Cone Beam CT Extremity Imaging Spiral Scan Path
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Solution Overview
Problem
Conventional cone beam computed tomography (CBCT) systems face challenges in imaging load-bearing extremities like legs and knees due to limited angular rotation, compromised image quality, and patient discomfort, as well as difficulties in simulating normal weight-bearing conditions, leading to suboptimal imaging results and radiation exposure issues.
Innovation Solution
The design of a CBCT apparatus with adjustable orbital paths for the radiation source and detector, allowing for a circumferential gap to accommodate both extremities, enabling the patient to stand comfortably and allowing for normal weight-bearing imaging, with separate radii for the source and detector paths to optimize radiation exposure and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the x-ray source and detector rotate around the patient's extremity to capture volumetric data, then 3-D volume images can be obtained, but the paired extremity blocks the radiation source and detector from positioning over certain scan circumferences
Solution Approach 1:
The patent transitions from a conventional circular scan path to a spiral or helical scan trajectory. The x-ray source and detector move along a spiral path around the extremity, allowing the system to capture data from angles that would otherwise be blocked by the paired extremity. This dimensional change in the scan trajectory enables complete volumetric imaging without physical obstruction.
Solution Approach 2:
The imaging system employs dynamic motion where the x-ray source and detector follow a spiral trajectory rather than a static circular path. The system dynamically adjusts the scan path to accommodate the patient's anatomy, moving the radiation source and detector along a three-dimensional spiral route that avoids blocked regions while maintaining complete coverage of the target extremity.
2Reliability
If the patient stands in normal posture for weight-bearing imaging, then natural load conditions are maintained, but the paired extremity physically obstructs the x-ray source and detector positioning
Solution Approach 1:
The patent implements a spiral scan trajectory that extends into the third dimension, allowing the x-ray source and detector to access angles above and below the level of the paired extremity. This enables the patient to maintain natural standing posture with weight-bearing load while the spiral path circumvents the physical obstruction caused by the other leg or arm.
3Device complexity
If a conventional circular scan path is used, then the system structure is simple, but the paired extremity blocks the scan path preventing full orbital rotation
Solution Approach 1:
The patent transforms the two-dimensional circular scan path into a three-dimensional spiral trajectory. The x-ray source and detector follow this spiral path, which adds the vertical dimension to the scanning motion. This allows the system to maintain relatively simple mechanics while achieving scan accessibility that circumvents obstructions from paired extremities.
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 enhances patient accessibility, maintains image quality, and allows for accurate imaging of load-bearing extremities under normal weight-bearing conditions, improving the usability and diagnostic quality of CBCT scans.
Implementation Method 1
a radiation source; a second device to move the source along at least a portion of a concentric circular source path
Data Source
AI summary
An apparatus for cone beam computed tomography of an extremity has a digital radiation detector and a first device to move the detector along a circular detector path extending so that the detector moves both at least partially around a first extremity of the patient and between the first extremity and a second, adjacent extremity. The detector path has radius R1 sufficient to position the extremity approximately centered in the detector path. There is a radiation source with a second device to move the source along a concentric circular source path having a radius R2 greater than radius R1, radius R2 sufficiently long to allow adequate radiation exposure of the first extremity for an image capture by the detector. A first circumferential gap in the source path allows the second extremity to be positioned in the first circumferential gap during image capture.