Photon-Counting X-Ray Detector Segmentation for Spectrum Correction
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Solution Overview
Problem
In photon-counting-type X-ray CT apparatuses, variations in the X-ray energy spectrum from the X-ray tube lead to difficulties in reconstructing tomograms at each energy or energy band, as existing methods cannot accurately correct for changes in X-ray dosage across different energy ranges.
Innovation Solution
The apparatus employs a configuration with a first and second X-ray detector, count result acquisition circuitry, memory circuitry, estimation circuitry, correction circuitry, and reconstruction circuitry to estimate the X-ray tube voltage or current based on energy spectra, allowing for correction of the first count data using the calculated energy spectrum, thereby enabling precise reconstruction of tomograms at each energy or energy band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photon-counting-type X-ray detector is used to acquire tomograms at each energy or energy band, then energy-specific imaging capability is improved, but the ability to correct variations in X-ray energy spectrum is lost
Solution Approach 1:
The detector is divided into multiple detection regions (first detection region and second detection region) that separately detect different portions of the X-ray spectrum. This segmentation allows independent measurement of total X-ray dosage and energy spectrum information, enabling both energy-specific imaging and correction of spectrum variations.
Solution Approach 2:
A second detection region acts as an intermediary that measures the X-ray energy spectrum without being affected by the subject. This intermediary measurement provides reference data for correcting the energy spectrum variations in the primary detection region, enabling accurate reconstruction at each energy band.
2Ease of operation
If an integration-type X-ray detector is used, then correction for total X-ray dosage is simple, but energy spectrum information is lost
Solution Approach 1:
The detector is segmented into multiple detection regions with different functions: one region performs simple integration for total dosage measurement, while another region performs energy-resolved detection. This segmentation maintains the simplicity of integration-type correction while recovering energy spectrum information through the additional detection region.
3Measurement precision
If dual-energy imaging is performed by switching X-ray tube voltage, then energy information can be specified, but correction of energy spectrum variations cannot be achieved
Solution Approach 1:
The second detection region serves as an intermediary that continuously monitors the X-ray energy spectrum regardless of tube voltage switching. This intermediary measurement provides the necessary correction data to compensate for energy spectrum variations caused by voltage switching, enabling accurate dual-energy imaging.
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 solution effectively corrects variations in the X-ray energy spectrum, allowing for accurate reconstruction of tomograms at each energy or energy band, improving the fidelity of medical image data generated by the X-ray CT apparatus.
Implementation Method 1
a first X-ray detector (31a) configured to count X-ray photons in a first region of the radiated X-rays, and to acquire energy of the X-ray photons
Implementation Method 2
a second X-ray detector (31b) configured to count X-ray photons in a second region of the radiated X-rays, and to acquire energy of the X-ray photons
Data Source
AI summary
An X-ray computed tomography apparatus according to an embodiment stores a plurality of reference count data indicative of energy spectra of X-rays, which are associated with a plurality of tube voltages or tube currents. Estimation circuitry estimates a tube voltage or a tube current at a time of X-ray irradiation, based on a comparison of energy spectra between second count data and each of the plurality of reference count data. Correction circuitry corrects first count data acquired together with the second count data, by using an energy spectrum calculated based on the estimated tube voltage or tube current. Reconstruction circuitry reconstructs medical image data, based on the corrected first count data.