Gamma-Ray Detector Layout for DOI and Time-of-Flight Encoding
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Solution Overview
Problem
Current gamma ray detectors face challenges in determining the depth of interaction (DOI) of gamma rays, leading to parallax errors, especially in smaller scanners, due to the thickness of scintillation crystals, which affects spatial resolution and temporal resolution, particularly in PET scanners.
Innovation Solution
A device comprising scintillation crystal blocks with elongated sheets optically coupled to photosensors, using direct optical coupling without diffusing sheets, and retroreflective films to maximize light detection, allowing precise determination of DOI, energy, and time-of-flight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If depth-of-interaction encoding is implemented using conventional methods, then depth information can be obtained, but the number of required detectors increases significantly
Solution Approach 1:
The patent introduces a temporal dimension by encoding depth information through time-of-flight measurements. Instead of using multiple detectors spatially arranged to encode depth, the system uses a single detector that measures the time it takes for photons to travel to and from different depths, thereby encoding depth information in the time domain rather than requiring additional spatial detectors.
Solution Approach 2:
The patent introduces a flying spot laser as an intermediary that scans the scene and provides time-stamped illumination. This intermediary enables the system to encode depth information temporally by knowing precisely when each location was illuminated, allowing a single detector to reconstruct depth information without requiring multiple simultaneous detectors.
2Loss of information
If conventional gamma ray detection methods are used, then detection capability is achieved, but interaction depth information cannot be determined
Solution Approach 1:
The system uses periodic pulsed illumination from a flying spot laser to encode depth information. By illuminating different locations at different times and measuring the time-of-flight of photons from each pulse, the system can determine interaction depth for each detected gamma ray event, thereby recovering depth information that would otherwise be lost in conventional continuous detection methods.
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
The device enhances spatial and temporal resolution by optimizing light detection, reducing parallax errors, and improving the accuracy of gamma ray interaction depth and time-of-flight measurements.
Implementation Method 1
a first portion of the optical photons generated by the scintillator in response to the gamma ray interaction
Implementation Method 2
a second portion of the optical photons generated by the scintillator... to a photodetector
Data Source
Figure 1(a)~2a
Figure 2b~4
Figure 5~7
AI summary
The invention relates to a device for the detection of gamma rays, presenting a high resolution in the three-dimensional position of the impact of the gamma ray within one or more scintillation crystal blocks (1) coupled to an array (2) of photosensors, for the determination of the impact energy of said gamma ray, the determination of the instant in time when said impact occurred, the interaction depth and the determination of the time-of-flight. Advantageously, in said device, the scintillation crystal detection blocks (1) are optically isolated, in such a way that the scintillation light can only exit said blocks (1) via the output region (4); and the scintillation crystal detection blocks (1) and the array (2) of photosensors are disposed in direct optical coupling.