Multi-Modality Camera Alignment Using Geometric Phantom Rods
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing multi-modality imaging systems, such as PET/CT, face challenges in accurately aligning images due to imperfect orthogonal and concentric mounting of cameras, requiring complex and costly quality checks.
Innovation Solution
A framework using a phantom with specific geometrically oriented hot and cold rods allows for the determination of misalignment parameters by imaging with both CT and PET cameras, enabling precise alignment without needing additional isotopes and reducing radiation exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex quality checks are performed to ensure proper alignment of cameras, then image alignment precision is improved, but device complexity and cost increase
Solution Approach 1:
The system performs self-alignment by automatically determining misalignment parameters through image processing of the phantom. The computer system automatically processes images from both cameras, calculates misalignment parameters, and generates alignment transformations without requiring manual quality checks or external intervention.
Solution Approach 2:
A digital phantom with known geometric features is used as a reference copy to compare against actual camera images. The phantom contains hot rods and cold rods with precise spatial relationships that serve as a template for determining camera alignment, replacing complex physical alignment tools.
2Measurement precision
If additional isotopes are used for quality checks, then measurement precision is improved, but radiation dose increases
Solution Approach 1:
The phantom is designed to be visible in both CT and PET modalities simultaneously, serving as a universal reference object for both camera types. The hot rods (radioactive) and cold rods (density-based) provide features that can be detected by either modality, eliminating the need for separate isotopes for each camera type.
Solution Approach 2:
The phantom acts as an intermediary object that mediates the alignment measurement between CT and PET cameras. By imaging the same phantom with both cameras, the system indirectly determines relative alignment without requiring direct interaction between the cameras or additional radiation sources.
3Measurement precision
If precise orthogonal and concentric mounting is implemented, then image alignment is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The phantom is prepared in advance with precisely positioned hot rods and cold rods at known locations. This preliminary setup of reference features allows the system to compensate for manufacturing imperfections in camera mounting, as the known geometry of the phantom provides a baseline for calculating misalignment parameters.
Solution Approach 2:
The system determines misalignment parameters (rotation angles, translation distances) that quantify the deviation from perfect alignment. By measuring these parameters and applying corresponding transformation operations, the system dynamically adjusts for manufacturing tolerances rather than requiring perfect initial alignment.
Data Source
AI summary
A framework for aligning images from a multi-modality imaging system. A first image of a phantom positioned on a patient table may be acquired using a first camera of first modality in the multi-modality imaging system. The phantom may include first and second hot rods, as well as first, second and third cold rods. The first and second hot rods are disposed in a plane that is substantially orthogonal to a travel vector of the patient table, while the first and second cold rods are substantially orthogonal to the travel vector, and the third cold rod is substantially parallel to the travel vector. A second image of the phantom may be acquired using a second camera of second modality in the multi-modality imaging system. Misalignment parameters of the first and second cameras may be determined based on the first and second images.