Rotating Cone Beam CT Housing for Weight-Bearing Extremity Imaging
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Solution Overview
Problem
Conventional cone beam computed tomography (CBCT) systems face challenges in imaging extremities like knees, legs, and feet due to limited angular rotation, poor image quality, and increased radiation exposure, especially when trying to capture 3D images of load-bearing joints and anatomically obstructed areas.
Innovation Solution
The development of a CBCT apparatus with adjustable radiation source and detector paths, allowing for different radii and patient positioning that enables full or partial circular orbits, accommodating the patient's anatomy and allowing for imaging while standing or seated, with features like a circumferential gap for access and a gap closure mechanism to ensure proper detector path completion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If the patient is positioned in a non-standard pose to enable CBCT scanning, then the paired extremity obstruction is avoided, but the joint is imaged under abnormal strain conditions that do not reflect normal weight-bearing states
Solution Approach 1:
Instead of moving the patient's body to accommodate the scanner, the scanner housing is rotated about a vertical axis to reposition the source and detector relative to the patient. This inversion allows the patient to remain in a natural standing or sitting position while the imaging equipment moves around them, enabling weight-bearing joint imaging without abnormal positioning.
Solution Approach 2:
The housing is made rotatable about a vertical axis, transforming a static scanning apparatus into a dynamic one. This rotational capability allows the source and detector to be repositioned around the patient's body, providing flexible access to different scan angles while maintaining the patient's natural posture and the joint's normal loading conditions.
2Measurement precision
If the source and detector are positioned close to the patient for imaging, then image quality is improved, but the radiation exposure to the patient increases
Solution Approach 1:
The system utilizes rotation about a vertical axis (adding a rotational dimension) to reposition the source and detector around the patient's body. This allows the source to be positioned at an optimal distance for image quality while the detector remains close to capture detailed projections, and enables radiation shielding of sensitive areas by positioning them away from the direct beam path during rotation.
Solution Approach 2:
The rotational positioning capability allows dynamic adjustment of source-to-patient and detector-to-patient distances. By changing these parameters through rotation, the system can optimize image quality by maintaining appropriate geometric relationships while managing radiation exposure through varied positioning and potential shielding.
3Loss of information
If a full 360 degree orbit is implemented for source and detector, then complete volumetric data is obtained, but the paired extremity blocks the scan path preventing full rotation
Solution Approach 1:
The scanning orbit is segmented into accessible angular ranges rather than requiring a continuous 360-degree rotation. The housing rotates to positions where the source and detector can obtain projections without being blocked by the patient's paired extremity, collecting sufficient data from multiple segments to reconstruct the volume image.
Solution Approach 2:
Instead of requiring a complete 360-degree orbit, the system uses partial orbits that are sufficient for image reconstruction. The housing rotates through angles that provide adequate projection data while avoiding the blocked regions, accepting that not the full circular path is traversed but obtaining enough information for diagnostic quality imaging.
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 improves image quality, reduces radiation exposure, and allows for accurate 3D reconstruction of extremities, including load-bearing joints, by enabling full or partial circular orbits and accommodating the patient's anatomy, thus overcoming the limitations of conventional CBCT systems.
Implementation Method 1
a radiation source; a radiation source transport actuable to move the source along at least a portion of an arcuate source path
Data Source
AI summary
An apparatus for cone beam computed tomography of lower leg portions of a patient has a radiation source and a source transport actuable to move the source along an arcuate source path within a housing, from one side of a circumferential gap to the other and has a radius R2 about a center. A housing is provided for placement of the patient's foot. A digital radiation detector has a detector transport actuable to move the detector along an arcuate detector path within the housing, the detector path having a radius R1 about the center and concentric with the source path, wherein R1 is less than R2, and wherein the detector path extends from one side of the pedestal indent to the other. A gap closure apparatus is movable to a position that continues the detector path across the circumferential gap and encloses the detector path.