Non-Ionizing Optical Attenuation Map Generation for Emission Tomography
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Solution Overview
Problem
In emission tomography, the lack of an attenuation map leads to artefacts in image reconstruction, making interpretations challenging, especially when CT or MR systems are not available, or when they impose additional radiation dose or have limited fields of view, resulting in truncation artefacts.
Innovation Solution
An imaging apparatus that uses non-ionizing radiation from secondary imaging systems, such as visual or range-finding devices, to generate a volumetric attenuation map, allowing for attenuation-corrected image reconstruction using projection data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CT scan is used to obtain attenuation map, then attenuation correction is improved, but radiation dose increases
Solution Approach 1:
The patent introduces an optical imaging system as an intermediary to capture surface images of the object. These surface images serve as a mediator between the emission tomography system and the attenuation map generation, enabling attenuation correction without direct CT scanning. The optical system captures geometric information that is then used to construct a simplified attenuation map, thereby reducing radiation exposure while maintaining correction accuracy.
Solution Approach 2:
The patent creates a simplified geometric model (copy) of the object based on optical surface images rather than using full CT scan data. This copy includes essential geometric features needed for attenuation correction but omits detailed internal structures, thereby reducing the radiation dose required while maintaining sufficient accuracy for emission tomography reconstruction.
2Measurement precision
If CT scan is used to obtain attenuation map, then attenuation correction is improved, but device complexity increases
Solution Approach 1:
The patent makes the optical imaging system multi-functional by using it for both surface visualization and attenuation map generation. The same optical camera system that captures images for display purposes is also utilized to extract geometric information for attenuation correction, eliminating the need for a separate dedicated system and thereby reducing overall device complexity.
Solution Approach 2:
The patent extracts only the essential geometric information needed for attenuation correction from the optical surface images, rather than requiring complete CT scan data. This extraction approach simplifies the system requirements by focusing only on the minimum necessary information (surface geometry and estimated thickness) needed to generate a functional attenuation map.
3Device complexity
If CT field of view is limited, then device complexity is reduced, but truncation artefacts increase
Solution Approach 1:
The patent transitions from requiring 3D volumetric CT data to using 2D surface images for attenuation map generation. By working with 2D optical images and estimating thickness in the third dimension through computational methods, the system achieves attenuation correction without needing a large CT field of view, thereby avoiding truncation artifacts while maintaining system simplicity.
Solution Approach 2:
The patent performs preliminary estimation of object thickness and attenuation properties based on optical surface images before the emission tomography reconstruction. This preliminary action provides sufficient attenuation information to reduce or eliminate truncation artifacts in the final reconstruction, without requiring complete CT coverage of the entire object volume.
Data Source
AI summary
A method of imaging includes obtaining projection data for an object representing an intensity of radiation detected along a plurality of rays through the object, obtaining an outline of the object via a secondary imaging system, the secondary imaging system using non-ionizing radiation, determining, based on the outline, a model and model parameters for the object, calculating, based on the model and the model parameters, a volumetric attenuation map for the object, and reconstructing, based on the projection data and the volumetric attenuation map, an attenuation-corrected volumetric image.