X-ray Tube Voltage Optimization for Multiphase CT
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Solution Overview
Problem
In multiphase examinations, such as those of the liver, maintaining optimal image quality while minimizing x-ray radiation dose is challenging due to varying tissue states and iodine concentrations, which require different optimal tube voltages for each phase, conflicting with the need for consistent acquisition parameters.
Innovation Solution
A method to determine tube voltage and current for each phase of a multiphase examination, maintaining a constant contrast-to-noise ratio, allowing for the selection of a tube voltage that minimizes the total x-ray radiation dose applied to the patient, while adhering to the technical limitations of the x-ray device, by using reference values and stored dependencies of tissue contrast and noise on tube voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If different optimal tube voltages are selected for each phase to minimize radiation dose, then the total x-ray radiation dose is reduced, but the acquisition parameters become inconsistent across phases
Solution Approach 1:
The patent implements dynamic selection of tube voltage based on the specific phase and tissue type being examined. The system adapts acquisition parameters for each phase (native, arterial, venous) according to the iodine concentration and tissue characteristics, rather than using fixed parameters throughout the examination. This allows optimization of radiation dose for each phase while maintaining overall examination coherence through centralized control.
Solution Approach 2:
The patent applies different tube voltage settings to different phases and tissue types within the multiphase examination. Specifically, lower tube voltages (e.g., 80-100 kV) are used for phases with high iodine concentration where contrast is enhanced, while higher voltages may be used for other phases. This localized parameter optimization reduces radiation dose in phases where it is most beneficial while maintaining image quality where needed.
2Illumination intensity
If low tube voltage is used to enhance iodine contrast, then image contrast of iodine increases, but the image noise increases
Solution Approach 1:
The patent systematically varies tube voltage as a key parameter to optimize the balance between iodine contrast and image noise. By selecting specific voltage ranges (e.g., 80-100 kV for high iodine concentration phases), the system exploits the energy-dependent photoelectric effect to enhance iodine contrast while managing noise through appropriate voltage selection. The system also adjusts tube current in conjunction with voltage to maintain optimal signal-to-noise ratio.
Solution Approach 2:
The patent employs rapid phase transitions with minimal time between phases, allowing the system to capture all necessary information at optimized parameters for each phase before tissue characteristics change significantly. This approach enables the use of low tube voltages for contrast enhancement in iodine-rich phases without requiring prolonged exposure that would accumulate noise.
3Object-affected harmful factors
If tube voltage is adjusted to minimize dose in each phase, then dose optimization is achieved, but the complexity of parameter selection increases
Solution Approach 1:
The patent performs preliminary classification of the examination protocol into distinct phases (native, arterial, venous) with predetermined optimal parameter ranges before the actual scanning begins. Based on the selected examination type and tissue characteristics, the system pre-configures appropriate tube voltage settings for each phase, eliminating the need for complex real-time parameter adjustments during scanning. This advance planning simplifies the operational complexity while maintaining dose optimization.
Solution Approach 2:
The patent incorporates feedback mechanisms where the system monitors the actual iodine concentration and tissue characteristics during the examination and adjusts tube voltage settings accordingly. The image quality and dose metrics from preliminary scans or reference data are used to fine-tune parameters for subsequent phases, creating a closed-loop system that automatically optimizes parameters without requiring complex manual intervention.
Data Source
AI summary
The value of a tube voltage of an x-ray tube, used to acquire x-ray projections of a patient in order to generate at least one image in each phase of a multiphase examination, is determined from a contrast-to-noise ratio that establishes the desired image quality of the image in each phase, and the tube current for each tube voltage for each phase is determined given a constantly maintained contrast-to-noise ratio for different tube voltages. For each phase, a value for the dose of x-ray radiation is defined for each different tube voltage and the associated determined tube current. From among the different tube voltages, a tube voltage is set that causes the total dose of x-ray radiation applied to the patient to be as low as possible for all phases of the examination.