Method for measuring oil-water distribution using dynamic nuclear polarization for magnetic resonance imaging (DNP-MRI)

Abstract

A method for measuring oil-water distribution using DNP-MRI, comprising adding a free radical for DNP enhanced NMR signal of a water phase or an oil phase in a sample containing oil and water; performing an MRI experiment on the sample, and collecting an MRI image of the sample without DNP enhancement; applying microwave excitation for DNP-MRI experiment under the same MRI experiment condition as step 2, and collecting an MRI image of the sample after DNP enhancement; and comparing the MRI image after DNP enhancement with the MRI image without DNP enhancement. In the MRI image with DNP enhancement, an area with enhanced MRI signal intensity is a selectively enhanced fluid phase distribution area, and an area without obviously changed MRI signal intensity is a non-selectively enhanced fluid phase distribution area. The method is simple, convenient to operate, short in measurement time, and high in measurement efficiency.

Claims

1. A method for measuring oil-water distribution using DNP-MRI, comprising: (1) adding a free radical for DNP-enhanced NMR signal of a water phase or an oil phase in a sample comprising oil and water; (2) performing an MRI on the sample and collecting an MRI image of sample without DNP enhancement; (3) applying microwave excitation for a DNP-MRI under same MRI condition as step (2) and collecting an MRI image of the sample after DNP enhancement; and (4) comparing the MRI image after DNP enhancement with the MRI image without DNP enhancement, wherein in the MRI image after DNP enhancement, an area with enhanced MRI signal intensity is a selectively enhanced fluid phase distribution area, and an area without obviously changed MRI signal intensity is a non-selectively enhanced fluid phase distribution area.

2. The method for measuring oil-water distribution using DNP-MRI according to claim 1, wherein the free radical is a non-selective free radical that is able to simultaneously enhance NMR signals of both the water phase and the oil phase; if only the NMR signal of the water phase needs to be enhanced, a relaxation reagent that is able to enhance relaxation of the oil phase is added; and if only the NMR signal of the oil phase needs to be enhanced, a relaxation reagent that is able to enhance relaxation of the water phase is added.

3. The method for measuring oil-water distribution using DNP-MRI according to claim 1, wherein the free radical is a selective free radical that is able to enhance the NMR signal of the water phase or the oil phase by DNP; if it is required to enhance the NMR signal of the water phase, a selective free radical that is able to enhance the NMR signal of the water phase by DNP is added; and if it is required to enhance the NMR signal of the oil phase, a selective free radical that is able to enhance the NMR signal of the oil phase is added.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a glass bead model.

(2) FIG. 2 is a schematic diagram of a spin echo pulse sequence containing microwave excitation.

(3) FIG. 3 is an MRI image of a glass bead model without DNP enhancement.

(4) FIG. 4 is an MRI image of a glass bead model after DNP enhancement.

(5) FIG. 5 is a difference image between an MRI image of a glass bead model without DNP enhancement and an MRI image of a glass bead model after DNP enhancement.

(6) Reference numbers are used as referring to the following structure: 1—quartz tube, 2—glass bead.

DETAILED DESCRIPTION OF THE INVENTION

(7) The invention is described in detail with reference to the accompanying drawings.

Example 1

(8) 1. A glass bead model is made to simulate a porous material containing oil and water. The glass bead model (as shown in FIG. 1) is made as follows: taking a 10 mm quartz tube 1 having one end open and the other end closed; randomly stacking glass beads 2 with a particle size of 3-5 mm in the 10 mm quartz tube; and soaking the glass beads in the quartz tube layer by layer with water containing a relaxation reagent MnCl.sub.2 and a mineral oil containing a free radical TEMPO (2,2,6,6-Tetramethylpiperidine 1-oxyl), wherein the upper layer is an oil phase, and the lower layer is a water phase, the TEMPO can enhance the NMR signal of the oil phase via DNP, and MnCl.sub.2 can enhance the relaxation of the water phase, and suppress the DNP-NMR signal of the water phase.

(9) 2. The glass bead model is placed in a sample area of a 0.06T DNP magnetic resonance imaging system, where a static magnetic field is provided by a permanent magnet, a resonant cavity used to excite electronic resonance can provide a cylindrical sample space with a diameter of 10 mm and a height of 22 mm, and the glass bead model is located in the center of the magnetic field.

(10) 3. A conventional MRI experiment without DNP enhancement is performed as follows:

(11) 3.1. setting experimental parameters and starting a test, wherein a spin echo pulse sequence (SE) is used and test parameters were as follows: FOV: 30×30 mm, AcquMatrix=128×128, TE=50 ms, number of scan NS=4; an imaging position is sagittal, and an imaging slice is selected;

(12) 3.2. at the end of the experiment, performing image reconstruction, recording a reconstruction result as matrix1, and mapping the reconstruction result to a grayscale image to obtain an MRI image of the glass bead model without DNP enhancement, as shown in FIG. 3.

(13) 4. A DNP-MRI experiment is performed as follows:

(14) 4.1. setting experimental parameters and starting a test, wherein a spin echo pulse sequence containing microwave excitation (DNP-SE) is used and as shown in FIG. 2, test parameters are as follows: FOV: 30×30 mm, AcquMatrix=128×128, TE=50 ms, number of scan NS=1, microwave irradiation time is 1 s, and microwave power is 50 W; an imaging position is sagittal, and an imaging slice (consistent with the imaging slice in step 3) is selected;

(15) 4.2. at the end of the test, performing image reconstruction, recording a reconstruction result as matrix2, and mapping the reconstruction result to a grayscale image to obtain an MRI image of the glass bead model after DNP enhancement, as shown in FIG. 4.

(16) 5. A difference between the reconstruction results matrix1 and matrix2 obtained in step 3.2 and step 4.2 is obtained and mapped to a grayscale image to obtain a difference image, as shown in FIG. 5. An image of the glass bead model without DNP enhancement serves as a reference image and is compared with FIG. 3. As shown in FIG. 4, the MRI signal intensity at the bottom of the quartz tube is greatly reduced or even almost disappears, while the MRI signal at the upper part of the quartz tube is further enhanced rather than being weakened, indicating that the water is distributed at the bottom of the quartz tube and oil is distributed at the upper part of the quartz tube. The grayscale image shown in FIG. 5 is an oil distribution image.