Variable-Speed Gantry CT Scanning for Respiratory Motion Artifacts
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Solution Overview
Problem
Computed tomography scanning of moving anatomical structures, such as the lungs during respiration, results in motion artifacts due to the changing shape and position of the structure, degrading the accuracy of tomograms and requiring complex algorithms or patient-breathing adjustments to mitigate these issues.
Innovation Solution
Adjusting the speed of the gantry during scanning, synchronized with the patient's respiratory signal, to optimize the sampling rate and minimize motion artifacts, allowing for accurate tomogram reconstruction without the need for artificial breathing patterns or prolonged scanning times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gantry scans at constant speed, then the scanning process is simple and fast, but motion artifacts are introduced when scanning moving anatomical structures
Solution Approach 1:
The gantry scanning speed is made dynamic rather than constant. The system adjusts the gantry speed in real-time based on the respiratory phase, slowing down during end-inspiration and end-expiration when the lungs are relatively stationary, and speeding up during transition phases. This dynamic speed adjustment allows the system to capture high-quality projections during stable respiratory phases while maintaining overall scanning efficiency.
Solution Approach 2:
The system incorporates feedback from respiratory monitoring to control the gantry speed. A respiratory signal is continuously monitored and fed back to the gantry control system, which automatically adjusts the scanning speed according to the detected respiratory phase. This closed-loop feedback mechanism ensures that projections are acquired at optimal moments without requiring manual intervention or complex patient instructions.
2Measurement precision
If the gantry slows down to capture projections during stable respiratory phases, then motion artifacts are reduced, but scanning time increases
Solution Approach 1:
The system exploits the periodic nature of respiration to optimize scanning. Instead of maintaining a constant slow speed throughout the scan, the gantry periodically adjusts its speed to match the respiratory cycle. During each respiratory cycle, the gantry slows down only during the brief periods at end-inspiration and end-expiration when stable projections can be captured, then speeds up during the transition phases. This periodic speed modulation captures necessary projections while minimizing total scanning time.
Solution Approach 2:
The system applies speed reduction only partially, specifically during the critical phases when stable projections are needed, rather than maintaining reduced speed throughout the entire scan. By applying the speed adjustment only during end-inspiration and end-expiration windows (typically 10-20% of the total scan time), the system achieves motion artifact reduction without proportionally increasing total scanning duration.
3Measurement precision
If gated scanning is used to reject projections during movement, then motion artifacts are reduced, but the number of usable projections decreases
Solution Approach 1:
Instead of acquiring all projections at constant speed and then rejecting those taken during motion (post-acquisition gating), the system performs preliminary action by pre-synchronizing the gantry speed with the respiratory phase before projection acquisition. The gantry is slowed down in advance during end-inspiration and end-expiration phases, ensuring that high-quality projections are captured during stable periods. This proactive approach maximizes the number of usable projections from the outset.
Solution Approach 2:
The system converts what would traditionally be considered wasted scanning time (when the gantry is slowed down) into a benefit by capturing high-quality projections during stable respiratory phases. The speed reduction, which might seem to decrease productivity, actually increases the proportion of usable projections by ensuring they are taken during motion-minimal phases, thereby improving overall data quality without requiring aggressive rejection of projections.
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 reduces motion artifacts and allows for more accurate tomographic imaging of moving structures, such as lungs, while enabling patients to breathe naturally during scans, thereby improving diagnostic accuracy and reducing radiation exposure.
Implementation Method 1
the scanning source sends some form of detectable penetrating signal through the patient's body, and the resultant signal that is detected by the scanning detector provides information
Data Source
AI summary
In one embodiment of the invention, a method for obtaining a tomogram of an anatomical structure is disclosed. In one step, an anatomical structure is scanned using a scanning source and a scanning detector. Both the scanning source and detector are connected to a gantry. In another step, the speed of the gantry is altered during the scanning process. Additionally or optionally the frame rate of the scan can be modified in such step. In a particular embodiment of the invention, the speed of the gantry is altered in synchronicity with the respiratory signal of a patient. Using such a method, a tomogram of an anatomical structure is obtained.