Variable Thickness Light Guide for PET Detector Edge Effects
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Solution Overview
Problem
Conventional PET detectors face limitations in light distribution and collection due to uniform layouts of photosensors, which fail to compensate for locally varying light distributions and edge effects, leading to inefficiencies in gamma ray detection and reconstruction accuracy.
Innovation Solution
A gamma ray detector module design featuring a light guide with a narrow portion positioning a first light sensor closer to the crystal element than others, and angled recessed portions to tilt adjacent sensors, optimizing light distribution and utilization of the photocathode surface for improved signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform layouts of photosensors are used, then device complexity is reduced and ease of manufacture is improved, but light distribution becomes unbalanced and edge effects are not compensated
Solution Approach 1:
The patent applies local quality by varying the light guide thickness at different locations to compensate for position-dependent light collection efficiency. The light guide thickness is increased at edge regions and decreased at center regions, creating location-specific optical paths that balance the light distribution across all photosensors regardless of their position in the array.
Solution Approach 2:
The patent introduces asymmetry in the light guide structure by using different thicknesses for different photosensor positions. This asymmetric design compensates for the symmetric uniform layout's deficiency in handling edge effects, where photosensors at different positions naturally receive different amounts of light due to geometric factors.
2Device complexity
If uniform light guide thickness is used, then device complexity is reduced, but light collection efficiency varies across sensors due to position-dependent effects
Solution Approach 1:
The light guide is designed with location-specific thickness properties, where the thickness varies according to the position of the underlying photosensor. This local optimization ensures that each photosensor receives a balanced amount of light, improving detection accuracy while maintaining a relatively simple overall structure.
3Ease of manufacture
If photosensors are positioned at uniform distances from crystal elements, then manufacturing is simplified, but edge effects cause unbalanced light distribution and reduced reconstruction accuracy
Solution Approach 1:
The patent implements local quality by positioning photosensors at variable distances from the crystal elements through the variable thickness light guide. Photosensors at edge positions are placed closer to the crystal elements (thinner light guide), while center photosensors are placed farther (thicker light guide), compensating for edge effects and preserving reconstruction accuracy.
Solution Approach 2:
The patent applies preliminary anti-action by pre-compensating for edge effects through the variable light guide thickness design. Before light detection occurs, the optical path lengths are deliberately adjusted to counteract the expected position-dependent light collection inefficiencies, ensuring balanced signal distribution across all photosensors.
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 design enhances light collection and signal quality by balancing light distribution across sensors, compensating for asymmetries and edge effects, resulting in improved spatial and timing resolution in PET imaging.
Implementation Method 1
a light guide arranged between the at least one crystal element and the plurality of light sensors, the light guide being optically connected to the at least one crystal element
Implementation Method 2
The radionuclide emits positrons, and when an emitted positron collides with an electron, an annihilation event occurs, wherein the positron and electron are destroyed. Most of the time, an annihilation event produces two gamma rays (at 511 keV)
Data Source
AI summary
A gamma ray detector module that includes at least one crystal element arranged in a plane, a plurality of light sensors arranged to cover the at least one crystal element and to receive light emitted from the at least one crystal element, and a light guide arranged between the at least one crystal element and the light sensors, the light guide being optically connected to the at least one crystal element. Further, the light guide includes a narrow portion that positions at least one light sensor of the plurality of light sensors closer to the at least one crystal element than other light sensors of the plurality of light sensors. In addition, the light guide may include an angled recessed portion that positions another light sensor at an oblique tilt angle with respect to the plane of the at least one crystal element.