MLAA Attenuation Map Completion for PET Imaging
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Solution Overview
Problem
Current methods for generating attenuation maps in PET imaging systems face challenges due to the smaller field of view of alternative imaging modalities like CT and MR, leading to truncated images and inaccurate attenuation corrections, especially when there is a lack of correlation with electron density and photon attenuation data.
Innovation Solution
A method using Maximum-Likelihood Expectation Maximization (MLEM) techniques to iteratively improve estimated attenuation coefficients from PET emissions data, combining them with truncated image data to generate a complete and accurate attenuation map, even outside the field of view of the alternative modality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a smaller field of view imaging modality (CT or MR) is used to generate attenuation maps, then the imaging speed and resolution of the attenuation map are improved, but the field of view coverage is reduced leading to truncated images and inaccurate attenuation corrections
Solution Approach 1:
The patent combines PET emissions data with truncated morphological image data (CT or MR) to generate a complete attenuation map. The PET data provides whole-field attenuation information while the morphological images provide anatomical context, merging these complementary data sources to overcome the limited field of view of CT/MR while maintaining their imaging speed and resolution advantages.
Solution Approach 2:
The patent uses PET emissions data as an intermediary to bridge the gap between the truncated morphological images and the complete attenuation map. The PET data serves as a mediator that fills in the missing attenuation information from regions outside the CT/MR field of view, enabling accurate attenuation correction across the entire PET field of view.
2Area of stationary object
If PET emissions data is used to reconstruct the complete attenuation map including missing portions, then the field of view coverage is improved, but the measurement precision and reliability may be reduced due to lower signal quality in truncated regions
Solution Approach 1:
The patent applies different processing strategies to different regions of the image based on data quality. In regions where CT or MR data is available, those high-quality morphological images are used for attenuation correction. In truncated regions where only PET data is available, the PET emissions data is used to estimate attenuation coefficients. This local quality approach ensures optimal precision in each region while maintaining complete field of view coverage.
Data Source
AI summary
The present invention is a method of generating a best estimate of an image attenuation map derived from a truncated image attenuation map and PET emissions data for the object being imaged by a morphological imaging modality. The method involves a plurality of steps beginning with the recordation and processing of PET emissions data. Next, the morphological imaging modality records image data which is processed to determine an attenuation map. The attenuation map, for image modalities such as CT and MR scanning systems integrated with PET, is truncated, resulting in a truncated attenuation map image. Pixels for which attenuation data needs to be determined are identified and attenuation coefficients for these pixels are estimated and combined with the truncated attenuation map to generate a full initial attenuation map for the image, which is iteratively processed together with the PET emission data until the improvement change in the emission image reaches a defined threshold improvement level.