CBCT Bearing Rail Assembly for Wider Extremity Scan Rotation
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Solution Overview
Problem
Conventional cone beam computed tomography (CBCT) systems face challenges in obtaining diagnostic-quality 3D images of extremities like the knee due to limited angular rotation of the x-ray source and detector, often obstructed by patient anatomy, and issues with image quality resulting from suboptimal positioning of the radiation source and detector.
Innovation Solution
A radiographic imaging apparatus featuring elongated rigid guide rails with symmetrical shapes and spherical bearing assemblies allows for gimbaled connections, enabling controlled movement of the imaging components to facilitate access and positioning of the extremity, allowing for a wider range of angular rotations and improved image quality by accommodating the patient's anatomy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the x-ray source and detector are positioned to achieve optimal image quality (source at sufficient distance, detector close to subject), then image quality improves, but the angular rotation range is limited due to patient anatomy obstruction
Solution Approach 1:
The patent employs a dynamic positioning system where the detector can be moved along the central axis between the source and subject. This allows the system to adapt its geometry during scanning, enabling optimal image quality at certain angles while maintaining scanning capability at other angles where anatomy would otherwise block the path. The dynamic adjustment resolves the contradiction by making the positioning adaptable rather than fixed.
Solution Approach 2:
The scanning process is divided into multiple segments or stations along the central axis. The detector can be positioned at different locations (first position closer to source, second position closer to subject) depending on the scanning angle. This segmentation allows optimal imaging geometry to be achieved in different angular ranges, effectively overcoming the limitation imposed by patient anatomy.
2Device complexity
If a fixed positioning system is used for the detector, then the system structure is simplified, but the ability to accommodate different patient anatomies and imaging conditions is reduced
Solution Approach 1:
Rather than creating multiple fixed positioning systems, the patent implements a single detector that can dynamically reposition itself along the central axis. This dynamic approach provides the versatility needed to accommodate different patient anatomies while avoiding the complexity of multiple fixed systems. The detector's ability to move between different positions on demand achieves adaptability with relatively simple mechanical means.
3Measurement precision
If the detector is positioned close to the subject for optimal imaging, then image quality improves, but access to certain angular positions is blocked by patient anatomy
Solution Approach 1:
The detector's dynamic positioning capability allows it to be placed in the optimal position (close to subject) only when the imaging geometry permits. When patient anatomy would block access, the detector can be repositioned to an alternative location along the central axis. This dynamic adaptation maintains ease of operation by allowing the system to automatically adjust to accessible positions while still achieving good image quality.
Solution Approach 2:
The imaging process is segmented into different detector positions along the central axis. For certain angular ranges, the detector operates from a first position, while for other angular ranges, it operates from a second position. This segmentation allows the system to access all necessary imaging positions without being blocked by patient anatomy, while maintaining optimal imaging geometry in each segment.
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 apparatus enables stable and versatile CBCT imaging of extremities, allowing for comprehensive 3D imaging under various conditions, including load-bearing and non-load-bearing scenarios, with enhanced patient access and reduced image truncation, thereby improving diagnostic capabilities.
Implementation Method 1
spherical bearing assemblies allows a gimbaled connection thereto
Data Source
Figure 1~2
Figure 3A~3C
Figure 3B
AI summary
A radiographic imaging apparatus includes elongated rigid guide rails having equivalent symmetrical shapes. Carriages attached to the guide rails are configured to move along a length of the guide rails and to support a portion of the imaging apparatus and to facilitate movement thereof along the guide rails. A first type spherical bearing assembly allows a gimbaled connection thereto while allowing substantially no axial movement. A second type spherical bearing assembly allows a gimbaled connection thereto while allowing a limited amount of axial movement. Frame mounts are each attached to one of the first type and second type spherical bearing assemblies to facilitate movement having a one sided tolerance along the guide rails.