CT Focal Point Correction Using X-Ray Energy Spectrum
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Solution Overview
Problem
Conventional X-ray CT apparatuses face challenges in accurately specifying the focal point position of the X-ray tube during a CT scan due to thermal expansion, which can be exacerbated by the use of a pin hole collimator, leading to inaccuracies in image reconstruction.
Innovation Solution
An X-ray CT apparatus that utilizes a storage circuitry to maintain a table correlating energy spectra with focal point positions, enabling the processing circuitry to specify the corrected focal point position based on real-time energy spectrum data without relying on a pin hole collimator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pin hole collimator is used to specify the focal point position, then the focal point position can be measured, but the measurement precision deteriorates due to thermal expansion effects
Solution Approach 1:
The patent changes the measurement parameter from direct geometric position measurement using a pin hole collimator to energy spectrum-based measurement. By detecting changes in the energy spectrum caused by focal point position deviations and correlating them with a pre-stored table of energy spectra versus positions, the system achieves more reliable and precise focal point position specification without being affected by thermal expansion issues that plague mechanical collimator-based methods.
2Measurement precision
If a pin hole collimator is used to specify the focal point position, then the focal point position can be determined, but the device complexity increases
Solution Approach 1:
The patent extracts and removes the pin hole collimator from the system entirely. Instead of using a mechanical collimator to define and measure the focal point position, the invention utilizes the existing X-ray detector's energy spectrum detection capability. The focal point position information is extracted indirectly through energy spectrum analysis and comparison with a pre-stored reference table, eliminating the need for complex mechanical collimation hardware.
3Measurement precision
If energy spectrum data is used to specify the focal point position, then the measurement precision improves, but the loss of time increases due to data processing
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing a comprehensive table of energy spectra corresponding to various focal point positions before actual CT scanning begins. During the scan, when focal point position specification is needed, the system simply compares the current energy spectrum measurement against this pre-stored reference table to quickly identify the matching position, avoiding time-consuming real-time calculations and significantly reducing processing delays.
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 allows for precise focal point position determination during a CT scan, enhancing the accuracy of image reconstruction and reducing the need for additional collimation, thereby improving image quality and reliability.
Implementation Method 1
an X-ray detector 13 configured to detect the X-rays 124
Implementation Method 2
obtain third information about an energy spectrum of X-rays emitted from the X-ray tube 12a
Data Source
AI summary
An X-ray Computed Tomography (CT) apparatus according to an embodiment includes storage circuitry and processing circuitry. The storage circuitry is configured to store therein a table keeping first information about an energy spectrum of X-rays in correspondence with second information about a focal point position of an X-ray tube. The processing circuitry is configured to obtain third information about an energy spectrum of X-rays emitted from the X-ray tube. The processing circuitry is configured to specify a corrected focal point position on the basis of the third information and the table.