TOF PET Attenuation Map Reconstruction Using Tracer Amount

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for estimating attenuation maps in positron emission tomography (PET) imaging, especially in time-of-flight (TOF) PET, face challenges in accurately determining the absolute attenuation sinogram without external data, leading to artifacts and inaccuracies due to unknown constant shifts in the gradient of the attenuation sinogram.

Innovation Solution

The method utilizes the total amount of injected tracer as prior information to determine the constant shift in the attenuation sinogram, allowing for accurate estimation of the attenuation sinogram and correction map solely from TOF PET data, eliminating the need for additional knowledge or external data sources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If non-transmission methods are used to estimate attenuation map without separate transmission scan, then scan time is reduced and patient burden is decreased, but cross-talk artifacts appear in the reconstructed images

Engineering Contradiction:

Improvescan timeVSAvoidimage quality

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The method uses iterative reconstruction where the estimated attenuation map is continuously refined by comparing reconstructed images against the original projection data and adjusting the attenuation estimate accordingly. This feedback loop eliminates cross-talk artifacts while maintaining the advantage of not requiring a separate transmission scan.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The attenuation map estimation is performed dynamically during the image reconstruction process rather than as a static preliminary step. The attenuation coefficients are updated iteratively based on the reconstructed activity distribution, allowing the system to adapt and resolve artifacts in real-time.

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If transmission methods using CT are used for attenuation correction, then attenuation map accuracy is improved, but mismatches between CT and PET energy ranges cause substantial artifacts

Engineering Contradiction:

Improveattenuation map accuracyVSAvoidimage quality

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The method replaces the physical CT scanning mechanism with a computational approach that derives attenuation information directly from PET data. By substituting the mechanical CT system with an algorithmic solution based on TOF PET measurements and consistency conditions, the energy mismatch problem is eliminated while maintaining attenuation correction accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The method transforms the attenuation estimation problem by changing the parameter space from direct CT-based linear attenuation coefficients at 60-80 keV to derived attenuation coefficients at 511 keV using PET data. This parameter transformation eliminates the energy-dependent mismatch between CT and PET while preserving the essential attenuation information needed for accurate quantification.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If attenuation map is estimated using gradient of attenuation sinogram, then computation is simplified, but unknown constant shift leads to inaccurate attenuation correction

Engineering Contradiction:

Improvecomputation simplicityVSAvoidattenuation sinogram accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The method performs preliminary action by incorporating the constraint of known total tracer amount into the attenuation estimation process before final reconstruction. By using this prior information to determine the integration constant, the method maintains computational simplicity while ensuring accuracy in the attenuation sinogram estimation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The total tracer amount serves as an intermediary constraint that connects the gradient-based attenuation estimation to the absolute attenuation values. This intermediary parameter allows the method to bridge the gap between the simplified gradient computation and the accurate absolute attenuation correction without requiring complex additional measurements.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10537299B2Attenuation map reconstruction from TOF PET data

Publication Date: 2020.01.21 RENESSELAER POLYTECHNIC INST

AI summary

Systems and methods for determining an attenuation sinogram for a time-of-flight (TOF) positron emission tomography (PET) scan using only TOF PET data, and including use of the total amount of tracer provided to the subject of the TOF PET scan, are provided. The total amount of injected tracer can be used to determine the otherwise unknown constant shift present when an attenuation sinogram is estimated using the gradient of the attenuation sinogram. The attenuation sinogram can therefore be accurately and stably determined without any additional knowledge on the attenuation sinogram or map.