Dynamic Beam Limiting for C-Arm Imaging Misalignment
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Solution Overview
Problem
Imaging systems, such as C-arm devices, suffer from distortions and misalignments due to gravitational forces, leading to increased radiation exposure as the beam size must be larger than the image field to compensate for these distortions, resulting in unnecessary radiation dose.
Innovation Solution
An imaging system with a beam limiting unit and control unit that determines and applies correction factors to reposition and orient the image field within the radiated field, allowing the beam size to be reduced, thereby minimizing radiation exposure by centering the image field within the radiated field and resizing the radiated field to match the image field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the beam size is increased to compensate for gravitational distortion and misalignment, then the image field remains within the beam across all orientations, but the radiation dose increases unnecessarily
Solution Approach 1:
The system performs preliminary determination of the C-arm orientation and calculates the gravitational distortion and misalignment effects before image capture. Based on this preliminary analysis, the control unit pre-adjusts the beam size and shape to precisely match the image field boundaries, rather than using a fixed oversized beam. This preliminary action eliminates the need for excessive beam margin while ensuring the image field remains within the beam.
Solution Approach 2:
The beam size and shape are made dynamic rather than static. The beam limiting unit adjusts the beam dimensions in real-time based on the detected C-arm orientation and the calculated distortion/misalignment characteristics. This dynamic adaptation allows the beam to be minimized for each specific orientation while still guaranteeing that the image field is captured within the beam boundaries.
2Reliability
If a fixed beam size larger than the image field is used, then misalignment due to C-arm bending is compensated, but the radiation dose is larger than optimal
Solution Approach 1:
The system changes the beam parameters (size, shape, position) dynamically based on the C-arm orientation. Instead of using a fixed beam size that is always larger than the image field, the control unit calculates the optimal beam parameters for each orientation by considering the gravitational distortion and misalignment characteristics. This parameter adaptation reduces the beam size to the minimum necessary while maintaining reliable coverage of the image field.
Solution Approach 2:
The system incorporates feedback from orientation detection to beam control. The detected C-arm orientation is fed back to the control unit, which then adjusts the beam limiting unit parameters accordingly. This closed-loop feedback ensures that the beam size is optimized for each specific orientation, preventing both under-coverage and excessive radiation dose.
3Object-affected harmful factors
If the beam size is reduced to match the image field exactly, then radiation dose is minimized, but the image field may fall outside the beam due to distortion
Solution Approach 1:
Before reducing the beam size to match the image field, the system performs preliminary calculation of the gravitational distortion and misalignment based on the C-arm orientation. This preliminary action determines the appropriate beam margin needed for each specific orientation, allowing the beam to be reduced to the minimum safe size rather than using a conservative fixed size.
Solution Approach 2:
The beam size is made dynamic and orientation-dependent. Rather than using a static beam size that provides a fixed margin, the beam limiting unit adjusts the beam dimensions dynamically based on the detected orientation and the calculated distortion characteristics. This dynamic adjustment maintains the reliability guarantee while minimizing the radiation dose.
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 reduces the overall radiation dose and beam cross-sectional area, ensuring that only the necessary radiation is used for image capture while maintaining accurate image alignment, thus improving the efficiency and safety of imaging processes.
Implementation Method 1
the beam source may be an X-ray source
Implementation Method 2
the detector unit detects the rays and converts the received photons into an image signal
Implementation Method 3
One possible source of distortion is gravity and the mass of the imaging system components
Implementation Method 4
the force of gravity may deform the C-arm, resulting in a change of the relative position
Data Source
Figure 1~2
Figure 3~5
AI summary
An imaging system (10) comprises a beam source (20), a detector unit (30), a beam limiting unit (40), and a control unit (50). The beam source (20) generates a beam (22) and projects it onto the detector unit (30), thus generating a radiated field (32) being limited by the beam limiting unit (40). The detector unit (30) provides image data as a result of the beam (22). The control unit (50) is configured to provide image data of a desired region of an object (60) by selecting a predetermined image field (34) of the detector unit. The control unit (50) is configured to determine a correction factor for a relative position and/or a relative orientation of the image field (34) with respect to the radiated field based on an orientation of the imaging system and to control the beam limiting unit as to reduce the cross-sectional area of the beam.