PET Attenuation Map Estimation Using Scattered Coincidence Events
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Solution Overview
Problem
Standalone PET systems face challenges in attenuation correction without CT scans, particularly in distinguishing between activity and attenuation, leading to ambiguities in image reconstruction due to self-cross-talk and cross-talk issues, especially with scattered photons being discarded.
Innovation Solution
A method and system that utilize scattered events to estimate attenuation maps, incorporating algorithms like MLAA and MLEM, and generate activity and attenuation map pairs, resolving ambiguities by computing Compton angles and likelihoods of scatter points, and filtering backprojection techniques to correct for attenuation self-cross-talk and cross-talk between activity and attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scattered photons are excluded from processing, then measurement precision is improved by reducing noise, but loss of information occurs as useful attenuation data is discarded
Solution Approach 1:
The patent converts scattered photons, traditionally considered harmful noise to be excluded, into beneficial information sources for estimating attenuation maps. By processing scattered events and applying deconvolution techniques, the system transforms what was discarded waste data into useful attenuation correction information, resolving the contradiction between precision and information loss.
2Device complexity
If standalone PET systems are used without CT, then device complexity is reduced, but measurement precision deteriorates due to inability to distinguish activity from attenuation
Solution Approach 1:
The patent enables the PET system to perform its own attenuation correction using only its detected scattered photon data, without requiring external CT equipment. The system serves its own attenuation correction needs by processing its own scattered events through deconvolution and MLAA algorithms, eliminating the need for additional CT hardware while maintaining precision.
3Loss of information
If scattered events are included in reconstruction, then loss of information is reduced, but measurement precision may worsen due to uncertainty in true trajectory
Solution Approach 1:
The patent extracts and separates scattered photon information from the total detected events, processing it through specialized deconvolution algorithms before integration into the final reconstruction. This extraction approach allows the system to utilize scattered event information for attenuation correction while isolating the trajectory uncertainty effects, preventing them from degrading overall precision.
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 allows for accurate attenuation correction in standalone PET systems using existing hardware, improving image reconstruction by distinguishing between activity and attenuation, and resolving ambiguities in image reconstruction, enhancing the accuracy of metabolic activity imaging.
Implementation Method 1
Some emitted photons are deflected or Compton scattered. As photons are scattered, the photons lose energy based on the angle of deflection.
Data Source
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AI summary
An imaging system (36)includes a Positron Emission Tomography(PET) scanner (38) and one or more processors (52). The Positron Emission Tomography (PET) scanner (38)which generates event data including true coincident events and scatter events, the event data includes each end point of a line of response (LOR) and an energy of each end point. The one or more processors (52)are programmed to generate (72)a plurality of activity map and attenuation map pairs based on the true coincident events, and select (76)an activity map and an attenuation map from the plurality of activity and attenuation map pairs based on the scattered events.