PET DOI Detector Calibration via Optical Sensor Side Irradiation
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Solution Overview
Problem
Existing PET apparatuses with DOI detectors face challenges in calibrating scintillator crystals after assembly into a detector ring, as they cannot perform irradiation of radiation rays at each depth from the side surfaces, affecting the precision of annihilation event position estimation, especially at the edge of the field of view.
Innovation Solution
The PET apparatus includes processing circuitry that obtains detection data corresponding to the depth of interaction in DOI detectors and calibrates them based on an ideal distribution, correcting depth and time differences to improve precision without the need for irradiation at each depth from side surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If radiation rays are irradiated at each depth from side surfaces to calibrate scintillator crystals, then manufacturing precision of DOI detectors is improved, but device complexity and ease of operation deteriorate due to the need for complex irradiation equipment and procedures
Solution Approach 1:
Instead of irradiating from the side surfaces as in conventional methods, this patent inverts the approach by irradiating from the surface where optical sensors are located. The calibration light is introduced through the optical sensor side, allowing calibration without complex side-surface irradiation equipment while achieving the same calibration precision.
Solution Approach 2:
The patent uses a light source that emits calibration light similar to scintillation light produced by gamma rays. This copying approach allows calibration using optical signals that mimic the actual detection process, eliminating the need for radioactive sources and complex irradiation setups while maintaining calibration accuracy.
2Measurement precision
If radiation rays are irradiated at each depth from side surfaces to calibrate scintillator crystals, then measurement precision of interaction depth is improved, but loss of time increases due to the complex calibration procedure
Solution Approach 1:
The patent performs calibration by introducing light from the optical sensor side, which allows for quicker and simpler calibration procedures. This preliminary action establishes accurate depth information before actual PET imaging, reducing the time required for calibration while maintaining measurement precision.
Solution Approach 2:
The patent replaces the mechanical/physical process of side-surface irradiation with an optical approach where calibration light is introduced through the optical sensor side. This substitution simplifies the calibration process, reducing both the time and complexity required while maintaining depth measurement precision.
3Productivity
If DOI detectors are assembled into a detector ring without calibration, then productivity of detector assembly is improved, but measurement precision of annihilation event position deteriorates
Solution Approach 1:
The patent performs calibration after detector ring assembly by introducing light through the optical sensors. This preliminary calibration action ensures accurate depth and position information is established before actual PET imaging begins, maintaining high measurement precision while allowing flexible assembly procedures.
Solution Approach 2:
The calibration process uses the existing optical sensor infrastructure to introduce calibration light, allowing the detector system to calibrate itself without requiring external irradiation equipment. This self-service approach maintains productivity while ensuring measurement precision.
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 enables precise calibration of DOI detectors, enhancing the spatial and temporal resolution of PET imaging by correcting depth and time shifts, thereby improving the accuracy of annihilation event position estimation across the field of view.
Implementation Method 1
the gamma rays are, in the scintillator crystals, converted into scintillation light
Implementation Method 2
detected as scintillation events by the optical sensors
Data Source
AI summary
According to one embodiment, a positron emission tomography (PET) apparatus includes processing circuitry. The processing circuitry is configured to obtain a plurality of items of detection data each corresponding to a depth at which a gamma ray has caused an interaction in a plurality of depth-of-interaction (DOI) detectors. The processing circuitry is configured to calibrate the plurality of DOI detectors based on each of the obtained plurality of items of detection data and an ideal distribution of the plurality of items of detection data.