CT Rotation Axis Coordinate Adjustment via Interactive Reconstruction
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Solution Overview
Problem
Existing radiation CT apparatuses face challenges in accurately calculating the coordinates of the rotation axis, leading to 'rotation axis runout' issues, especially at high magnification, which results in blurred tomograms and require repetitive calibration and scanning processes.
Innovation Solution
A radiation CT apparatus with a screen display and instruction input system that allows operators to adjust the rotation axis coordinates interactively, using temporary coordinates for initial reconstruction and shifting them to correct any errors, enabling a single CT scan to produce clear tomograms without rotation axis runout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phantom for calibrating the position of the projected rotation axis is used to calculate the coordinates, then the position can be determined, but the correct values cannot be calculated due to the effects of the diameter of the tungsten wire or the shift of the focal point during calibration, particularly when an image is taken with high magnification
Solution Approach 1:
The patent introduces an intermediary computational process that separates the calibration data collection from the final coordinate determination. Instead of directly using phantom wire projection data, the system collects projection data from the phantom, performs arithmetic operations to generate sinogram data, and then uses curve fitting or other computational methods to derive the rotation axis coordinates. This intermediary process filters out the harmful effects of wire diameter and focal point shifts.
Solution Approach 2:
The patent replaces the direct mechanical/geometric measurement approach (using the physical position of the tungsten wire in the phantom) with a computational/mathematical approach. By using arithmetic operations on projection data and analyzing sinogram patterns, the system calculates the rotation axis coordinates without being influenced by the physical dimensions of the calibration phantom components.
2Ease of operation
If coordinates of the projected rotation axis are found in advance through interpolation or extrapolation for multiple positional relationships, then the process is simplified, but the correct values cannot be found when any one value includes an error, and time elapsed affects results due to chronological shift of the apparatus
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors and adjusts the rotation axis coordinates based on the actual projection data collected during each scanning operation. Rather than relying on pre-calculated values from previous operations, the system uses the current scanning data to refine and update the coordinate information, ensuring that chronological shifts in apparatus position are compensated for in real-time.
Solution Approach 2:
The patent performs preliminary data collection during the scanning process itself. By collecting projection data that includes information about the actual apparatus positioning during the scan, the system prepares the necessary information for accurate coordinate determination before the final image reconstruction occurs. This preliminary action ensures that the coordinate data reflects the actual state of the apparatus during image acquisition.
3Reliability
If conventional calibration methods are used, then calibration can be performed, but repetitive calibration and scanning processes are required to eliminate rotation axis runout, increasing time and effort
Solution Approach 1:
The patent merges the calibration process with the actual scanning process. By collecting projection data from the calibration phantom during the scanning operation and using this data to determine rotation axis coordinates, the system eliminates the need for separate calibration and scanning steps. This combination allows the system to achieve reliable tomogram quality in a single operational pass, significantly improving productivity.
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 the generation of clear, definitive tomograms without rotation axis runout through a simple operation, significantly reducing time and effort, especially in cone-beam CT scans, by enabling precise adjustment of rotation axis coordinates during reconstruction.
Implementation Method 1
a radiation source and a radiation detector that are provided so as to face each other... the rotational table is irradiated with radiation from the source while rotating... the output from the radiation detector is taken in
Data Source
AI summary
A radiation CT apparatus that can gain a clear tomogram without a rotation axis runout and without fail through a single CT scan and a simple operation is provided. When the data on the projection with radiation collected through a CT scan is first reconstructed through an arithmetic operation by a reconstruction arithmetic operation unit 13, temporary coordinates that have been set in advance as the coordinates of the projected rotation axis so as to construct a tomogram along a predetermined sliced surface are used, this tomogram is displayed on the screen for changing the rotation axis coordinates that include the temporary coordinates, and the coordinates of the projected rotation axis are shifted by any amount in any direction through an operation on the screen so that a reconstruction arithmetic operation is again carried out in the reconstruction arithmetic operation unit 13.