Quantitative oxygen imaging systems and methods using echo-based single point imaging
Inventors
Subramanian, Sankaran • Devasahayam, Nallathamby • Matsumoto, Shingo • Mitchell, James B. • Cherukuri, Murali Krishna • Cook, John A.
Assignees
US Department of Health and Human Services
Publication Number
US-8712499-B2
Publication Date
2014-04-29
Expiration Date
2029-11-25
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
An echo-based single point imaging (ESPI) system (10) providing high-resolution oxygen images of a sample is disclosed. The ESPI system (10) employs spin echo detection of the resonance from a spin probe and concurrent Single Point Imaging (SPI) for spatial encoding of the oxygen concentration within the sample. Images are derived by comparing spin echo intensities of two images reconstructed at two time points selected at identical time intervals on either side of a refocusing pulse, eliminating artifacts associated with sample magnetic susceptibility and field inhomogeneity effects.
Core Innovation
The invention provides an echo-based single point imaging (ESPI) system that produces high-resolution quantitative oxygen images of a sample. This system combines spin echo detection of the resonance from a spin probe with concurrent single point imaging (SPI) for spatial encoding of oxygen concentration within the sample. The technique reconstructs images by comparing spin echo intensities of two images obtained at precisely selected time points symmetric around a refocusing pulse, thus eliminating artifacts caused by sample magnetic susceptibility and magnetic field inhomogeneities.
The problem addressed arises from existing methods where magnetic field inhomogeneity, intrinsic magnetic susceptibility of the sample, and other time-dependent effects degrade the accuracy and spatial resolution of oxygen imaging in vivo. Previous electron paramagnetic resonance (EPR) spin echo Fourier transform imaging techniques provide accurate oxymetric information but with limited spatial resolution, while multi-gradient single point imaging (SPI) approaches offer superior spatial resolution but require careful calibration for oxygen concentration quantification due to sensitivity to magnetic field inhomogeneities.
This invention solves the need for a tissue imaging method that combines the excellent spatial resolution of SPI imaging and the precise oxymetric accuracy of spin echo Fourier transform imaging. By using the ESPI approach with symmetric time point selection around a 180° refocusing pulse, the system obtains high resolution images that reflect true T2 relaxation processes, enabling accurate spatial mapping of oxygen content unaffected by field inhomogeneities or susceptibility artifacts.
Claims Coverage
The patent includes three main independent claims covering methods and systems for producing high-resolution quantitative oxygen images using an echo-based single point imaging approach.
Method of producing high-resolution quantitative oxygen image using echo-based single point imaging system
Determining spatially-resolved relaxivity between logarithms of spin intensities from first and second ESPI images measured at times symmetric around a 180° refocusing pulse; determining spatially-resolved oxygen content by interpolating from a predetermined table relating reference oxygen concentrations to spatially-resolved relaxivity; and mapping oxygen content onto spatial locations to produce the oxygen image.
Method providing at least two high-resolution ESPI images for spatially-resolved oxygen quantification
Providing first and second ESPI images reconstructed from EPR signals measured at times Δt before and after the 180° refocusing pulse; determining spatially-resolved relaxivity between logarithms of spatially-resolved spin intensities in corresponding pixels of the two images; interpolating spatially-resolved oxygen content from a table as a function of relaxivity; and mapping oxygen content spatially to produce a high-resolution image.
System for producing high-resolution quantitative oxygen image including modules executed on a processor
Having an ESPI image comparison module to derive spatially-resolved relaxivity between logarithms of spin intensities from first and second ESPI images; and an oxygen imaging module to determine oxygen concentration by interpolating from a reference table as a function of spatially-resolved relaxivity and map concentrations spatially to produce the high-resolution image.
The claims cover methods and systems for quantitative oxygen imaging employing echo-based single point imaging with symmetric time point acquisitions around a refocusing pulse, accurate determination of spatially-resolved relaxivity from spin intensity logarithms, interpolation of oxygen concentration from reference data, and spatial mapping to generate high-resolution oxygen images.
Stated Advantages
Eliminates artifacts associated with magnetic susceptibility and field inhomogeneity effects on imaging.
Produces high-resolution oxygen images with superior spatial resolution compared to previous methods.
Obtains accurate T2-weighted oxygen quantization unaffected by sample-specific and system-specific factors.
Combines the spatial resolution of single point imaging with the oxymetric accuracy of spin echo Fourier transform imaging.
Enables in vivo functional physiological imaging with high temporal and spatial resolution suitable for observing rapid physiological processes.
Documented Applications
Planning and assessing efficacy of radiation and chemotherapeutic treatment for tumors through in vivo functional physiological imaging of small animals.
Observation of changes in blood perfusion and oxygenation in tumors in near real time and non-invasive analysis of angiogenesis.
Quantification of pharmacokinetics and metabolic degradation kinetics of bioactive free radicals.
Measurement of tissue oxygenation during ischemia and reperfusion.
Characterization of polymers with respect to amorphous and crystalline fractions in materials science and solid state measurements.
Interested in licensing this patent?