Apparatus, system, method and computer-readable medium for isolating chemical exchange saturation transfer contrast from magnetization transfer asymmetry under two-frequency RF irradiation

Patent metadata

Field	Value
Publication number	US-9709511-B2
Application number	US-201213687342-A
Country	US
Kind code	B2
Filing date	Nov 28, 2012
Priority date	Nov 28, 2011
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

Apparatus, system, method and computer-readable medium for isolating chemical exchange saturation transfer contrast from magnetization transfer asymmetry under two-frequency RF irradiation. A two-pool model for magnetization transfer (MT) can be established fully based on Provotorov's theory of saturation, and then extended to the situation of simultaneous two-frequency RF irradiation. Numerical simulations and experimental results demonstrate that two-frequency RF irradiation can make MT effects independent of irradiation frequency over a wide range, and thus can suppress MT asymmetry. Exemplary embodiments can be provided to isolate chemical exchange saturation transfer (CEST) contrast from MT asymmetry contrast by using the two-frequency RF irradiation technique. A further embodiment can isolate a narrow-frequency spectrum MT mechanism from a broad-frequency spectrum MT mechanism.

First claim

What is claimed is:

1. A non-transitory computer-readable medium having stored thereon computer-executable instructions for isolating a chemical exchange saturation transfer (CEST), wherein, when a computer hardware arrangement executes the instructions, the computer arrangement is configured to perform procedures comprising:
determining a first frequency based on a resonance frequency of a CEST agent and a second frequency that is outside a typical range of chemical shifts for observed nuclear spins;
determining at least one of a main solvent or a medium for a sample;
causing an irradiation on the sample with both the first and second frequencies using a magnetic resonance (MR) apparatus;
receiving first data based on a first residual polarization of the irradiation of the sample with both the first and second frequencies;
determining third and fourth frequencies that are located symmetrically to the first and second frequencies, respectively, based on a resonance frequency of the at least one of the main solvent or the medium, wherein the at least one of the main solvent or the medium includes a molecule with an exchangeable nuclei;
causing an irradiation of the sample with both the third and fourth frequencies using the MR apparatus;
receiving second data based on a second residual polarization of the irradiation of the sample with both the third and fourth frequencies; and
determining third data related to a CEST contrast by subtracting the first data from the second data.

2. The computer-readable medium of claim 1 , wherein the second frequency is more than about 5 parts per million away from the at least one of the main solvent or the medium.

3. The computer-readable medium of claim 1 , wherein the second frequency causes magnetization transfer (MT) effects such that spins causing MT experience substantially simultaneous saturation by two frequencies.

4. The computer-readable medium of claim 3 , wherein the MT effects are uniform over a frequency range.

5. The computer-readable medium of claim 4 , wherein MT effects are used as an image contrast mechanism.

6. The computer-readable medium of claim 5 , wherein the image contrast mechanism is robust against B0 and B1 inhomogeneities.

7. The computer-readable medium of claim 1 , wherein the third and fourth frequencies are located substantially away from the first and second frequencies.

8. The computer-readable medium of claim 7 , wherein the third and fourth frequencies are within a range of a spectrum of spins causing MT effects such that the spins experience substantially simultaneous saturation by the third and fourth frequencies.

9. The computer-readable medium of claim 1 , wherein the subtracting of the first data from the second data reduces or eliminates a contribution of one of at least a direct solvent or medium saturation due to a pair-wise symmetric configuration.

10. The computer-readable medium of claim 1 , wherein subtracting eliminates an MT contribution.

11. The computer-readable medium of claim 1 , further comprising:
determining at least one further frequency;
receiving further data based on at least one further residual polarization of at least one further irradiation of the sample with the at least one further frequency; and
refining the CEST contrast by separating different exchange mechanisms.

12. The computer-readable medium of claim 1 , wherein the at least one of the main solvent or the medium is at least one of water or alcohol.

13. A non-transitory computer-readable medium having stored thereon computer-executable instructions for removing Magnetization (MT) asymmetry and correcting magnetic field (B0) inhomogeneity, wherein, when a computer hardware arrangement executes the instructions, the computer arrangement is configured to perform procedures comprising:
determining a first frequency based on a resonance frequency of a chemical exchange saturation transfer (CEST) agent and a second frequency that is outside a typical range of chemical shifts for observed nuclear spins;
causing an irradiation on a sample with (i) a fourth frequency corresponding to a difference f d between the first frequency and the second frequency, and (ii) a third frequency, equal to a half sum f 0 of the first frequency and the second frequency using a magnetic resonance apparatus;
receiving first data based on a irradiation of the sample; and
determining second data based on a residual polarization of the first data.

14. The computer-readable medium of claim 13 , wherein values of the third and fourth frequency values are measured with respect to at least one of a solvent or a medium nuclear spin resonance frequency.

15. The computer-readable medium of claim 13 , further comprising:
modifying f 0 to a new value f1 within about −f d and f d ;
receiving third data based on at least one further simultaneous irradiation with frequencies based on f1; and
generating visual information associated with the residual polarization against f 0 .

16. The computer-readable medium of claim 15 , further comprising constructing a B0 map.

17. The computer-readable medium of claim 16 , further comprising identifying two local minima on a plot corresponding to direct saturation of at least one of a main solvent or a medium nuclear spin resonance frequency, and averaging two frequencies respectively at the two local minima.

18. The computer-readable medium of claim 17 , further comprising quantifying a precision estimate for at least one of the main solvent or the medium nuclear spin resonance frequency as f d minus an average of the two frequencies respectively at the two local minima.

19. The computer-readable medium of claim 18 , further comprising correcting a CEST contrast, including shifting the plot by the average of the two frequencies respectively at the two local minima to center on zero.

20. A method for isolating a chemical exchange saturation transfer (CEST):
determining a first frequency based on a resonance frequency of a CEST agent and a second frequency that is outside a typical range of chemical shifts for observed nuclear spins;
determining at least one of a main solvent or a medium for a sample;
irradiating the sample with both the first and second frequencies using a magnetic resonance (MR) apparatus;
receiving first data based on a first residual polarization of the irradiation of the sample with both the first and second frequencies;
determining third and fourth frequencies that are located symmetrically to the first and second frequencies, respectively, based on a resonance frequency of the at least one of the main solvent or the medium, wherein the at least one of the main solvent or the medium includes a molecule with an exchangeable nuclei;
irradiating the sample with both the third and fourth frequencies using the MR apparatus receiving second data based on a second residual polarization of the irradiation of the sample with both the third and fourth frequencies; and
using a computer hardware arrangement, determining third data related to a CEST contrast by subtracting the first data from the second data.

21. The method of claim 20 , wherein the at least one of the main solvent or the medium is at least one of water or alcohol.

22. A system for substantially isolating a chemical exchange saturation transfer (CEST), comprising:
a hardware processing arrangement configured to:
determine a first frequency based on a resonance frequency of a CEST agent and a second frequency that is

Assignees

• Univ New York

Inventors

• Lee Jae Seung
• Regatte Ravinder R
• Jerschow Alexej

Classifications

• G06F19/707

  Physics · mapped topic

• G01N23/02 Primary

  by transmitting the radiation through the material · CPC title

• G01R33/5605 Primary

  by transferring coherence or polarization from a spin species to another, e.g. creating magnetization transfer contrast [MTC], polarization transfer using nuclear Overhauser enhancement [NOE] · CPC title

• G16C20/70

  Machine learning, data mining or chemometrics · CPC title