Variable Stop Apparatus for CT Scanner Scattered Radiation
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Solution Overview
Problem
Computed tomography (CT) scanners face challenges in reducing scattered radiation, which increases signal noise and produces unwanted artifacts in images, particularly due to large X-ray beam angles and inhomogeneous illumination of the detector surface.
Innovation Solution
A variable stop apparatus with pivotable stops arranged at different longitudinal positions allows for optimal positioning of the stop size and distance from the focal spot, minimizing unsharpness and reducing the X-ray beam angle, thereby reducing scattered radiation and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a larger stop size is used to illuminate the entire sensor surface, then homogeneous illumination is achieved, but the used ray angle increases causing more scattered radiation
Solution Approach 1:
The stop apparatus is made dynamically adjustable with multiple stops that can be positioned at different longitudinal locations along the beam path. This allows the system to adapt the stop size and position dynamically based on the focal spot size and imaging requirements, resolving the contradiction between achieving homogeneous illumination and minimizing scattered radiation.
Solution Approach 2:
The system changes the parameter of stop position (longitudinal location) and stop size by providing multiple stops at different positions. By selecting appropriate stops based on focal spot size, the system optimizes the balance between illumination homogeneity and scattered radiation reduction.
2Object-affected harmful factors
If the stop is positioned closer to the focal spot, then the used ray angle is reduced minimizing scattered radiation, but unsharpness in the detector plane increases
Solution Approach 1:
The system provides dynamic positioning capability with multiple stops at different longitudinal locations, allowing optimal positioning to be selected based on the specific imaging conditions and focal spot size, thereby resolving the contradiction between minimizing scattered radiation and maintaining image sharpness.
Solution Approach 2:
By changing the parameter of stop position (selecting from multiple predetermined positions), the system optimizes the balance between reducing scattered radiation and maintaining acceptable unsharpness levels for the given focal spot size.
3Adaptability or versatility
If multiple independent actuators are used for multi-leaf collimators, then individual recording conditions can be adapted, but device complexity increases
Solution Approach 1:
The patent merges multiple stop functions into a single integrated apparatus with a common support structure. Multiple stops are positioned at different longitudinal locations and can be selectively brought into the beam path, providing adaptability without requiring independent actuators for each stop, thus reducing device complexity.
Solution Approach 2:
The stop apparatus provides multi-functionality by being able to position different stops (with different sizes and positions) to adapt to various recording conditions and focal spot sizes, replacing the need for complex multi-leaf collimator systems with numerous independent actuators.
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 solution effectively minimizes unsharpness and scattered radiation, enhancing image quality by allowing precise adjustment of the stop position and size based on the focal spot size and power of the X-ray source, ensuring homogeneous illumination and reduced noise in CT scanner images.
Implementation Method 1
scattered radiation can be reduced if the computed tomography system is designed and/or operated such that only a limited, relevant solid angle range is illuminated with X-rays
Implementation Method 2
a stop size, i.e., an aperture of the stop, which defines the used ray angle is selected to have a size such that the sensor surface of the detector is completely illuminated
Data Source
AI summary
A variable stop apparatus for arrangement between an X-ray source and an object to be measured in a CT-scanner and a CT-scanner including the variable stop apparatus are provided. The variable stop apparatus includes a stop carrier that is pivotable about a pivot axis. The stop carrier has at least two stops. The at least two stops are in each case configured to be brought into a predetermined angular position by pivoting the stop carrier. The at least two stops are arranged at different longitudinal positions with respect to a longitudinal direction that is defined by the pivot axis.