PET Device Time Calibration via Rising Edge Slope
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Solution Overview
Problem
In Positron Emission Computed Tomography (PET) devices, the varying ability of tissues to absorb isotope-labeled drugs leads to different gamma photon intensities, affecting the accuracy of reconstructed images, as current calibration methods do not adequately account for the time information of photon signals.
Innovation Solution
A method is developed to calibrate time information in PET devices by determining the rising edge slope of electrical signals corresponding to photons, using a correspondence between the rising edge slope and time shift, which allows for accurate reconstruction of PET images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods are used without considering time information, then the device complexity is reduced, but the measurement precision of photon time information deteriorates
Solution Approach 1:
The patent applies preliminary action by establishing a correspondence relationship between rising edge slope and time shift before actual measurement. The calibration curve is pre-built using standard photons with known time information, allowing the system to store multiple sets of correspondence data between rising edge slopes and time shifts. During actual operation, the system simply queries this pre-established correspondence table rather than performing complex real-time calculations, thus improving measurement precision while avoiding excessive computational complexity.
Solution Approach 2:
The patent introduces an intermediary approach by using the rising edge slope as an intermediate parameter to connect the electrical signal characteristics with the time shift calibration. Instead of directly measuring time shift from raw electrical signals, the system first extracts the rising edge slope characteristic, then uses this intermediate parameter to query the pre-established correspondence relationship. This intermediary step simplifies the measurement process while maintaining high precision.
2Measurement precision
If time calibration based on rising edge slope is implemented, then the measurement precision of photon signals is improved, but the calculation complexity increases
Solution Approach 1:
The system performs preliminary calculation by pre-establishing the correspondence relationship between rising edge slope and time shift using standard photons. Multiple calibration data points are collected in advance and stored as a lookup table. During actual photon measurement, the system only needs to calculate the rising edge slope and query the pre-computed correspondence table, avoiding the need for complex iterative calculations during real-time operation.
Solution Approach 2:
The patent uses copying by creating a digital model of the calibration relationship through the correspondence table. Instead of performing complex physical measurements and calculations for each photon, the system copies the pre-established mathematical relationship between rising edge slope and time shift into a searchable data structure. This allows rapid retrieval of calibration parameters without repeating the complex measurement and calculation process.
3Measurement precision
If multiple comparison thresholds are used to determine rising edge slope, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the rising edge detection process into multiple discrete threshold levels. Instead of using a single threshold that may be affected by noise or signal variations, the system uses multiple comparison thresholds (e.g., first threshold and second threshold) to sample different points on the rising edge. This segmented approach allows for more accurate calculation of the rising edge slope by comparing multiple threshold crossing points, thereby improving measurement precision while keeping each individual comparator circuit relatively simple.
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 enhances the accuracy and quality of PET images by improving the calibration of time and energy information from gamma photons, leading to better diagnostic and treatment outcomes.
Implementation Method 1
The photon signal can be converted into an electrical signal such as current or voltage by a photoelectric converter
Data Source
AI summary
A method of calibrating time in a Positron Emission Computed Tomography (PET) device includes determining a rising edge slope of an electrical signal corresponding to a photon which is detected by a detector of the PET device when the PET device is used to scan a part of a subject to be examined. The method includes determining a time shift corresponding to the rising edge slope based on a correspondence between the rising edge slope and the time shift; calibrating time information of the photon based on the time shift; and reconstructing a PET image of the part of the subject to be examined based on the calibrated time information of the photon.