Multi-Modality Imaging Alignment Using Shared Radiopaque Markers
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Solution Overview
Problem
Multi-modality imaging systems face challenges in aligning CT and PET components due to misregistration of coordinate systems, leading to increased costs and time consumption in the alignment process, particularly when relying on attenuation data methods.
Innovation Solution
A method involving imaging target objects with both CT and PET modalities to generate transmission and emission image data sets, determining target object locations, calculating positional alignment vectors, and using these vectors to align the imaging system, thereby facilitating mechanical or software adjustments for precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If attenuation data methods are used to align CT and PET components, then alignment accuracy is improved, but alignment time and system cost increase
Solution Approach 1:
The alignment process is segmented into two independent parts: (1) CT-to-table alignment using CT imaging of alignment objects with radiopaque markers, and (2) PET-to-table alignment using PET imaging of the same alignment objects. This segmentation allows each modality to be aligned independently and simultaneously, eliminating the sequential dependency that causes time delays while maintaining the accuracy benefits of modality-specific alignment methods.
Solution Approach 2:
A shared alignment object with radiopaque markers serves as an intermediary between CT and PET systems. The same physical object is imaged by both modalities, providing common reference points that enable accurate alignment for each modality without requiring direct interaction between the CT and PET systems during the alignment process.
2Measurement precision
If attenuation data methods are used to align CT and PET components, then alignment accuracy is improved, but system cost increases
Solution Approach 1:
The alignment object serves multiple functions simultaneously: it provides alignment references for both CT and PET modalities, and its radiopaque markers are visible in both CT and PET images. This multi-functionality eliminates the need for separate alignment objects or additional specialized equipment for each modality, reducing system cost while maintaining alignment accuracy.
Solution Approach 2:
The alignment system uses the existing CT and PET imaging capabilities to perform alignment without requiring additional dedicated alignment equipment. The CT and PET systems serve themselves by imaging the shared alignment object, eliminating the need for separate alignment devices and reducing overall system complexity and cost.
3Ease of operation
If inherent registration is assumed between CT and PET images, then processing is simplified, but misregistration errors occur due to coordinate system misalignment
Solution Approach 1:
Alignment is performed as a preliminary action before actual patient imaging. The CT and PET systems are aligned using alignment objects and calculated transformation parameters in advance, so that when patient images are acquired and fused, the coordinate systems are already matched. This eliminates the need for complex real-time registration processing while ensuring accurate image fusion.
Solution Approach 2:
The system uses feedback from the alignment object imaging to calculate transformation parameters that correct coordinate system misalignment. By imaging the known alignment object with both modalities and comparing the results, the system generates feedback information about the misalignment, which is then used to compute correction transformations that improve image registration accuracy.
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 approach reduces alignment time and costs by accurately determining and correcting misalignments between CT and PET systems, enhancing the efficiency and accuracy of image registration without the need for extensive attenuation data processing.
Implementation Method 1
the attenuation object is irradiated with an x-ray beam. An electrical signal that represents the intensity of the impinging x-ray beam and attenuation of the x-ray beam is received at a detector
Implementation Method 2
a radiopharmaceutical is typically employed in tandem with a PET camera to acquire PET data
Implementation Method 3
PET imaging system is modified to generate attenuation data
Data Source
AI summary
A method of determining component misalignment in a multi-modality imaging system includes imaging a plurality of target objects with a first modality unit to generate a tomographic image data set and imaging the plurality of targets with a second modality unit to generate an emission image data set. The method also includes determining a location of the target objects in the emission image data set to produce emission target object location coordinates, calculating a positional alignment vector for each target object based on the emission target object location coordinates, and aligning the multi-modality imaging system based on the positional alignment vectors.