Hyperpolarization Transfer via Cross Polarization for MRI Samples
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Solution Overview
Problem
Current hyperpolarization techniques, such as Dissolution DNP and Brute Force, face challenges with long polarization times and high power requirements, limiting the size of samples that can be prepared for in vivo MRI applications, especially for low γ / long T1 nuclei like 13C and 15N.
Innovation Solution
A method involving a solid sample with both long and short T1 nuclei, where the short T1 nuclei are hyperpolarized in the solid state using DNP or other techniques, and then transformed into a liquid state for efficient Cross Polarization transfer to the long T1 nuclei, reducing energy requirements and enabling larger sample volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Dissolution DNP is used to hyperpolarize low γ/long T1 nuclei, then polarization can be achieved, but the polarization time becomes excessively long (one hour or more)
Solution Approach 1:
The patent segments the hyperpolarization process into two distinct stages: first hyperpolarizing short T1 nuclei (high γ nuclei) which have fast polarization build-up, then transferring this polarization to long T1 nuclei (low γ nuclei) through cross-polarization. This segmentation allows the system to leverage the fast polarization of high γ nuclei to ultimately achieve the desired polarization of low γ nuclei much faster than direct DNP on the latter would require.
Solution Approach 2:
The patent introduces short T1 nuclei (high γ nuclei) as an intermediary species. These intermediary nuclei are first hyperpolarized efficiently using DNP techniques, then serve as a polarization source that transfers their hyperpolarization state to the target long T1 nuclei through cross-polarization interactions. This intermediary approach bypasses the need for direct, time-consuming DNP on the low γ/long T1 nuclei themselves.
2Reliability
If hyperpolarization is transferred from 1H to 13C nuclei in the liquid state, then polarization transfer can occur, but the required B1 field strength at two Larmor frequencies creates serious technical challenges in cryogenic region
Solution Approach 1:
The patent changes the physical state parameter of the sample from liquid to solid before performing the cross-polarization transfer. In the solid state, the cross-polarization can be achieved using standard single-frequency RF fields applied during the dissolution process, avoiding the need for complex dual-frequency B1 field generation in the cryogenic region that would be required for liquid-state transfer at two different Larmor frequencies.
3Reliability
If Brute Force hyperpolarization is applied to achieve high polarization levels, then polarization can be generated, but the polarization build-up becomes extremely slow due to large T1 values at low temperature
Solution Approach 1:
The patent segments the hyperpolarization task by first applying Brute Force or DNP to the short T1 nuclei (high γ nuclei) which have fast polarization build-up even at cryogenic temperatures. Once these intermediary nuclei are hyperpolarized, the polarization is transferred to the long T1 nuclei through cross-polarization during dissolution, thereby achieving high polarization levels without waiting for the extremely slow direct polarization build-up of the target nuclei.
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 rapid and efficient hyperpolarization of long T1 nuclei, minimizing polarization loss and enabling the preparation of larger sample volumes suitable for in vivo MRI applications with improved NMR signal strength.
Implementation Method 1
hyperpolarizing the short T1 nuclei in the solid sample... the hyperpolarization in step b) can in particular be achieved by DNP
Implementation Method 2
transferring the polarization of the short T1 nuclei to the long T1 nuclei within the molecules in the liquid sample by Cross Polarization
Data Source
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AI summary
A method for producing a hyperpolarized sample for use in a magnetic resonance investigation, with the following steps: a) providing a solid sample (50), containing long T1 nuclei and short T1 nuclei in the same molecules (51); b) hyperpolarizing the short T1 nuclei in the solid sample (50), c) transforming the solid sample (50) into a liquid sample (52), d) transferring the polarization of the short T1 nuclei to the long T1 nuclei within the molecules in the liquid sample (52) by Cross Polarization. The invention provides a method which can provide samples with hyperpolarized long T1 nuclei, in particular 13C or 15N, in a simple and efficient way.