SPECT Gamma Camera Calibration Using Exam-Derived Pixel Maps
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Solution Overview
Problem
Current SPECT imaging systems require costly and hazardous uniform sources for calibration, which decay and need frequent replacement, and the calibration process consumes technician time and exposes them to radiation, while also delaying patient scans.
Innovation Solution
A computer-implemented method that uses data from previous SPECT imaging examinations to calibrate pixel energy, uniformity, and bad pixels without a uniform source, utilizing energy and uniformity calibration maps populated with factors derived from accumulated pixel data, and replacing bad pixel values with neighboring pixel values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If uniform sources are used for calibration, then calibration accuracy is improved, but system cost increases and radiation exposure occurs
Solution Approach 1:
The patent creates a virtual copy of the uniform source by using computer-generated projection data that simulates what a uniform source would produce. This virtual phantom replicates the calibration function without requiring physical radioactive material, thereby eliminating radiation exposure while maintaining calibration accuracy.
Solution Approach 2:
The patent replaces the physical mechanical uniform source (radioactive material) with a computational model. By using software-generated projection data and algorithms to simulate uniform source behavior, the system substitutes a computational approach for the physical radioactive source, eliminating the need for hazardous materials.
2Measurement precision
If uniform sources are used for calibration, then calibration can be performed, but the source decays and requires frequent replacement increasing cost
Solution Approach 1:
The virtual phantom creates a permanent, non-decaying copy of the uniform source in digital form. This computational replica maintains consistent properties indefinitely without the decay characteristics of radioactive materials, eliminating the need for periodic source replacement.
Solution Approach 2:
The patent replaces expensive, short-lived radioactive sources with a free, infinite-duration computational model. The virtual phantom has no physical consumption or degradation, providing an economically sustainable calibration solution that eliminates ongoing source replacement costs.
3Measurement precision
If calibration is performed using uniform source, then detector calibration is achieved, but technician time is consumed and patient scans are delayed
Solution Approach 1:
The patent performs calibration actions in advance by pre-generating virtual phantom projection data that can be stored and reused. The calibration computations are completed beforehand, allowing rapid application of calibration factors without requiring time-consuming physical source measurements during patient scan schedules.
Solution Approach 2:
The patent replaces time-consuming physical calibration procedures with rapid computational algorithms. By using software-based virtual phantom processing instead of physical source measurements, the system achieves calibration in minutes rather than hours, significantly improving scan throughput.
4Measurement precision
If uniform source is used for calibration, then energy and uniformity calibration maps can be created, but the source exposes technician to ionizing radiation
Solution Approach 1:
The patent creates accurate calibration maps using a virtual copy of the uniform source instead of physical radioactive material. The computer-generated projection data from the virtual phantom produces identical calibration information without any ionizing radiation, protecting technician health while maintaining map accuracy.
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 eliminates the need for uniform sources, reduces costs, minimizes radiation exposure, and allows continuous calibration, ensuring accurate imaging without delaying patient scans.
Implementation Method 1
detects gamma rays emitted by a radiopharmaceutical administered to a patient
Implementation Method 2
a uniform source (e.g., Cobalt-57 (Co-57), Technetium-99m (Tc-99m), etc.) is positioned in the examination region
Data Source
AI summary
A method includes accumulating counts for each pixel in a set of pixels of one or more gamma cameras of a SPECT imaging system from a plurality of imaging examinations and each energy peak of each isotope used in the plurality of imaging examinations to produce an energy spectrum for each of the pixels at each of the energy peaks of each of the isotopes, determining, for the pixels and for the energy peaks, an energy calibration factor that converts an energy detected by each of the pixels to an energy of a corresponding energy peak and populating an energy map with the factors, and determining, for the pixels and for the energy peaks, a uniformity calibration factor that converts a number of counts detected by each of the pixels to a predetermined number of counts for a corresponding energy peak and populating a uniformity map with the factors.