Average CT Attenuation Correction for PET/CT Misalignment
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Solution Overview
Problem
The mismatch in temporal and spatial resolutions between CT and PET scans in PET/CT and SPECT/CT imaging leads to misalignment and inaccurate quantification of tumors, particularly in the thorax and abdomen, due to differences in breathing states during CT and PET data acquisition.
Innovation Solution
The use of average CT (ACT) data from 4D-CT imaging, which averages multiple phases of respiratory and cardiac cycles to match the temporal resolution of PET data, improving tumor quantification and localization without requiring additional hardware or respiratory monitoring devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If CT scan is performed with high temporal resolution (less than 1 second), then CT image quality is improved, but mismatch with PET temporal resolution (many breathing cycles) causes misalignment artifacts
Solution Approach 1:
The patent applies preliminary action by acquiring multiple CT phases throughout the PET acquisition period and preparing them in advance. These pre-acquired CT phases are then selected or combined based on the actual PET data temporal characteristics, ensuring the attenuation map matches the PET temporal resolution before reconstruction occurs.
Solution Approach 2:
The patent implements dynamics by making the CT temporal resolution adaptive rather than fixed. The system dynamically selects or combines CT phases based on the PET acquisition duration and breathing patterns, transforming the static high-resolution CT into a dynamic attenuation map that matches the temporal characteristics of the PET data.
2Reliability
If CT scan duration is extended to match PET temporal resolution, then alignment accuracy is improved, but scan time increases reducing productivity
Solution Approach 1:
The patent applies segmentation by dividing the CT acquisition into multiple discrete phases distributed throughout the PET scan duration. Instead of acquiring all CT data continuously before or after PET, the CT scan is segmented into multiple shorter acquisitions that collectively cover the entire PET temporal range, improving alignment without requiring a single extended scan.
Solution Approach 2:
The patent implements periodic action by acquiring CT phases at regular intervals during the PET acquisition. This periodic sampling of CT data throughout the PET scan ensures temporal correspondence while maintaining efficient scan throughput, as the CT scanner operates in periodic bursts rather than continuous or extended single-phase mode.
3Measurement precision
If 4D-CT is used to account for respiratory motion, then tumor localization accuracy is improved, but device complexity and radiation dose increase
Solution Approach 1:
The patent applies self-service by utilizing the PET scanner's existing temporal sampling capability to drive the CT phase selection. The PET acquisition timeline itself serves as the reference for determining which CT phases are needed, eliminating the requirement for separate respiratory monitoring systems or external gating devices. The system serves itself using its own operational parameters.
Solution Approach 2:
The patent implements universality by making the CT phases serve multiple functions: they provide both anatomical reference information and temporal correspondence with PET. The same set of CT phases acquired during the PET scan serves dual purposes, eliminating the need for separate 4D-CT respiratory monitoring infrastructure while achieving similar alignment accuracy.
Data Source
AI summary
Embodiments of the present invention provide the use of average CT (ACT) to match the temporal resolution of CT and PET to enhance PET imaging and evaluated tumor quantification with HCT and ACT. For example, an embodiment of a method of enhanced PET imaging on a PET/CT scanner includes generating an average CT scan responsive to 4D CT emission image data to thereby correct attenuation in PET emission image data. Another embodiment of a method of attenuation correction in a PET/CT scan includes averaging a plurality of consecutive low dose CT images of approximately one breathing cycle to thereby obtain an average CT.