Cone-Beam CT Field of View Expansion via Composite Scanning
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Solution Overview
Problem
Conventional Cone-Beam Computerized Tomography (CBCT) systems face limitations in increasing the maximum Field-Of-View (FOV) without modifying the physical components, leading to reduced image quality and incomplete coverage of the region of interest due to radiation distribution issues and patient movement artifacts.
Innovation Solution
A method and apparatus that utilize a composite scanning protocol with multiple partial acquisitions and repositioning steps to stitch together volumes, allowing for a larger reconstructed FOV without altering the X-ray detector or source geometry, minimizing patient movement and registration errors through synchronized mechanical movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the dimensions of X-ray detector, beam aperture angle, or source-to-object distance are increased to enlarge FOV, then the maximum FOV dimension is improved, but the apparatus becomes more costly and its overall dimensions increase
Solution Approach 1:
The patent divides the acquisition process into multiple sequential scanning steps, where the detector is repositioned between scans to capture different regions. This segmentation allows the system to build up a larger FOV composite image using the same physical detector, avoiding the need for a larger detector or more complex apparatus geometry.
Solution Approach 2:
The patent introduces dynamic repositioning of the X-ray detector between scanning steps, allowing the detector to move to different positions relative to the object. This dynamic adjustment enables the system to cover a larger FOV without requiring a physically larger detector or apparatus, resolving the contradiction between FOV size and apparatus complexity.
2Area of stationary object
If multiple sequential acquisitions are performed to increase FOV, then the FOV coverage is improved, but the total acquisition time increases and patient movement artifacts worsen
Solution Approach 1:
The patent performs preliminary positioning of the detector and planning of scan paths before the actual multi-step acquisition begins. This preliminary preparation optimizes the scanning sequence and detector repositioning strategy to minimize total acquisition time while ensuring complete FOV coverage, thereby reducing the window for patient movement artifacts.
Solution Approach 2:
The patent implements continuous scanning protocols where the detector repositioning and data acquisition are coordinated to minimize idle time between steps. By maintaining continuous useful action throughout the multi-step process, the total acquisition time is reduced, limiting the opportunity for patient movement and associated artifacts.
3Area of stationary object
If the detector is offset to expand FOV, then the FOV dimension is improved, but the radiation intensity distribution becomes inhomogeneous requiring additional adjustment steps
Solution Approach 1:
The patent applies local quality adjustment by modifying the radiation intensity distribution specifically in regions affected by detector offset. Through selective compensation techniques applied to different areas of the detector surface, the system maintains uniform image quality across the expanded FOV without requiring global recalibration of the entire system.
Solution Approach 2:
The patent changes operational parameters such as exposure settings and detector positioning angles to compensate for the inhomogeneous radiation distribution caused by offset. By dynamically adjusting these parameters during the scanning process, the system maintains uniform image quality across the expanded field of view.
4Area of stationary object
If composite scanning protocols with repositioning steps are used, then the FOV is enlarged, but the complexity of the scanning protocol and registration process increases
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors detector position and scanning progress, automatically adjusting subsequent scan parameters based on previous step outcomes. This closed-loop control simplifies the overall protocol complexity by providing real-time guidance and automatic correction, reducing the burden on operators while achieving enlarged FOV.
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
Enables the creation of larger reconstructed volumes with reduced acquisition time, minimized motion artifacts, and direct registration of volumes without preprocessing, while maintaining the cost-effectiveness of existing components and improving image quality by maintaining patient comfort and reducing radiation exposure.
Implementation Method 1
an X-ray source projecting a conic X-ray beam through an object to be acquired, a bi-dimensional X-ray detector positioned so as to measure the intensity of radiation after passing through the object
Data Source
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AI summary
Method and apparatus for increasing the Field Of View dimensions in a cone-beam computerized tomography acquisition, comprising the following steps: A. Selecting an acquisition protocol; B. Positioning a patient; C. Performing a first subacquisition step of a first anatomic area of at least two partially overlapping anatomic areas; D. Repositioning the apparatus for the next subacquisition step; E. Performing the at least one next subacquisition step of the at least further anatomic area; F. Generating the volumetric images relating to the subvolumes; G. Reconstructing a single global volumetric image in which the reconstruction occurs through techniques of image registration (stitching) and blending.