Nuclear magnetic resonance systems and methods for noninvasive and in-vivo measurements using a unilateral magnet
An apparatus for non-invasive evaluations and in-vivo diagnostics includes an open magnet, an RF antenna, and an NMR analytics logical circuit communicatively coupled to the RF antenna, wherein the open magnet is shaped to generate a static magnetic field that extends unilaterally into an object or internal organ of a subject when the open magnet is positioned against or in proximity to the object or subject, the static and RF magnetic fields shaped to generate a sensitive volume within a target region. The RF antenna or antenna array is configured to transmit RF pulses into the target region of the object or internal organ and receive sets of NMR signals generated by hydrogen or other elements, and the NMR analytics logical circuit is configured to obtain and analyze sets of NMR signals.
1. An RF circuit for a NMR apparatus, the circuit comprising:
a transceiver, a processor, and a non-transitory computer-readable medium with computer instruction embedded thereon to cause the processor to:
generate an RF pulse sequence comprising dedicated J-coupling pulse sequences, each dedicated J-coupling pulse sequence selected to have a pulse spacing and a pulse duration corresponding to a reduction of a signal component based on a desired proton spectral shift and a characteristic J-coupling time scale;
instruct the transceiver to:
transmit RF pulses in accordance with the generated RF pulse sequence into a target region;
receive a first set of NMR signals generated by a first set of atomic nuclei from a first substance as the first set of nuclei realign their spin axes to the magnetic field after being stimulated by the RF pulses; and
receive a second set of NMR signals generated by a second set of atomic nuclei from a second substance as the second set of nuclei realign their spin axes to the magnetic field after being stimulated by the RF pulses;
obtain the first and second sets of NMR signals from the transceiver;
perform a discrete multi-component analysis of the NMR signals to determine a first set of measured NMR relaxation times and a first diffusion parameter from the first set of NMR signals, and a second set of measured NMR relaxation times and a second diffusion parameter from the second set of NMR signals;
quantify and characterize the first and second substances based on a multi-component analysis of the first and second sets of NMR signals by performing a J-coupling analysis of the NMR signals based on a distinctive response of the first set of NMR signals and the second set of NMR signals to RF pulse sequences as determined by resolving independent relationships of the NMR signals at pulse sequence times, t, to determine a first component contribution, C 1 , corresponding to the first substance and second component contribution, C 2 , corresponding to the second substance, as follows:
S ( t )= C 1 e t/T2eff 1 +C 2 e t/T2eff 2 +C 0 ;
1 /T 2 eff 1 =1 /T 2 1 +A 1 TE 2 ; and
1 /T 2 eff 2 =1 /T 2 2 +A 2 TE 2 ; and
wherein C 0 is a baseline signal, TE is an inter-spin echo duration time, the first diffusion parameter is proportional to A 1 , the second diffusion parameter is proportional to A 1 , the first set of measured NMR relaxation times is proportional to T2eff 1 , the second set of measured NMR relaxation times is proportional to T2eff 2 , T2 1 is the spin-spin relaxation time of the first substance, and T2 2 is the spin-spin relaxation time of the second substance; and
issue instructions to display a characterization of the first and second substances in a graphical user interface.
2. The circuit of claim 1 , wherein the computer instructions further cause the processor to quantify a concentration of the first substance based on a discrete multi-component signal decay analysis of the first and second NMR signals.
3. The circuit of claim 1 , further comprising an RF antenna, wherein the RF antenna comprises an open coil and is configured to transmit RF pulses in a substantially perpendicular orientation to the static magnetic field.
4. The circuit of claim 3 , wherein the RF antenna further comprises an array of sub-antennas.
5. The circuit of claim 4 , wherein the computer instructions further cause the processor to calculate and to plot, on the graphical user interface, a 2-dimensional distribution of T2 relaxation times and diffusion parameters from the first and second sets of NMR signals.
6. The circuit of claim 1 , wherein the computer instructions further cause the processor to calculate and to plot, on the graphical user interface, a 2-dimensional distribution of T1 relaxation times and diffusion parameters from the first and second sets of NMR signals.
7. The circuit of claim 1 , wherein the computer instructions further cause the processor circuit is further configured to determine a fat concentration based on a ratio of the amplitude of the first set of NMR signals as compared with the amplitude of the second set of NMR signals.
8. The circuit of claim 1 , wherein the computer instructions further cause the processor circuit to detect liver fibrosis based on a ratio of the amplitude of the first set of NMR signals as compared with the amplitude of the second set of NMR signals.
9. The circuit of claim 1 , wherein the computer instructions further cause the processor to obtain, from an NMR signal database, a calibration signal amplitude for fat in an organ and determine an absolute fat concentration based on a ratio of the amplitude of the first set of NMR signals as compared with the calibration signal.
10. An NMR detection method comprising:
generating an RF pulse sequence comprising dedicated J-coupling pulse sequences, each dedicated J-coupling pulse sequence selected to have a pulse spacing and a pulse duration corresponding to a reduction of a signal component based on a desired proton spectral shift and a characteristic J-coupling time scale;
transmitting RF pulses in accordance with the generated RF pulse sequence into the target region;
receiving a first set of NMR signals generated by a first set of atomic nuclei from a first substance as the first set of nuclei realign their spin axes to the magnetic field after being stimulated by the RF pulses;
receiving a second set of NMR signals generated by a second set of atomic nuclei from a second substance as the second set of nuclei realign their spin axes to the magnetic field after being stimulated by the RF pulses; and
obtaining, with an RF circuit, the first and second sets of NMR signals, wherein a total signal amplitude of the NMR signals at a pulse sequence time, t, is represented as a discrete distribution of the NMR signals;
characterizing, with the RF circuit, the first and second substances based on a multi-component analysis of the NMR signals; and
performing, with the RF circuit, a discrete multi-component analysis of the NMR signals by determining a first set of measured NMR relaxation times and a first diffusion parameter from the first set of NMR signals, and a second set of measured NMR relaxation times and a second diffusion parameter from the second set of NMR signals;
wherein performing the substance characterization comprises performing a J-coupling analysis of the NMR signals based on a distinctive response of the first set of NMR signals and the second set of NMR signals to RF pulse sequences as determined by resolving independent relationships of the NMR signals at pulse sequence times, t, to determine a first component contribution, C1, corresponding to the first substance and second component contribution, C2, corresponding to the second substance, as follows;
S ( t )= C 1 e t/T2eff 1 +C 2 e t/T2eff 2 +C 0 ;
1 /T 2 eff 1 =1 /T 2 1 +A 1 TE 2 ; and
1 /T 2 eff 2 =1 /T 2 2 +A 2 TE 2 ; and
wherein C 0 is a baseline signal, TE is an inter-spin echo duration time, the first diffusion parameter is proportional to A 1 , the second diffusion parameter is proportional to A 1 , the first set of measured NMR relaxation times is proportional to T2eff 1 , the second set of measured NMR relaxation times is proportional to T2eff 2 , T2 1 is the spin-spin relaxation time of the first substance, and T2 2 is the spin-spin relaxation time of the second substance; and
displaying a characterization of the first and second substances in a graphical user interface.
11. The method of claim 10 , further comprising quantifying a concentration of the first substance based on a discrete multi-component signal decay analysis of the first and second NMR signals.
12. The method of claim 10 , further comprising transmitting RF pulses in a substantially perpendicular orientation to the static magnetic field.
13. The method of claim 10 , further comprising calculating and plotting, on a graphical user interface, a 2-dimensional distribution of T2 relaxation times and diffusion parameters from the first and second sets of NMR signals.
14. The method of claim 10 , further comprising calculating and plotting, on a graphical user interface, a 2-dimensional distribution of T1 relaxation times and diffusion parameters from the first and second sets of NMR signals.
15. The method of claim 10 , further comprising determining a fat concentration based on a ratio of the amplitude of the first set of NMR signals as compared with the amplitude of the second set of NMR signals.
16. The method of claim 10 , further comprising detecting liver fibrosis based on a ratio of the amplitude of the first set of NMR signals as compared with the amplitude of the second set of NMR signals.
17. The method of claim 10 , further comprising obtaining, from an NMR signal database, a calibration signal amplitude for fat in an organ and determine an absolute fat concentration based on a ratio of the amplitude of the first set of NMR signals as compared with the calibration signal.