Pulse EPR Imaging Sequence for Faster T1/T2 Relaxation Mapping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pulse EPR imaging methods are lengthy due to the need for multiple acquisitions separated by times comparable to relaxation times T1 and T2, leading to reduced image quality and increased duration, especially when imaging relaxation times T1 and T2.
Innovation Solution
A single-point imaging (SPI) methodology that extends to imaging relaxation times T1 and T2, using a series of radio frequency pulses with equal time intervals and a sequence duration longer than T1, allowing for signal averaging and parameter extraction without saturation by repetition time, combined with phase cycling to separate signals and data fitting using the Bloch equation or pre-measured libraries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple acquisitions with different delays are used to determine relaxation times T1 and T2, then measurement precision is improved, but experiment duration increases significantly
Solution Approach 1:
The patent applies periodic action by using a train of equally spaced RF pulses instead of isolated pulses. The periodic pulse train creates a time-efficient measurement scheme where multiple signal evolutions are captured within a single experiment duration, allowing determination of both T1 and T2 relaxation times without requiring multiple separate acquisitions separated by relaxation periods.
Solution Approach 2:
The patent implements continuity of useful action by continuously acquiring signal evolution data throughout the pulse sequence duration. Rather than stopping between acquisitions to allow equilibration, the method continuously records signals from multiple pulses, maximizing the utilization of the experiment time for productive measurement of relaxation parameters.
2Measurement precision
If conventional pulse EPR sequences are used to determine single parameters, then measurement precision for that parameter is improved, but the overall experiment becomes lengthy due to multiple acquisitions
Solution Approach 1:
The patent applies universality by designing a single pulse sequence that simultaneously determines multiple parameters (T1, T2, and spatial distribution). The same sequence of equally spaced RF pulses generates signal evolutions that contain information about all these parameters, eliminating the need for separate specialized sequences for each parameter and thereby improving experimental productivity.
Solution Approach 2:
The patent utilizes another dimension by exploiting the time dimension within a single pulse sequence. Instead of using multiple sequences separated in time, the method captures multiple signal evolutions at different time points within one continuous sequence, effectively using the temporal dimension to encode multiple measurements that would otherwise require separate experiments.
3Manufacturing precision
If spatial EPR imaging is performed with magnetic field gradients, then spatial resolution is improved, but the number of acquisitions increases resulting in long image duration
Solution Approach 1:
The patent merges spatial encoding with relaxation time measurement by incorporating magnetic field gradients into the pulse sequence that also measures T1 and T2. This combination allows simultaneous acquisition of spatial distribution and relaxation parameters within the same experiment, eliminating the need for separate imaging and relaxation measurements and thereby reducing total acquisition time while maintaining spatial resolution.
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
Enables high-resolution imaging of T1 and T2 without increasing the number of measurements, improving image quality and efficiency by maintaining non-equilibrium conditions and utilizing signal evolution for precise parameter determination.
Implementation Method 1
Electron paramagnetic resonance (EPR), also known as electron spin resonance (ESR), is a magnetic resonance method that observes the unpaired electrons (also referred here as electron spins) under a constant magnetic field. Pulse EPR is a subset of EPR methods that utilizes radiofrequency pulses of alternating magnetic field (B1, also known as the transverse magnetic field) to manipulate electron spins' magnetization.
Implementation Method 2
Pulse EPR imaging (pEPRI) utilizes magnetic field gradients to generate three-dimensional maps of parameters of interest.
Implementation Method 3
Conventional pulse EPR sequences seek to determine a single parameter of interest such as relaxation times T1 or T2
Implementation Method 4
Conventional pulse EPR sequences seek to determine a single parameter of interest such as relaxation times T1 or T2
Data Source
AI summary
A method for relaxation time determination includes delivering a series of radio frequency (RF) pulses in a sequence to a specimen having a magnetic resonance spin system. The pulses are separated by equal time intervals and the sequence has a duration comparable or greater than a spin-lattice relaxation time for the spin system. The method includes receiving a response after each RF pulse in the series. The response includes a free induction decay and spin echoes. The method includes generating a series of single point imaging (SPI) images from each response. Each SPI image of the series corresponds to an RF pulse in the series. The method includes converting SPI images to a spin-spin relaxation map and a spin-lattice relaxation map.