Tungsten Collimator Fabrication via EDM
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Solution Overview
Problem
Current photon collimators for medical imaging, particularly those made from lead alloys, are difficult to fabricate with the precision and cost-effectiveness required for human-sized equipment, as tungsten and molybdenum alloys are hard to machine and require complex grid patterns that are time-consuming and expensive to produce using existing methods.
Innovation Solution
A photon collimator constructed from tungsten, molybdenum, or other photon-attenuating alloys, featuring integrally formed septa slats with elongated lengths and oriented in an opposed pattern array, where aperture channels are defined between slats, allowing for efficient fabrication using electric discharge machining or laser thermal ablation, reducing the need for individual aperture formation and enabling precise alignment with fewer forming operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten or molybdenum alloys are used to replace lead alloys in collimators, then the photon attenuation performance is improved, but the fabrication difficulty increases due to material hardness and high melting temperature
Solution Approach 1:
The patent replaces traditional mechanical machining methods with electric discharge machining (EDM) to fabricate collimators from hard materials like tungsten and molybdenum. EDM uses electrical discharges to erode material, eliminating the need for mechanical cutting tools that would be ineffective against these hard, high-melting-point materials. This substitution enables precise fabrication of complex aperture patterns in materials that were previously difficult to machine.
Solution Approach 2:
The patent changes the fabrication approach by using thermal energy parameters (electrical discharge, laser heating) instead of mechanical parameters (cutting forces, tool wear). This allows the material to be removed through controlled melting and vaporization rather than mechanical abrasion, making it feasible to work with tungsten and molybdenum alloys that have high melting temperatures and extreme hardness.
2Manufacturing precision
If individual apertures are machined one-by-one in a large collimator grid, then the aperture precision is maintained, but the fabrication time and cost increase significantly
Solution Approach 1:
The patent segments the collimator fabrication process into two stages: first, a complete grid pattern is machined through the entire block in one operation using EDM or laser; second, individual aperture holes are cleaned out. This segmentation allows the time-consuming precision work to be done once on the entire grid structure rather than repeatedly on each individual aperture, dramatically reducing total fabrication time while maintaining precision.
Solution Approach 2:
The patent performs preliminary action by pre-machining the complete grid pattern of septa walls before forming the individual aperture holes. This preliminary structuring creates a framework that guides subsequent aperture formation and ensures precise spacing and alignment of all apertures without requiring each one to be individually positioned and machined.
3Manufacturing precision
If complex grid patterns are fabricated using traditional methods, then the aperture alignment precision is achieved, but the fabrication cost increases
Solution Approach 1:
The patent replaces expensive mechanical machining operations with electric discharge machining or laser processing. These thermal/electrical methods can create complex three-dimensional grid patterns and precise aperture geometries more efficiently than traditional mechanical milling or drilling, reducing both tooling costs and labor expenses while maintaining or improving alignment 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 allows for the cost-effective fabrication of collimators with high precision, reducing the time and expense associated with producing complex grid patterns, while maintaining the necessary aperture tolerances for human-sized medical imaging equipment.
Implementation Method 1
A photon collimator constructed from tungsten, molybdenum, or other photon-attenuating alloys, featuring integrally formed septa slats with elongated lengths and oriented in an opposed pattern array, where aperture channels are defined between slats, allowing for efficient fabrication using electric discharge machining or laser thermal ablation
Implementation Method 2
A photon collimator constructed from tungsten, molybdenum, or other photon-attenuating alloys, featuring integrally formed septa slats with elongated lengths and oriented in an opposed pattern array, where aperture channels are defined between slats, allowing for efficient fabrication using electric discharge machining or laser thermal ablation
Data Source
AI summary
A photon collimator, suitable for use in medical imaging equipment, is constructed from a block of photon-attenuating material, such as solid tungsten or molybdenum alloy that defines a plurality of integrally formed septa slats. Each slat has an elongated length dimension greater than thickness and depth dimensions, and is oriented in an opposed pattern array that is laterally spaced relative to its respective thickness dimension. An aperture channel is defined between each pair of opposed slats. Rows of integrally formed slats in one block or separately affixed blocks may be stacked on each other at skewed angles to form two-dimensional grids of apertures having polygonal cross sections. The slats may be formed by electric discharge or laser thermal ablation machining, such as by a sequential passing of an EDM wire cutting head along the pattern array, repeating sequential cutting of respective channel depth and width.