Wide-Coverage Axial CT Planning with Gradient-Based Range Limits
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Solution Overview
Problem
Wide-detector CT systems suffer from cone-beam geometry-related artefacts, particularly near the edges of the detector, which cannot be fully compensated by processing alone, leading to reduced signal quality and increased radiation dose.
Innovation Solution
A method and device for planning an axial image acquisition using a pre-scan image to select scan range limits based on image gradient thresholds, adjusting these limits to avoid strong gradients, and applying a second-pass reconstruction algorithm to correct artefacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wide-detector CT systems are used to cover large longitudinal ranges, then image acquisition time is reduced and patient movement is minimized, but cone-beam geometry-related artefacts increase near the detector edges
Solution Approach 1:
The system performs a pre-scan to acquire preliminary image data before the actual diagnostic scan. This preliminary data is used to identify strong image gradients and adjust the scan range limits to avoid positioning them at the detector edges, thereby preventing cone-beam artefacts while maintaining the efficiency of wide-coverage imaging
2Area of stationary object
If scan range limits are extended to cover the entire detector range, then coverage is maximized, but signal quality deteriorates near the edges due to insufficient data for exact reconstruction
Solution Approach 1:
The system applies different quality standards to different regions of the scan range. By analyzing image gradients in the pre-scan data, the system identifies regions with strong gradients near the edges and adjusts the scan range limits locally to ensure sufficient data coverage for exact reconstruction, while maintaining maximum coverage in regions where signal quality is adequate
3Object-affected harmful factors
If second-pass reconstruction methods are applied to reduce cone-beam artefacts, then artefact reduction is achieved, but the method fails when strong gradients are inside the projected cone but outside the reconstructable region
Solution Approach 1:
The pre-scan is performed as a preliminary action to identify the location of strong image gradients before the actual scan. This allows the system to adjust the scan range limits in advance to ensure that strong gradients are positioned within the reconstructable region, preventing the failure mode of second-pass reconstruction methods
Solution Approach 2:
The system uses feedback from the pre-scan image gradient analysis to adjust the scan range limits for the actual diagnostic scan. This feedback mechanism ensures that the final scan is configured to avoid positioning strong gradients at the edges of the reconstructable region, thereby ensuring reconstruction reliability
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
Ensures high-quality image reconstruction without patient movement, reduces artefacts, and minimizes radiation dose by optimizing scan parameters and applying image processing techniques.
Implementation Method 1
a computed tomography scanner having an X-ray source and a two-dimensional detector array
Implementation Method 2
a second-pass reconstruction algorithm to correct cone-beam geometry-related artefacts
Data Source
AI summary
The present invention relates to a device (10) and related method and computer-program product for planning an acquisition by a CT scanner (20). The device receives a pre-scan image of the object from the scanner via an input (12). A processor (16), in use of the device, obtains a parameter selection based on the pre-scan image, in which this parameter selection comprises at least axial upper and lower scan range limits of a region of the object to be scanned. The processor determines a value indicative of an image gradient or gradient component in the pre-scan image at the upper and/or lower scan range limit or in a predetermined neighborhood thereof. If this value exceeds a threshold, a user is informed via an output (18) that the selected scan range does not satisfy a quality criterium for reconstruction and/or a new parameter selection is determined by repositioning, resizing and/or changing an orientation of the selected region to be scanned.