Hyperpolarized Gas Buffer Removal via Reactive Oxidation
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Solution Overview
Problem
Current methods for separating hyperpolarized noble gases from buffer gases are time-consuming and result in significant polarization loss, making it challenging to use gases like 129Xe and 83Kr in clinical settings due to rapid relaxation and the impracticality of cryogenic separation.
Innovation Solution
A method involving reactive removal of buffer gases, such as nitrogen or hydrogen, through oxidation or catalytic combustion, which produces a reaction product that can be easily separated from the hyperpolarized gas, maintaining the gas's polarization and reducing the need for cryogenic temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cryogenic separation is used to remove buffer gas from hyperpolarized noble gas, then the buffer gas is effectively removed, but the process is time-consuming and causes significant polarization loss (up to 1/3 of polarization is lost)
Solution Approach 1:
The patent changes the temperature parameter from cryogenic conditions to ambient temperature for the separation process. The buffer gas removal is achieved at ambient temperature through chemical reaction rather than cryogenic condensation, thereby eliminating the time-consuming cooling and heating cycles while preserving hyperpolarization
Solution Approach 2:
The patent replaces the mechanical/physical cryogenic separation system with a chemical reaction-based system. Instead of using temperature-dependent phase changes, the buffer gas is removed through chemical reactions (oxidation, combustion, or catalysis) that occur at ambient temperature, substituting a chemical mechanism for a physical one
2Quantity of substance
If cryogenic separation is used to remove buffer gas fromhyperpolarized noble gas, then the buffer gas is effectively removed, but additional relaxation during cryogenic gas handling results in polarization loss
Solution Approach 1:
The patent changes the temperature parameter from cryogenic conditions to ambient temperature for the separation process. The buffer gas removal is achieved at ambient temperature through chemical reaction rather than cryogenic condensation, thereby eliminating the time-consuming cooling and heating cycles while preservinghyperpolarization
Solution Approach 2:
The patent replaces the mechanical/physical cryogenic separation system with a chemical reaction-based system. Instead of using temperature-dependent phase changes, the buffer gas is removed through chemical reactions (oxidation, combustion, or catalysis) that occur at ambient temperature, substituting a chemical mechanism for a physical one
3Ease of manufacture
If reactive buffer gas (e.g., hydrogen or hydrocarbon) is used instead of traditional buffer gas (nitrogen or helium), then the buffer gas can be removed reactively at ambient temperature, but the buffer gas must not interfere with the SEOP process
Solution Approach 1:
The patent applies local quality by making the buffer gas reactive specifically for the separation step while maintaining compatibility with SEOP. The buffer gas has different functional properties at different stages: during SEOP it must be inert to alkali metals, but during separation it reacts readily with oxygen or oxidizing agents. This spatial/temporal differentiation of chemical reactivity resolves the contradiction
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 faster, cheaper, and less energy-intensive separation of hyperpolarized gases, preserving their polarization and enabling the use of previously impractical isotopes like 129Xe and 83Kr in clinical applications with improved MRI signal intensities.
Implementation Method 1
One method of producinghyperpolarised noble gas (hpNG) is via spin-exchange optical pumping (SEOP). In this method, the noble gas to be polarized is mixed with a buffer gas (e.g. in a ratio of 5% noble gas to 95% buffer gas) in the presence of an alkali metal vapour (e.g. rubidium or caesium). Circularly polarised light is used to excite electrons in the alkali metal, and angular momentum from those excited electrons is transferred to the noble gas, enhancing the spin polarization.
Implementation Method 2
This is mainly caused by two effects, (a) by quenching of destructive radiation from the alkali metal atoms, typically obtained through molecular nitrogen (N2)
Implementation Method 3
by increasing the lifetime of the alkali metal (electron) spin polarized state, typically achieved through dilution with helium-4 (4He) or through N2
Implementation Method 4
A method involving reactive removal of buffer gases, such as nitrogen or hydrogen, through oxidation or catalytic combustion
Implementation Method 5
A method involving reactive removal of buffer gases, such as nitrogen or hydrogen, through oxidation or catalytic combustion
Data Source
AI summary
A method of removing buffer gas from a mixture comprising the buffer gas and hyperpolarized noble gas is described. The method includes reacting the buffer gas to produce a reaction product different to the buffer gas. The buffer gas may be reactively removed by one or more of oxidation, reduction, polymerization and binding reactions with solid surfaces. The buffer gas may be molecular hydrogen and/or molecular nitrogen. Apparatus for carrying out the method are also disclosed.