Spherical Bearing Rail Assembly for Extremity CBCT Positioning
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Solution Overview
Problem
Conventional cone beam computed tomography (CBCT) systems face challenges in obtaining complete 360-degree angular rotation for extremity imaging due to physical obstructions from patient anatomy, leading to limited image quality and accessibility issues, especially for extremities like the knee where the radiation source and detector cannot be positioned over the full circular orbit.
Innovation Solution
A radiographic imaging apparatus with elongated rigid guide rails and spherical bearing assemblies allows for gimbaled connections, enabling controlled movement of the radiation source and detector along these rails, facilitating a wider range of angular positions and improved patient access by using a detector transport device with a circumferential access opening that can revolve around the extremity, allowing for imaging beyond the typical 180-degree limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radiation source and detector are positioned to achieve a full 360-degree orbit for CBCT imaging, then complete volumetric data can be obtained, but patient anatomy (paired extremity) blocks the imaging path and prevents positioning over the full circular orbit
Solution Approach 1:
The imaging system is divided into two independent carriages that can operate separately on the guide rails. The first carriage carries the radiation source and the second carriage carries the detector, allowing them to be positioned independently to navigate around anatomical obstructions while still achieving comprehensive angular coverage for volumetric reconstruction
Solution Approach 2:
The system transitions from a single rigid circular orbit to a two-dimensional positioning space along linear guide rails. This allows the source and detector to move independently in multiple positions along the rails, creating alternative imaging paths that bypass anatomical blockages while maintaining the necessary angular range for CBCT reconstruction
2Measurement precision
If the detector is positioned close to the subject and the source is positioned at sufficient distance, then image quality is improved and truncation is reduced, but the range of angular rotation is limited by patient anatomy
Solution Approach 1:
The system employs dynamic positioning of the source and detector along the guide rails rather than fixed positions. This allows the imaging geometry to be adjusted for each angular position to maintain optimal source-to-detector distance and subject coverage, preserving image quality across the available angular range while adapting to anatomical constraints
Solution Approach 2:
The system changes the positioning parameters of the source and detector along the guide rails to optimize imaging geometry at different angles. By adjusting the longitudinal positions of the carriages, the system maintains appropriate source-to-detector distances and minimizes truncation effects across the range of achievable angular rotations
3Device complexity
If conventional fixed-position CBCT systems are used, then the structure is simple, but the system cannot achieve stable movement and versatile positioning for different extremities and imaging conditions
Solution Approach 1:
The dual-carriage system on linear guide rails serves multiple functions: it can position the source and detector at various distances, achieve different angular ranges, accommodate different extremity sizes and positions, and support both load-bearing and non-load-bearing imaging conditions. This universal positioning capability replaces multiple specialized fixed systems with a single adaptable platform
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 configuration enables stable and versatile CBCT imaging for extremities, allowing for adaptable positioning and improved image quality by enabling the source and detector to move around the patient's extremities, even in load-bearing and non-load-bearing conditions, while maintaining patient comfort and safety.
Implementation Method 1
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.
Data Source
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.