Respiratory Motion Compensation in Cardiac CT Angiography
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Solution Overview
Problem
Current CT coronary artery angiography techniques struggle to account for respiratory motion during data acquisition, leading to incomplete data sets and the need for repeated procedures, especially in patients who cannot hold their breath.
Innovation Solution
The method generates data sets corresponding to sub-volumes over multiple cardiac cycles, selects sub-volume data sets in a common cardiac phase, calculates respiratory motion vectors based on characteristic points, and reconstructs images to compensate for respiratory motion, allowing for complete data sets in both cardiac and respiratory phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the patient holds their breath during data acquisition, then complete data sets can be obtained in a common respiratory phase, but the technique fails when patients cannot or do not hold their breath
Solution Approach 1:
The patent extracts respiratory motion information from the acquired data by identifying characteristic points and calculating motion vectors, separating the respiratory compensation function from the breath-holding requirement. This allows the system to obtain complete data sets without requiring patients to hold their breath.
Solution Approach 2:
The patent applies asymmetric treatment to different regions of the data set by generating respiratory motion compensation specifically for sub-volumes where motion is detected, while maintaining standard processing for other regions. This targeted approach compensates for respiratory motion without requiring global breath holding.
2Measurement precision
If cardiac and respiratory gating are both applied to the data, then motion correction is achieved, but significant sections of data along the coronary artery are lost
Solution Approach 1:
The patent applies local quality by calculating respiratory motion compensation specifically for sub-volumes where respiratory motion is detected, rather than uniformly processing the entire data set. This localized approach corrects motion artifacts in affected regions while preserving data integrity in regions without significant motion.
Solution Approach 2:
The patent uses partial action by applying respiratory motion compensation to only those sub-volumes that exhibit significant respiratory motion, determined by comparing characteristic points across cardiac phases. This selective compensation avoids the excessive data loss that would result from applying rigid gating to the entire data set.
3Reliability
If the data acquisition period is extended to accommodate patients who cannot hold their breath, then more complete data can be obtained, but contrast agent dose limits are exceeded
Solution Approach 1:
The patent converts the harmful effect of respiratory motion during data acquisition into a beneficial feature by using characteristic point tracking to calculate motion vectors. These vectors are then used to compensate for respiratory motion, allowing complete data sets to be obtained without extending the acquisition period and exceeding contrast agent dose limits.
4Loss of information
If a low pitch is used during CT scanning, then sufficient redundant data is generated for retrospective gating, but the scanning time is extended
Solution Approach 1:
The patent performs preliminary action by generating respiratory motion compensation data during the initial data acquisition phase using characteristic point tracking. This pre-computed motion information is then applied during image reconstruction, eliminating the need for extended scanning times that would result from using lower pitch values to generate redundant data.
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A CT angiography apparatus (10) compensates for respiratory motion. During a helical scan, a radiation source (16) and a detector (18) generate data sets corresponding to a plurality of sub- volumes of a blood vessel over a plurality of cardiac cycles. Sub- volume data sets corresponding to a selected cardiac phase are reconstructed (40) into a plurality of sub- volume images (54'1, 54'2, 54'3). Characteristic points (561, 562, 563) in the sub-volume images are identified. A computer routine or processor (48) calculates a respiratory motion vector based on the identified characteristic points in a plurality of the sub-volume images. An image reconstruction routine or processor (50) reconstructs the original sub-volume data (36) in the selected cardiac phase into a volume image representation (50') using the calculated respiratory motion vector.