Overlapping Light Guide PET Detector Modules
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Solution Overview
Problem
The installation of photomultiplier tubes (PMTs) in positron emission tomography (PET) scanners is time-consuming and prone to weak bonding due to the need for tedious mounting and gluing processes, especially for shared PMTs between modules, which can decouple under thermal or mechanical stress.
Innovation Solution
The use of overlapping and underlapping light guides with interfacing structures allows for preassembled modules to be coupled together, eliminating seams and enabling PMTs to be glued in place before installation, with optical grease used for coupling during assembly, ensuring strong and stable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PMTs are glued to light guides during assembly with conventional approaches, then PMTs can be mounted in place, but assembly time becomes lengthy (1.5 to 2.5 hours per row) and shared PMTs may decouple under thermal or mechanical stress
Solution Approach 1:
PMTs are pre-glued to light guides in a controlled environment before assembly, allowing optimal bonding conditions to be achieved. This preliminary bonding action eliminates the need for time-consuming on-site gluing and ensures stronger bonds by avoiding the constraints of gantry installation procedures.
Solution Approach 2:
The light guide assembly is divided into modular segments with overlapping structures. Each segment can be pre-assembled and tested independently, then quickly installed as a complete unit. This segmentation allows parallel processing and reduces overall assembly time while maintaining bonding integrity through standardized interfaces.
2Manufacturing precision
If shared PMTs are installed after light guides are mounted in the gantry, then accurate placement can be achieved, but the installation becomes tedious and time-consuming
Solution Approach 1:
Shared PMTs are pre-positioned and pre-glued to light guides during manufacturing, ensuring precise placement in a controlled environment. The overlapping light guide design maintains alignment features that preserve placement accuracy during subsequent assembly operations.
Solution Approach 2:
Overlapping light guide structures serve as intermediaries that maintain precise positioning of shared PMTs during assembly. The overlapping design provides mechanical guidance and alignment features that ensure accurate placement without requiring time-consuming manual adjustment during installation.
3Adaptability or versatility
If PMTs are glued over a seam between two light guides, then shared PMTs can be installed, but bonding strength is reduced and decoupling may occur due to thermal or mechanical stress
Solution Approach 1:
Shared PMTs are pre-glued to light guides in a controlled manufacturing environment where optimal bonding conditions can be achieved. This preliminary action ensures strong bonds before the PMTs are subjected to the thermal and mechanical stresses of installation and operation.
Solution Approach 2:
The overlapping light guide design merges the bonding interfaces of adjacent modules, eliminating seams at shared PMT locations. By combining the light guide structures with overlap rather than abutment, the design removes the weak bonding zone that would otherwise exist at the seam between modules.
4Ease of manufacture
If conventional gluing methods are used for shared PMTs, then installation can be completed, but bonding is weaker and may decouple under stress
Solution Approach 1:
PMTs are pre-glued to light guides during manufacturing using optimized bonding procedures. This preliminary action allows the use of best-practice gluing methods in a controlled environment, ensuring strong and reliable bonds without complicating the subsequent installation process.
Solution Approach 2:
Overlapping light guide structures act as intermediaries that protect and reinforce the bonding of shared PMTs. The overlap provides additional structural support and distributes mechanical stresses away from the PMT bonding interfaces, enhancing reliability without requiring changes to the gluing process itself.
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 significantly reduces construction time, enhances structural and thermal stability, and ensures strong bonding of shared PMTs, preventing decoupling, thus improving the efficiency and reliability of PET detector module assembly.
Implementation Method 1
The overlapping structures of each of the plurality of overlapping light guides interfaces with a underlapping structure of each of two of the plurality of underlapping light guides
Implementation Method 2
PMTs are glued to the light guides with optical cement during assembly
Data Source
AI summary
When constructing a nuclear detector module in a gantry, a plurality of overlapping light guide modules (10) are mounted to the gantry in a spaced-apart fashion, and a plurality of underlapping light guide modules (12) are mounted in between each pair of overlapping light guide modules (10). Each of the underlapping modules and the overlapping modules includes a scintillation crystal array (16) on an interior surface thereof, and a plurality of PMTs on an exterior surface thereof. Overlapping modules (10) have overlapping structures (22) that interface with underlapping structures (18) on the underlapping modules (12) and thereby eliminate a seam directly beneath PMTs that overlap the crystal arrays of both an overlapping module and an underlapping module. Optical grease is used to form a resilient grease coupling and reduce light scatter between the underlapping and overlapping modules.