Respiratory Motion Extraction from CT Projection Data
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Solution Overview
Problem
Current medical imaging systems, such as those used in radiation therapy planning, rely on external sensors to track respiratory motion, which complicates patient setup, is expensive, and may not accurately capture internal tissue movement during image acquisition.
Innovation Solution
A method and apparatus that analyze projection data to extract timing information by tracking the center of mass of the tissue, allowing for the synchronization of CT images with the motion of the tissue, thereby reducing motion-related artifacts and eliminating the need for external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external sensors are used to track respiratory motion, then respiratory activity can be monitored, but patient setup complexity increases and cost increases
Solution Approach 1:
The imaging system itself serves as the sensing mechanism by analyzing projection data to extract respiratory motion information. The system uses its own acquired imaging data to track center of mass changes and determine respiratory phase, eliminating the need for separate external sensing devices and simplifying patient setup
Solution Approach 2:
The projection data acquisition system performs multiple functions: it captures both the anatomical imaging data needed for diagnosis/treatment planning and simultaneously extracts respiratory motion information. This multi-functionality eliminates the need for dedicated respiratory monitoring equipment
2Measurement precision
If external sensors are placed on the patient's chest, then respiratory waveform can be obtained, but the system becomes expensive
Solution Approach 1:
The imaging system extracts respiratory waveform information from its own projection data without requiring external sensing equipment. By analyzing center of mass changes in the acquired projection data, the system generates respiratory waveforms using only its existing hardware, significantly reducing system cost
Solution Approach 2:
Instead of using physical external sensors on the patient, the system creates a virtual respiratory signal by processing and analyzing the projection data. The center of mass trajectory extracted from imaging data serves as a surrogate for physical sensor measurements
3Measurement precision
If external sensors are used for respiratory gating, then respiratory phase can be tracked, but preparation time increases
Solution Approach 1:
The system immediately begins extracting respiratory phase information from projection data as soon as imaging starts, without requiring separate sensor placement and calibration steps. The respiratory gating signal is generated concurrently with image acquisition, eliminating preparation delays
Solution Approach 2:
The respiratory motion extraction is performed continuously throughout the imaging process using the acquired projection data, so respiratory phase information is available from the start of scanning without requiring preliminary sensor setup or separate calibration procedures
4Ease of operation
If external sensors track chest wall motion, then respiratory activity is monitored, but internal tissue motion may not be accurately captured
Solution Approach 1:
The system analyzes projection data specifically from regions corresponding to internal tissues and organs of interest, rather than relying on external chest wall markers. By extracting center of mass changes from the actual tissue being imaged, the system directly captures internal tissue motion characteristics
Solution Approach 2:
The system creates a direct measurement of internal tissue motion by processing the projection data that passes through the tissue itself. The center of mass trajectory derived from attenuation patterns in the projection data represents actual internal tissue position rather than external surrogate markers
Data Source
AI summary
The present technique provides a novel method and apparatus for determining the motion of an internal tissue or organ undergoing dynamic movement such as a respiratory cycle. Particularly, the technique provides for a method and system for processing projection data to determine the motion rather than relying on additional data acquired from an external sensor. The motion is extracted from projection data by tracking the change over time in projections from the same projection angle and/or conjugate projection angle pairs. The extraction is possible because multiple gantry rotations occur in the time period of a single respiratory period. The motion information may in turn be used to facilitate data acquisition or image reconstruction, such as by gating techniques, to reduce or eliminate motion related artifacts.