Cone Beam CT Extremity Scanner with Independent Source and Detector Arcs
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Solution Overview
Problem
Conventional cone beam computed tomography (CBCT) systems face challenges in imaging extremities like knees and ankles due to limited angular rotation, poor image quality, and patient discomfort, as well as the need for adaptable and ergonomic solutions to accommodate different patient positions and load-bearing conditions.
Innovation Solution
A CBCT apparatus with a support structure and scanner assembly that allows independent movement of the radiation source and detector, providing a gap for radial access and enabling both CBCT and tomography imaging modes, with a control panel for operator input, and radiation shielding to ensure patient safety and comfort during imaging.
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 the paired extremity blocks the radiation source and detector from accessing certain angles
Solution Approach 1:
The system divides the imaging task into two separate movable components: the radiation source travels along an outer arc path while the detector travels along an inner arc path. This segmentation allows each component to independently navigate around obstacles, with the source taking an outer route and the detector taking an inner route through the gap between the paired extremities.
Solution Approach 2:
The system transitions from a conventional single-orbit path to a two-dimensional coordinated motion system where the source and detector move along different radial distances from the scan volume center. The source follows an outer arc at radius R2 while the detector follows an inner arc at radius R1, creating a layered orbital structure that bypasses physical obstructions.
2Measurement precision
If the detector is positioned close to the subject and the source at a sufficient distance for optimal image quality, then image quality improves, but radiation levels at the patient position become considerably higher
Solution Approach 1:
The system dynamically adjusts the radial positions of both the radiation source and detector along their respective arc paths. The source can vary its distance from the scan volume center along the outer arc, and the detector can vary its distance along the inner arc, allowing real-time optimization of the source-to-detector geometry to balance image quality requirements against radiation exposure levels.
3Productivity
If the patient is required to assume an awkward or uncomfortable position for CBCT imaging, then images can be obtained, but the joint may be under excessive strain or insufficient strain, failing to represent normal movement or posture conditions
Solution Approach 1:
The system creates a universal imaging configuration that can accommodate multiple patient positions and extremity orientations. By providing a gap in both the source and detector paths, the system can image the same type of joint (e.g., knee) in different positions - weight-bearing, non-weight-bearing, flexed, extended - without requiring the patient to assume awkward postures, thereby enabling multi-functional imaging capability.
4Device complexity
If the radiation source and detector follow the same circular scan path, then the system structure is simple, but the paired extremity blocks access to certain imaging angles
Solution Approach 1:
The system segments the single scan path into two distinct concentric arc paths: an outer arc for the radiation source and an inner arc for the detector. This segmentation allows the source to traverse angles that would be blocked by paired extremities while the detector navigates through the gap between them, collectively achieving complete circumferential coverage.
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 solution allows for improved image quality and patient accessibility, enabling CBCT imaging of extremities under normal load-bearing conditions with reduced radiation exposure and enhanced ergonomic positioning, accommodating various patient postures and imaging modes.
Implementation Method 1
a radiation source, the source configured to move along at least a portion of a source path outside the detector path
Data Source
Figure 1
Figure 2~3A
Figure 3B
AI summary
An apparatus for cone beam computed tomography can include a support structure, a scanner assembly coupled to the support structure for controlled movement in at least x, y and z orientations, the scanner assembly can include a DR detector configured to move along at least a portion of a detector path that extends at least partially around a scan volume with a distance D1 that is sufficiently long to allow the scan volume to be positioned within the detector path; a radiation source configured to move along at least a portion of a source path outside the detector path, the source path having a distance D2 greater than the distance D1, the distance D2 being sufficiently long to allow adequate radiation exposure of the scan volume for an image capture by the detector; and a first gap in the detector path.