source before projecting them to the subject
Implementation Method 2
a radiation detector disposed on the scan gantry and at the other side of the subject for detecting the radiation rays transmitted through the subject
Data Source
AI summary
A CT imaging system and a method for determining a CT collimator slit profile. The method includes determining a profile of two opposite edges of the collimator slit in a longitudinal direction thereof based on the following: a vertical distance between a focus of a radiation source to the collimator slit, a vertical distance between the focus and the radiation detector, an inclination angle between adjacent detector elements, a length of each detector element, a desired width of projection on the radiation detector by the radiation rays passing through the slit whose longitudinal edge profile is to be determined, and an offset angle of a connecting line from a point on a longitudinal center line of the slit to the focus relative to a plane passing said focus and perpendicular to the slit.