CT Scan Parameter Optimization via Dynamic Exposure Control
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Solution Overview
Problem
Current computed tomography (CT) devices face challenges in optimizing scan parameters to achieve optimal image quality while minimizing radiation dose and motion artifacts, particularly in scans involving the chest and abdomen, where too long or too short exposure times can result in poor image quality or excessive motion artifacts.
Innovation Solution
A CT device with an exposure time determination unit and a scan parameter determination unit that calculate object-specific exposure times based on the maximal available tube current and z-dependent tube current by exposure time product profile, optimizing scan parameters such as collimation aperture, rotation time, pitch, dose, time-dependent tube current, and tube voltage to achieve adequate image quality and reduce motion artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exposure time is increased to reduce image noise, then image quality improves, but motion artifacts increase
Solution Approach 1:
The patent implements dynamic adjustment of exposure time and tube current based on real-time scan progress and detected object motion. The system continuously monitors the scan process and adapts parameters mid-scan to optimize image quality while minimizing motion artifacts, transforming static parameter settings into dynamic control.
Solution Approach 2:
The system changes physical parameters (exposure time, tube current) based on measured conditions during scanning. By adjusting these parameters dynamically according to actual scan progress and detected motion, the system resolves the contradiction between needing sufficient exposure for image quality and minimizing exposure duration to reduce motion artifacts.
2Object-affected harmful factors
If exposure time is decreased to reduce motion artifacts, then motion artifacts reduce, but image noise increases
Solution Approach 1:
The system compensates for reduced exposure time by dynamically adjusting tube current and other scan parameters. When exposure time is decreased to minimize motion artifacts, the system increases tube current or adjusts collimation to maintain adequate photon statistics, thereby preventing image noise from deteriorating.
Solution Approach 2:
The patent employs dynamic parameter adjustment where exposure time, tube current, and other parameters are continuously optimized during the scan based on actual conditions. This dynamic control allows the system to use shorter exposure times without sacrificing image quality, as parameters are adapted in real-time to maintain optimal image characteristics.
3Measurement precision
If tube current is increased to improve image quality, then image quality improves, but radiation dose increases
Solution Approach 1:
The patent applies local quality optimization by adjusting tube current and exposure parameters specifically for regions of interest rather than uniformly across the entire scan volume. The system identifies clinically relevant areas and concentrates radiation dose on these regions while reducing or omitting exposure in non-critical areas, thereby improving image quality where needed while minimizing overall radiation dose.
Solution Approach 2:
The system applies partial action by selectively increasing tube current only in specific z-axis regions or angular sectors where diagnostic information is most critical. Rather than uniformly increasing tube current throughout the entire scan, the system applies enhanced exposure only where necessary to answer the clinical question, reducing unnecessary radiation exposure.
4Object-affected harmful factors
If scan speed is increased to reduce motion artifacts, then motion artifacts reduce, but image quality deteriorates
Solution Approach 1:
The patent implements dynamic parameter adjustment where scan speed, exposure time, and tube current are continuously adapted during the scan based on detected motion and clinical requirements. The system can accelerate the scan through regions with minimal motion while maintaining adequate exposure parameters, and slow down or increase exposure in regions requiring higher image quality, resolving the contradiction between scan speed and image quality.
Solution Approach 2:
The scan volume is segmented into different regions with different motion characteristics and diagnostic importance. The system applies different scan speeds and exposure parameters to different segments, allowing faster scanning through low-motion or non-critical regions while maintaining slower speeds and higher exposure in high-motion or diagnostically critical areas.
Data Source
AI summary
The present invention relates to optimizing values for scan parameters for a scan of an object. An object specific exposure time is determined based on a maximal required value of a z-dependent tube current by exposure time product along a z-axis of the object and a maximal available tube current value of a tube used for the scan of the object (140). The maximal available tube current value depends on a tube voltage and maximal electric power of the tube at given focal spot area (110) and the z-dependent tube current by exposure time product profile is based on a dose index value or a pixel noise index value for the scan of the object, the tube voltage, and a z-dependent object size along the z-axis (120). The object specific exposure time is used for determining values of the scan parameters for the scan of the object (150).