PCCT Material Density Calibration Across Focal Spot Sizes
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Solution Overview
Problem
The generation of calibration vectors for photon counting computed tomography (PCCT) systems is time-consuming, leading to customer downtime and reduced availability of the system for patient scans, particularly due to the complexity and time required for material decomposition (MD) calibration vectors, which are dependent on focal spot size.
Innovation Solution
A method that reduces the number of MD calibration scans by generating common sets of MD calibration vectors applicable to various focal spot sizes, reducing the time spent on calibration while maintaining image quality, and using these vectors during image reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate MD calibration vectors are generated for each focal spot size, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies universality by generating a single set of MD calibration vectors that can be used across multiple focal spot sizes. Instead of creating separate calibration vectors for each focal spot size (which would be time-consuming), the system develops universal calibration vectors that work for different focal spot configurations, reducing calibration time while maintaining adequate measurement precision
Solution Approach 2:
The patent utilizes parameter changes by varying the focal spot size parameter during calibration scans while using a single MD calibration vector set. The system acquires calibration data across different focal spot sizes and energy levels, then applies parameter transformations to create energy-dependent calibration vectors that can be applied regardless of the specific focal spot size used during imaging
2Manufacturing precision
If multiple calibration scans are performed for different focal spot sizes, then manufacturing precision is improved, but productivity decreases
Solution Approach 1:
The patent implements universality by creating a universal MD calibration vector set that serves multiple focal spot sizes. This approach maintains calibration accuracy across different focal spot configurations while significantly reducing the number of calibration scans required, thereby improving system availability and productivity
Solution Approach 2:
The patent applies preliminary action by performing comprehensive calibration scans at multiple energy levels and focal spot sizes during the initial calibration phase. This preliminary data collection enables the system to generate universal calibration vectors that can be applied to subsequent scans without requiring additional focal spot-specific calibration scans, thus 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 decreases the time spent on MD calibration by up to 60% and increases the availability of the PCCT system for patient scans by minimizing the number of MD calibration scans and corresponding vectors, while ensuring desired image quality.
Implementation Method 1
an electron beam generated by a cathode is directed towards a target within an X-ray tube
Implementation Method 2
A fan-shaped or cone-shaped beam of X-rays produced by electrons colliding with the target
Implementation Method 3
After being attenuated by the object, the X-rays impinge upon an array of X-ray detectors
Implementation Method 4
using Photon Counting CT (PCCT), where the X-ray detectors are photon counting detectors, and photons are counted to provide spectral information
Data Source
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Figure 3A
AI summary
Methods and systems are provided for calibrating a photon counting computed tomography (PCCT) system (100, 200). To reduce an amount of calibration data stored in a memory of the PCCT system (100, 200), and to reduce a time spent calibrating the PCCT system (100, 200), a method (600, 700) is provided for using a material decomposition (MD) calibration vector generated for a first focal spot size to correct projection data acquired using the PCCT system at different focal spot sizes. To compensate for spectral differences due to focal spot size, the projection data is corrected and normalized by air calibration vectors generated for each different focal spot size.