CT Detector Calibration Supplemental Source
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Solution Overview
Problem
Conventional CT scanner detectors with stable gains are not suitable for applications requiring higher light output or spectral resolution, as their gain changes frequently, necessitating a different calibration approach than the traditional monthly recalibration method.
Innovation Solution
A CT imaging system with a supplemental radiation source that emits secondary radiation, allowing for continuous calibration of detector gains, even when the primary source is used for object or subject scans, by performing supplemental scans concurrently with object or subject scans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional scintillator materials with stable gain are used, then monthly calibration is sufficient, but detector gain changes frequently with newer high-performance materials
Solution Approach 1:
The system performs preliminary calibration actions by acquiring projection data from a calibration object (such as a water phantom or specialized phantom with known attenuation properties) before actual patient scans. This preliminary data collection establishes baseline detector response characteristics, allowing the system to detect and correct gain drift during routine scans without requiring frequent separate calibration procedures.
Solution Approach 2:
The calibration system uses the scanner's own operational data to perform self-calibration. By analyzing projection data acquired during normal scanning operations (including scans of patients or phantoms), the system automatically detects detector gain changes and applies corrections without requiring external calibration equipment or manual intervention, thus serving its own calibration needs.
2Measurement precision
If traditional air calibration procedures are used, then calibration can be performed periodically, but personnel are exposed to ionizing radiation during calibration scans
Solution Approach 1:
The system introduces a calibration object (such as a water phantom or specialized phantom) as an intermediary medium between the x-ray source and detectors. This phantom serves as a stable reference that attenuates x-rays in known patterns, allowing the system to measure and correct detector gain variations without requiring personnel to be present in the scanner room during calibration acquisition.
Solution Approach 2:
The system creates a digital copy or model of the calibration object's expected attenuation pattern and compares actual detector responses against this reference model. By working with digital representations and pre-acquired reference data, the system eliminates the need for personnel to physically handle calibration objects or be exposed to radiation during calibration procedures.
3Measurement precision
If high light output scintillators are used to improve signal-to-noise ratio, then detector gain becomes less stable over time
Solution Approach 1:
The system implements continuous feedback monitoring by regularly analyzing projection data from calibration objects or from uniform regions in patient scans. When detector gain drift is detected through comparison with reference values, the system automatically applies correction factors to normalize detector responses, thus maintaining measurement precision despite the inherently less stable gain characteristics of high-light-output scintillators.
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 method provides continuous and accurate detector gain calibration, reducing image artifacts and improving signal-to-noise ratio, especially in applications with low x-ray flux or high spatial resolution, and allows for repeated calibration without exposing personnel to ionizing radiation during standard air calibration procedures.
Implementation Method 1
A primary source 110, such as an x-ray tube, is supported by the rotating gantry 104 and rotates in coordination with the rotating gantry 104 about the examination region 106. The primary source 110 emits a generally fan, cone, or wedged shaped radiation beam that traverses along a path 112 from one side of the examination region 106 to the other.
Implementation Method 2
A supplemental source 114 is affixed in the stationary gantry 102. In one instance, the supplemental source 114 is located below the subject support 108. When the supplemental source 114 is actuated to emit radiation, the supplemental source 114 emits radiation that traverses only a sub-portion of the path 112.
Implementation Method 3
The scintillator array includes scintillating material that absorbs x-rays that pass through the examination region and the portion of the object or subject and produces light in proportion to the total energy of the absorbed x-rays.
Implementation Method 4
The photodiode array absorbs the light produced by the scintillating material and converts the absorbed light into an electrical current in proportion to the light absorbed.
Data Source
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AI summary
A system (100) includes a stationary gantry (102) and a rotating gantry (104), wherein the rotating gantry is rotatably supported by the stationary gantry. The rotating gantry (104) includes a primary source (110) that emits primary radiation and a detector array (116) having at least one row of detector elements (502) extending along a longitudinal axis. The primary source and the detector array are located opposite each other, across an examination region, and the primary radiation traverses a path (112) between the primary source and the detector array and through an examination region (106) and illuminates the at least one row of detector elements of the detector array, which detects the primary radiation. The system further includes a supplemental source (114), wherein the supplemental source is affixed to a non-rotating portion of the system and emits radiation that traverses a sub-portion of the path and illuminates the at least one row of detector elements of the detector array, which detects the secondary radiation.