Ce3+ Activated Luminescent Compositions for Imaging Systems
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Solution Overview
Problem
Current luminescent compositions for imaging systems, such as CT and PET scanners, have long decay times which result in longer imaging times and lower resolution due to broader afterglow spectra, limiting the number of detectable scintillation events and temporal resolution.
Innovation Solution
Development of Ce3+ sensitized luminescent compositions with low crystal-field splitting and covalent interaction, specifically fluorides and phosphates like A(Y1-x-yLuxLay)F4, A(Y1-x-yLuxLay)3F10, and BaCa(Y1-x-yLuxLay)2F10, which exhibit shorter decay times and narrower afterglow spectra, enhancing imaging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional luminescent compositions (e.g., Ce3+ doped inorganic host matrices like Lu2SiO5, LuPO4, Lu2Si2O7) are used, then high stopping power is achieved due to high density, but decay time is long resulting in lower temporal resolution and broader afterglow spectra
Solution Approach 1:
The patent changes the chemical composition parameters by introducing specific fluoride and sulfate host matrices (e.g., A(Y1-x-yLuxLay)F4, BaCa(Y1-x-yLuxLay)2F10) with different crystal structures and bonding characteristics. These compositional changes result in shorter decay times (e.g., 45-65 ns compared to longer decay times of conventional materials) while maintaining high stopping power through high density (e.g., 4.27-5.70 g/cm³), thus resolving the contradiction between stopping power and decay time.
2Reliability
If conventional luminescent compositions are used, then high density providing high stopping power is achieved, but afterglow spectrum is broad reducing the number of detectable scintillation events
Solution Approach 1:
The patent modifies the luminescent material parameters by selecting host matrices with specific crystal structures (tetragonal, cubic) and bonding types (ionic-covalent). These parameter changes produce narrower afterglow spectra with peak emissions in the 280-400 nm ultraviolet range, which increases temporal resolution and allows more scintillation events to be detected within a given time period, while maintaining high stopping power through high density.
3Productivity
If luminescent compositions with high light yield are used, then imaging efficiency is improved, but decay time increases leading to longer imaging times
Solution Approach 1:
The patent optimizes the material parameters by selecting host matrices with specific crystal structures and Ce3+ doping concentrations. These changes achieve high light yield (high number of photons per MeV) combined with short decay times (45-65 ns). The short decay time allows the imaging system to process more events per unit time, thereby reducing imaging time and increasing productivity without sacrificing imaging efficiency.
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
These compositions reduce imaging time, increase resolution, and enhance the number of detectable scintillation events by shortening decay times and narrowing the afterglow spectrum, leading to improved imaging performance.
Implementation Method 1
Luminescent compositions function to harness the energy of incoming high energy radiation photons (e.g. x-rays or gamma rays) and transform that energy to secondary radiation photons (e.g. ultraviolet light) which can more easily be measured by electronic photodetectors such as a photodiode or photomultiplier. Each such transformation is called a scintillation event.
Implementation Method 2
These luminescent compositions include for example scintillating compositions in which Ce3+ is located on crystallographic sites exerting a low crystal-field splitting and a low covalent interaction with the activator. Typical examples are fluorides, sulphates, and phosphates, in particular the following fluorides: A(Y1-x-yLuxLay)F4
Data Source
AI summary
A luminescent composition includes a host matrix sensitized by Ce3+ and showing emission in the ultraviolet range. Typical host matrices include fluorides, sulphates, and phosphates, in particular A(Y1-x-yLuxLay)F4, A(Y1-x-yLuxLay)3F10, BaCa(Y1-x-yLuxLay)2F10, and Ba(Y1-x-yLuxLay)2F8, wherein A=Li, Na, K, Rb, or Cs. One or more of these luminescent compositions may be applied as a ceramic or single crystalline converter for CT, PET or SPECT scanners, or as a luminescent powder layer for x-ray intensifying screens.